Virtual Private Routed Network service

eiBGP load balancing allows a route to have multiple next hops of different types, using both IPv4 next hops and MPLS LSPs simultaneously.

Basic eiBGP topology displays a basic topology that could use eiBGP load balancing. In this topology CE1 is dual homed and therefore reachable by two separate PE routers. CE 2 (a site in the same VPRN) is also attached to PE1. With eiBGP load balancing, PE1 uses its own local IPv4 nexthop as well as the route advertised by MP-BGP, by PE2.

Another example displayed in Extranet load balancing shows an extra net VPRN (VRF). The traffic ingressing the PE that should be load balanced is part of a second VPRN and the route over which the load balancing is to occur is part of a separate VPRN instance and are leaked into the second VPRN by route policies.

Here, both routes can have a source protocol of VPN-IPv4 but one still has an IPv4 nexthop and the other can have a VPN-IPv4 nexthop pointing out a network interface. Traffic is still load balanced (if eiBGP is enabled) as if only a single VRF was involved.

Traffic is load balanced across both the IPv4 and VPN-IPv4 next hops. This helps to use all available bandwidth to reach a dual-homed VPRN.

Routing information learned from the CE-to-PE routing protocols and configured static routes should be injected in the associated local VPN routing/forwarding (VRF). In the case of dynamic routing protocols, there may be protocol specific route policies that modify or reject specific routes before they are injected into the local VRF.

Route redistribution from the local VRF to CE-to-PE routing protocols is to be controlled via the route policies in each routing protocol instance, in the same manner that is used by the base router instance.

The advertisement or redistribution of routing information from the local VRF to or from the MP-BGP instance is specified per VRF and is controlled by VRF route target associations or by VRF route policies.

VPN-IP routes imported into a VPRN, have the protocol type bgp-vpn to denote that it is an VPRN route. This can be used within the route policy match criteria.

Static routes are used within many IES services and VPRN services. Unlike dynamic routing protocols, there is no way to change the state of routes based on availability information for the associated CPE. CPE connectivity check adds flexibility so that unavailable destinations are removed from the VPRN routing tables dynamically and minimize wasted bandwidth. Directly connected IP target shows a setup with a directly connected IP target and Multiple hops to IP target shows a setup with multiple hops to an IP target.

The availability of the far-end static route is monitored through periodic polling. The polling period is configured. If the poll fails a specified number of sequential polls, the static route is marked as inactive.

Either ICMP ping or unicast ARP mechanism can be used to test the connectivity. ICMP ping is preferred.

If the connectivity check fails and the static route is deactivated, the router continues to send polls and re-activate any routes that are restored.

Constrained Route Distribution (or RT Constraint) is a mechanism that allows a router to advertise Route Target membership information to its BGP peers to indicate interest in receiving only VPN routes tagged with specific Route Target extended communities. Upon receiving this information, peers restrict the advertised VPN routes to only those requested, minimizing control plane load in terms of protocol traffic and possibly also RIB memory.

The Route Target membership information is carried using MP-BGP, using an AFI value of 1 and SAFI value of 132. In order for two routers to exchange RT membership NLRI they must advertise the corresponding AFI/SAFI to each other during capability negotiation. The use of MP-BGP means RT membership NLRI are propagated, loop-free, within an AS and between ASes using well-known BGP route selection and advertisement rules.

ORF can also be used for RT-based route filtering, but ORF messages have a limited scope of distribution (to direct peers) and therefore do not automatically create pruned inter-cluster and inter-AS route distribution trees.

RT Constraint is supported only by the base router BGP instance. When the family command at the BGP router group or neighbor CLI context includes the route-target keyword, the RT Constraint capability is negotiated with the associated set of EBGP and IBGP peers.

ORF and RT Constraint are mutually exclusive on a particular BGP session. The CLI does not attempt to block this configuration, but if both capabilities are enabled on a session, the ORF capability is not included in the OPEN message sent to the peer.

When the base router has one or more RTC peers (BGP peers with which the RT Constraint capability has been successfully negotiated), one RTC route is created for each RT extended community imported into a locally-configured L2 VPN or L3 VPN service. These imported route targets are configured in the following contexts:

• config>service>vprn

• config>service>vprn>mvpn

By default, these RTC routes are automatically advertised to all RTC peers, without the need for an export policy to explicitly ‟accept” them. Each RTC route has a prefix, a prefix length and path attributes. The prefix value is the concatenation of the origin AS (a 4-byte value representing the 2- or 4-octet AS of the originating router, as configured using the config>router>autonomous-system command) and 0 or 16-64 bits of a route target extended community encoded in one of the following formats: 2-octet AS specific extended community, IPv4 address specific extended community, or 4-octet AS specific extended community.

A router may be configured to send the default RTC route to any RTC peer. This is done using the new default-route-target group/neighbor CLI command. The default RTC route is a special type of RTC route that has zero prefix length. Sending the default RTC route to a peer conveys a request to receive all VPN routes (regardless of route target extended community) from that peer. The default RTC route is typically advertised by a route reflector to its clients. The advertisement of the default RTC route to a peer does not suppress other more specific RTC routes from being sent to that peer.

All received RTC routes that are deemed valid are stored in the RIB-IN. An RTC route is considered invalid and treated as withdrawn, if any of the following applies:

• The prefix length is 1-31.

• The prefix length is 33-47.

• The prefix length is 48-96 and the 16 most-significant bits are not 0x0002, 0x0102 or 0x0202.

If multiple RTC routes are received for the same prefix value then standard BGP best path selection procedures are used to determine the best of these routes.

The best RTC route per prefix is re-advertised to RTC peers based on the following rules:

• The best path for a default RTC route (prefix-length 0, origin AS only with prefix-length 32, or origin AS plus 16 bits of an RT type with prefix-length 48) is never propagated to another peer.

• A PE with only IBGP RTC peers that is neither a route reflector nor an ASBR does not re-advertise the best RTC route to any RTC peer because of standard IBGP split horizon rules.

• A route reflector that receives its best RTC route for a prefix from a client peer re-advertises that route (subject to export policies) to all of its client and non-client IBGP peers (including the originator), per standard RR operation. When the route is re-advertised to client peers, the RR (i) sets the ORIGINATOR_ID to its own router ID and (ii) modifies the NEXT_HOP to be its local address for the sessions (for example, system IP).

• A route reflector that receives its best RTC route for a prefix from a non-client peer re-advertises that route (subject to export policies) to all of its client peers, per standard RR operation. If the RR has a non-best path for the prefix from any of its clients, it advertises the best of the client-advertised paths to all non-client peers.

• An ASBR that is neither a PE nor a route reflector that receives its best RTC route for a prefix from an IBGP peer re-advertises that route (subject to export policies) to its EBGP peers. It modifies the NEXT_HOP and AS_PATH of the re-advertised route per standard BGP rules. No aggregation of RTC routes is supported.

• An ASBR that is neither a PE nor a route reflector that receives its best RTC route for a prefix from an External Border Gateway Protocol (EBGP) peer re-advertises that route (subject to export policies) to its EBGP and IBGP peers. When re-advertised routes are sent to EBGP peers, the ASBR modifies the NEXT_HOP and AS_PATH per standard BGP rules. No aggregation of RTC routes is supported.

In general (ignoring IBGP-to-IBGP rules, Add-Path, Best-external, and so on), the best VPN route for every prefix/NLRI in the RIB is sent to every peer supporting the VPN address family, but export policies may be used to prevent some prefix/NLRI from being advertised to specific peers. These export policies may be configured statically or created dynamically based on use of ORF or RT constraint with a peer. ORF and RT Constraint are mutually exclusive on a session.

When RT Constraint is configured on a session that also supports VPN address families using route targets (that is: vpn-ipv4, vpn-ipv6, l2-vpn, mvpn-ipv4, mvpn-ipv6, mcast-vpn-ipv4 or evpn), the advertisement of the VPN routes is affected as follows:

1. When the session comes up, the advertisement of the VPN routes is delayed for a short while to allow RTC routes to be received from the peer.

2. After the initial delay, the received RTC routes are analyzed and acted upon. If S1 is the set of routes previously advertised to the peer and S2 is the set of routes that should be advertised based on the most recent received RTC routes, the following applies:

   • The set of routes in S1 but not in S2 should be withdrawn immediately (subject to MRAI).

   • The set of routes in S2 but not in S1 should be advertised immediately (subject to MRAI).

If a default RTC route is received from a peer P1, the VPN routes that are advertised to P1 is the set that meets all of the following requirements:

• The set is eligible for advertisement to P1 per BGP route advertisement rules.

• The set has not been rejected by manually configured export policies.

• The set has not been advertised to the peer.

In this context, a default RTC route is any of the following:

• a route with NLRI length = zero

• a route with NLRI value = origin AS and NLRI length = 32

• a route with NLRI value = {origin AS+0x0002 | origin AS+0x0102 | origin AS+0x0202} and NLRI length = 48

  • If an RTC route for prefix A (origin-AS = A1, RT = A2/n, n > 48) is received from an IBGP peer I1 in autonomous system A1, the VPN routes that are advertised to I1 is the set that meets all of the following requirements:

    • The set is eligible for advertisement to I1 per BGP route advertisement rules.

    • The set has not been rejected by manually configured export policies.

    • The set carries at least one route target extended community with value A2 in the n most significant bits.

    • The set has not been advertised to the peer.

    Note: This applies whether I1 advertised the best route for A or not.

  • If the best RTC route for a prefix A (origin-AS = A1, RT = A2/n, n > 48) is received from an IBGP peer I1 in autonomous system B, the VPN routes that are advertised to I1 is the set that meets all of the following requirements:

    • The set is eligible for advertisement to I1 per BGP route advertisement rules.

    • The set has not been rejected by manually configured export policies.

    • The set carries at least one route target extended community with value A2 in the n most significant bits.

    • The set has not been advertised to the peer.

    Note: This applies only if I1 advertised the best route for A.

  • If the best RTC route for a prefix A (origin-AS = A1, RT = A2/n, n > 48) is received from an EBGP peer E1, the VPN routes that are advertised to E1 is the set that meets all of the following requirements:

    • The set is eligible for advertisement to E1 per BGP route advertisement rules.

    • The set has not been rejected by manually configured export policies.

    • The set carries at least one route target extended community with value A2 in the n most significant bits.

    • The set has not been advertised to the peer.

    Note: This applies only if E1 advertised the best route for A.

In a VPRN context, BGP fast reroute is optional and must be enabled. Fast reroute can be applied to all IPv4 prefixes, all IPv6 prefixes, all IPv4 and IPv6 prefixes, or to a specific set of IPv4 and IPv6 prefixes.

If all IP prefixes require backup path protection, use a combination of the BGP instance-level backup-path and VPRN-level enable-bgp-vpn-backup commands. The VPRN BGP backup-path command enables BGP fast reroute for all IPv4 prefixes or all IPv6 prefixes, or both, that have a best path through a VPRN BGP peer. The VPRN-level enable-bgp-vpn-backup command enables BGP fast reroute for all IPv4 prefixes or all IPv6 prefixes, or both, that have a best path through a remote PE peer.

If only some IP prefixes require backup path protection, use route policies to apply the install-backup-path action to the best paths of the IP prefixes requiring protection. See the ‟BGP Fast Reroute” section of the 7450 ESS, 7750 SR, 7950 XRS, and VSR Unicast Routing Protocols Guide for more information.

This section discusses QPPB as it applies to VPRN, IES, and router interfaces. See the QoS Policy Propagation Using BGP (QPPB) section and the IP Router Configuration section in the 7450 ESS, 7750 SR, 7950 XRS, and VSR Router Configuration Guide.

The QoS Policy Propagation Using BGP (QPPB) feature applies only to the 7450 ESS and 7750 SR.

QoS policy propagation using BGP (QPPB) is a feature that allows a route to be installed in the routing table with a forwarding-class and priority so that packets matching the route can receive the associated QoS. The forwarding-class and priority associated with a BGP route are set using BGP import route policies. In the industry, this feature is called QPPB, and even though the feature name refers to BGP specifically. On SR OS, QPPB is supported for BGP (IPv4, IPv6, VPN-IPv4, VPN-IPv6), RIP and static routes.

While SAP ingress and network QoS policies can achieve the same end result as QPPB, the effort involved in creating the QoS policies, keeping them up-to-date, and applying them across many nodes is much greater than with QPPB. This is because of assigning a packet, arriving on a particular IP interface, to a specific forwarding-class and priority/profile, based on the source IP address or destination IP address of the packet. In a typical application of QPPB, a BGP route is advertised with a BGP community attribute that conveys a particular QoS. Routers that receive the advertisement accept the route into their routing table and set the forwarding-class and priority of the route from the community attribute.

The typical applications of QPPB are as follows:

• coordination of QoS policies between different administrative domains

• traffic differentiation within a single domain, based on route characteristics

The operator of an administrative domain A can use QPPB to signal to a peer administrative domain B that traffic sent to specific prefixes advertised by domain A should receive a particular QoS treatment in domain B. More specifically, an ASBR of domain A can advertise a prefix XYZ to domain B and include a BGP community attribute with the route. The community value implies a particular QoS treatment, as agreed by the two domains (in their peering agreement or service level agreement, for example). When the ASBR and other routers in domain B accept and install the route for XYZ into their routing table, they apply a QoS policy on selected interfaces that classifies traffic toward network XYZ into the QoS class implied by the BGP community value.

QPPB may also be used to request that traffic sourced from specific networks receive appropriate QoS handling in downstream nodes that may span different administrative domains. This can be achieved by advertising the source prefix with a BGP community, as discussed above. However, in this case other approaches are equally valid, such as marking the DSCP or other CoS fields based on source IP address so that downstream domains can take action based on a common understanding of the QoS treatment implied by different DSCP values.

In the above examples, coordination of QoS policies using QPPB could be between a business customer and its IP VPN service provider, or between one service provider and another.

There may be times when a network operator wants to provide differentiated service to certain traffic flows within its network, and these traffic flows can be identified with known routes. For example, the operator of an ISP network may want to give priority to traffic originating in a particular ASN (the ASN of a content provider offering over-the-top services to the ISP’s customers), following a specific AS_PATH, or destined for a particular next-hop (remaining on-net vs. off-net).

Use of QPPB to differentiate traffic in an ISP network shows an example of an ISP that has an agreement with the content provider managing AS300 to provide traffic sourced and terminating within AS300 with differentiated service appropriate to the content being transported. In this example we presume that ASBR1 and ASBR2 mark the DSCP of packets terminating and sourced, respectively, in AS300 so that other nodes within the ISP’s network do not need to rely on QPPB to determine the correct forwarding-class to use for the traffic. The DSCP or other CoS markings could be left unchanged in the ISP’s network and QPPB used on every node.

There are two main aspects of the QPPB feature on the 7450 ESS and 7750 SR:

• the ability to associate a forwarding-class and priority with specific routes in the routing table

• the ability to classify an IP packet arriving on a particular IP interface to the forwarding-class and priority associated with the route that best matches the packet

This feature uses the fc command in the route-policy hierarchy to set the forwarding class and optionally the priority associated with routes accepted by a route-policy entry. The command has the following structure:

fc fc-name [priority {low | high}]

The use of this command is illustrated by the following example:

config>router>policy-options
begin
community gold members 300:100
policy-statement qppb_policy
entry 10
from
protocol bgp
community gold
exit
action accept
fc h1 priority high
exit
exit
exit
commit

The fc command is supported with all existing from and to match conditions in a route policy entry and with any action other than reject, it is supported with next-entry, next-policy and accept actions. If a next-entry or next-policy action results in multiple matching entries then the last entry with a QPPB action determines the forwarding class and priority.

A route policy that includes the fc command in one or more entries can be used in any import or export policy, but the fc command has no effect except in the following types of policies:

• VRF import policies

  • config>service>vprn>vrf-import

• BGP import policies

  • config>router>bgp>import

  • config>router>bgp>group>import

  • config>router>bgp>group>neighbor>import

  • config>service>vprn>bgp>import

  • config>service>vprn>bgp>group>import

  • config>service>vprn>bgp>group>neighbor>import

• RIP import policies

  • config>router>rip>import

  • config>router>rip>group>import

  • config>router>rip>group>neighbor>import

  • config>service>vprn>rip>import

  • config>service>vprn>rip>group>import

  • config>service>vprn>rip>group>neighbor>import

As evident from above, QPPB route policies support routes learned from RIP and BGP neighbors of a VPRN as well as for routes learned from RIP and BGP neighbors of the base/global routing instance.

QPPB is supported for BGP routes belonging to any of the address families listed below:

• IPv4 (AFI=1, SAFI=1)

• IPv6 (AFI=2, SAFI=1)

• VPN-IPv4 (AFI=1, SAFI=128)

• VPN-IPv6 (AFI=2, SAFI=128)

A VPN-IP route may match both a VRF import policy entry and a BGP import policy entry (if vpn-apply-import is configured in the base router BGP instance). In this case the VRF import policy is applied first and then the BGP import policy, so the QPPB QoS is based on the BGP import policy entry.

This feature also introduces the ability to associate a forwarding-class and optionally priority with IPv4 and IPv6 static routes. This is achieved by specifying the forwarding-class within the static-route-entry next-hop or indirect context.

Priority is optional when specifying the forwarding class of a static route, but once configured it can only be deleted and returned to unspecified by deleting the entire static route.

The following commands are enhanced to show the forwarding-class and priority associated with the displayed routes:

• show router route-table

• show router fib

• show router bgp routes

• show router rip database

• show router static-route

This feature uses a qos keyword to the show>router>route-table command. When this option is specified the output includes an additional line per route entry that displays the forwarding class and priority of the route. If a route has no fc and priority information, then the third line is blank. The following CLI shows an example:

show router route-table [family] [ip-prefix[/prefix-length]] [longer | exact] [protocol protocol-name] qos

An example output of this command is shown below:

A:Dut-A# show router route-table 10.1.5.0/24 qos
===============================================================================
Route Table (Router: Base)
===============================================================================
Dest Prefix                                   Type    Proto    Age         Pref
       Next Hop[Interface Name]                                     Metric
       QoS
-------------------------------------------------------------------------------
10.1.5.0/24                                   Remote  BGP      15h32m52s   0
       PE1_to_PE2                                                   0
       h1, high
-------------------------------------------------------------------------------
No. of Routes: 1
===============================================================================
A:Dut-A#

To enable QoS classification of ingress IP packets on an interface based on the QoS information associated with the routes that best match the packets the qos-route-lookup command is necessary in the configuration of the IP interface. The qos-route-lookup command has parameters to indicate whether the QoS result is based on lookup of the source or destination IP address in every packet. There are separate qos-route-lookup commands for the IPv4 and IPv6 packets on an interface, which allows QPPB to enabled for IPv4 only, IPv6 only, or both IPv4 and IPv6. Current QPPB based on a source IP address is not supported for IPv6 packets nor is it supported for ingress subscriber management traffic on a group interface.

The qos-route-lookup command is supported on the following types of IP interfaces:

• base router network interfaces (config>router>interface)

• VPRN SAP and spoke SDP interfaces (config>service>vprn>interface)

• VPRN group-interfaces (config>service>vprn>sub-if>grp-if)

• IES SAP and spoke SDP interfaces (config>service>ies>interface)

• IES group-interfaces (config>service>ies>sub-if>grp-if)

When the qos-route-lookup command with the destination parameter is applied to an IP interface and the destination address of an incoming IP packet matches a route with QoS information the packet is classified to the fc and priority associated with that route, overriding the fc and priority/profile determined from the SAP-Ingress or network qos policy associated with the IP interface. If the destination address of the incoming packet matches a route with no QoS information the fc and priority of the packet remain as determined by the SAP-Ingress or network qos policy.

Similarly, when the qos-route-lookup command with the source parameter is applied to an IP interface and the source address of an incoming IP packet matches a route with QoS information the packet is classified to the fc and priority associated with that route, overriding the fc and priority/profile determined from the SAP-Ingress or network qos policy associated with the IP interface. If the source address of the incoming packet matches a route with no QoS information the fc and priority of the packet remain as determined by the SAP-Ingress or network qos policy.

Currently, QPPB is not supported for ingress MPLS traffic on network interfaces or on CsC PE’-CE’ interfaces (config>service>vprn>nw-if).

In some circumstances (IP VPN inter-AS model C, Carrier Supporting Carrier, indirect static routes, and so on) an IPv4 or IPv6 packet may arrive on a QPPB-enabled interface and match a route A1 whose next-hop N1 is resolved by a route A2 with next-hop N2 and perhaps N2 is resolved by a route A3 with next-hop N3, and so on. The QPPB result is based only on the forwarding-class and priority of route A1. If A1 does not have a forwarding-class and priority association then the QoS classification is not based on QPPB, even if routes A2, A3, and so on have forwarding-class and priority associations.

When ECMP is enabled some routes may have multiple equal-cost next-hops in the forwarding table. When an IP packet matches such a route the next-hop selection is typically based on a hash algorithm that tries to load balance traffic across all the next-hops while keeping all packets of a specific flow on the same path. The QPPB configuration model described in Associating an FC and priority with a route allows different QoS information to be associated with the different ECMP next hops of a route. The forwarding-class and priority of a packet matching an ECMP route is based on the particular next-hop used to forward the packet.

When BGP FRR is enabled some BGP routes may have a backup next-hop in the forwarding table in addition to the one or more primary next-hops representing the equal-cost best paths allowed by the ECMP/multipath configuration. When an IP packet matches such a route a reachable primary next-hop is selected (based on the hash result) but if all the primary next-hops are unreachable then the backup next-hop is used. The QPPB configuration model described in Associating an FC and priority with a route allows the forwarding-class and priority associated with the backup path to be different from the QoS characteristics of the equal-cost best paths. The forwarding class and priority of a packet forwarded on the backup path is based on the fc and priority of the backup route.

When an IPv4 or IPv6 packet with destination address X arrives on an interface with both QPPB and policy-based-routing enabled:

• There is no QPPB classification if the IP filter action redirects the packet to a directly connected interface, even if X is matched by a route with a forwarding-class and priority

• QPPB classification is based on the forwarding-class and priority of the route matching IP address Y if the IP filter action redirects the packet to the indirect next-hop IP address Y, even if X is matched by a route with a forwarding-class and priority.

Source-address based QPPB is not supported on any SAP or spoke SDP interface of a VPRN configured with the grt-lookup command.

When QPPB is enabled on a SAP IP interface the forwarding class of a packet may change from fc1, the original fc determined by the SAP ingress QoS policy to fc2, the new fc determined by QPPB. In the ingress datapath SAP ingress QoS policies are applied in the first P chip and route lookup/QPPB occurs in the second P chip. This has the implications listed below:

• Ingress remarking (based on profile state) is always based on the original fc (fc1) and sub-class (if defined).

• The profile state of a SAP ingress packet that matches a QPPB route depends on the configuration of fc2 only. If the de-1-out-profile flag is enabled in fc2 and fc2 is not mapped to a priority mode queue then the packet is marked out of profile if its DE bit = 1. If the profile state of fc2 is explicitly configured (in or out) and fc2 is not mapped to a priority mode queue, then the packet is assigned this profile state. In both cases there is no consideration of whether fc1 was mapped to a priority mode queue.

• The priority of a SAP ingress packet that matches a QPPB route depends on several factors. If the de-1-out-profile flag is enabled in fc2 and the DE bit is set in the packet then priority is low regardless of the QPPB priority or fc2 mapping to profile mode queue, priority mode queue or policer. If fc2 is associated with a profile mode queue then the packet priority is based on the explicitly configured profile state of fc2 (in profile = high, out profile = low, undefined = high), regardless of the QPPB priority or fc1 configuration. If fc2 is associated with a priority mode queue or policer then the packet priority is based on QPPB (unless DE=1), but if no priority information is associated with the route then the packet priority is based on the configuration of fc1 (if fc1 mapped to a priority mode queue then it is based on DSCP/IP prec/802.1p and if fc1 mapped to a profile mode queue then it is based on the profile state of fc1).

QPPB interactions with SAP ingress QoS summarizes these interactions.

This feature introduces a generic operational group object which associates different service endpoints (pseudowires and SAPs) located in the same or in different service instances. The operational group status is derived from the status of the individual components using specific rules specific to the application using the concept. A number of other service entities, the monitoring objects, can be configured to monitor the operational group status and to perform specific actions as a result of status transitions. For example, if the operational group goes down, the monitoring objects are brought down.

The following SAP encapsulations are supported on the 7750 SR and 7950 XRS VPRN service:

• Ethernet null

• Ethernet dot1q

• QinQ

• LAG

• Tunnel (IPsec or GRE)

Pseudowire SAPs are supported on VPRN interfaces for the 7750 SR in the same way as on IES interfaces.

DSCP NameDSCP ValueDSCP ValueDSCP ValueLabel
Decimal Hexadecimal Binary
=============================================================
Default 00x00 0b000000be
nc1 48 0x30 0b110000h1
nc2 56 0x38 0b111000nc
ef 46 0x2e 0b101110ef
af11100x0a0b001010assured
af12120x0c0b001100assured
af13140x0e0b001110assured
af21 18 0x12 0b010010l1
af22 20 0x14 0b010100l1
af23220x160b010110l1
af31 26 0x1a 0b011010l1
af32 28 0x1c 0b011100l1
af33 30 0x1d 0b011110l1
af41 34 0x22 0b100010h2
af42 36 0x24 0b100100h2
af43 38 0x26 0b100110h2

default*0

*The default forwarding class mapping is used for all DSCP names or values for which there is no explicit forwarding class mapping.

The 7750 SR and 7950 XRS support multiple mechanisms to provide transport tunnels for the forwarding of traffic between PE routers within the 2547bis network.

The 7750 SR and 7950 XRS VPRN implementation supports the use of:

• RSVP-TE protocol to create tunnel LSPs between PE routers

• LDP protocol to create tunnel LSP's between PE routers

• GRE tunnels between PE routers

These transport tunnel mechanisms provide the flexibility of using dynamically created LSPs where the service tunnels are automatically bound (the autobind feature) and the ability to provide specific VPN services with their own transport tunnels by explicitly binding SDPs if needed. When the autobind is used, all services traverse the same LSPs and do not allow alternate tunneling mechanisms (like GRE) or the ability to craft sets of LSPs with bandwidth reservations for specific customers as is available with explicit SDPs for the service.

The 7750 SR and 7950 XRS allow setting the maximum number of routes that can be accepted in the VRF for a VPRN service. There are options to specify a percentage threshold at which to generate an event that the VRF table is near full and an option to disable additional route learning when full or only generate an event.

T-LDP status signaling and PW active/standby signaling capabilities are supported on Ipipe and Epipe spoke SDPs.

Spoke SDP termination on an IES or VPRN provides the ability to cross-connect traffic entering on a spoke SDP, used for Layer 2 services (VLLs or VPLS), on to an IES or VPRN service. From a logical point of view the spoke SDP entering on a network port is cross-connected to the Layer 3 service as if it had entered using a service SAP. The main exception to this is traffic entering the Layer 3 service using a spoke SDP is handled with network QoS policies instead of access QoS policies.

When a SAP down or SDP binding down status message is received by the PE in which the Ipipe or Ethernet Spoke-SDP is terminated on an IES or VPRN interface, the interface is brought down and all associated routes are withdrawn in a similar way when the Spoke-SDP goes down locally. The same actions are taken when the standby T-LDP status message is received by the IES/VPRN PE.

This feature can be used to provide redundant connectivity to a VPRN or IES from a PE providing a VLL service, as shown in Active/standby VRF using resilient Layer 2 circuits.

This feature can be used to provide redundant connectivity to a VPRN or IES from a PE providing a VLL service, as shown in Active/standby VRF using resilient Layer 2 circuits, using either Epipe or Ipipe spoke-SDPs. This feature is supported on the 7450 ESS and 7750 SR only.

In Active/standby VRF using resilient Layer 2 circuits, PE1 terminates two spoke SDPs that are bound to one SAP connected to CE1. PE1 chooses to forward traffic on one of the spoke SDPs (the active spoke-SDP), while blocking traffic on the other spoke SDP (the standby spoke SDP) in the transmit direction. PE2 and PE3 take any spoke SDPs for which PW forwarding standby has been signaled by PE1 to an operationally down state.

The 7450 ESS, 7750 SR, and 7950 XRS routers are expected to fulfill both functions (VLL and VPRN/IES PE), while the 7705 SAR must be able to fulfill the VLL PE function. Spoke SDP redundancy model illustrates the model for spoke SDP redundancy into a VPRN or IES.

ECMP and weighted ECMP into RSVP-TE and SR-TE LSPs is supported for Ipipe and Epipe spoke SDPs terminating on IP interfaces in an IES or VPRN, or for spoke SDP termination on a routed VPLS. It is also supported for SDPs using LDP over RSVP tunnels. Weighted ECMP is configured under the SDP used by the service, as follows:

config
   service
      sdp <sdp-id>
         [no] weighted-ecmp

Default: no weighted-ecmp

When a service uses a provisioned SDP on which weighted ECMP is configured, a path is selected based on the configured hash. Paths are then load balanced across LSPs used by an SDP according to normalized LSP load balancing weights. If one or more LSPs in the ECMP set to a specific next hop has no load-balancing-weight value configured, then regular ECMP spraying is used.

Using OSPF as a CE to PE routing protocol allows OSPF that is currently running as the IGP routing protocol to migrate to an IP-VPN backbone without changing the IGP routing protocol, introducing BGP as the CE-PE or relying on static routes for the distribution of routes into the service providers IP-VPN. The following features are supported:

• Advertisement/redistribution of BGP-VPN routes as summary (type 3) LSAs flooded to CE neighbors of the VPRN OSPF instance. This occurs if the OSPF route type (in the OSPF route type BGP extended community attribute carried with the VPN route) is not external (or NSSA) and the locally configured domain-id matches the domain-id carried in the OSPF domain ID BGP extended community attribute carried with the VPN route.

• OSPF sham links; a sham link is a logical PE-to-PE unnumbered point-to-point interface that essentially rides over the PE-to-PE transport tunnel. A sham link can be associated with any area and can therefore appear as an intra-area link to CE routers attached to different PEs in the VPN.

To use this feature, network IP interfaces that can have the feature enabled must first be identified. Participating interfaces are identified as having the untrusted state. The router supports a maximum of 15 network interfaces that can participate in this feature.

The following command is used to enable or disable this feature.

config>router>interface>untrusted [default-forwarding {forward | drop}]

Normally, the user applies the untrusted command to an inter-AS interface and PIP keeps track of the untrusted status of each interface. In the data path, an inter-AS interface that is flagged by PIP causes the default forwarding to be set to the value of the default-forwarding keyword (forward or drop).

For backward compatibility, default-forwarding on the interface is set to the forward value. This means that labeled packets are checked in the normal way against the table of programmed ILMs to decide if it should be dropped or forwarded in a GRT, a VRF, or a Layer 2 service context.

If the user sets the default-forwarding argument to the drop value, all labeled packets received on that interface are dropped. For details, see Data path forwarding behavior.

This feature sets the default behavior for an untrusted interface in the data path and for all ILMs. To allow the data path to provide an exception to the normal way of forwarding handling away from the default for VPRN ILMs, BGP must flag those ILMs to the data path.

The user enables exceptional ILM forwarding behavior, on a per-VPN-family basis, by using the following command:

configure>router>bgp>neighbor-trust [vpn-ipv4] [vpn-ipv6]

At a high level, BGP tracks each direct EBGP neighbor over an untrusted interface and to which it sent a VPRN prefix label. For each of those VPRN prefixes, BGP programs a bit map in the ILM that indicates, on a per-untrusted interface basis, whether the matching packets must be forwarded or dropped. For details, see CPM behavior.

This feature affects PIP behavior for management of network IP interfaces and in BGP for the resolution of BGP VPN-IPv4 and VPN-IPv6 prefixes.

The following are characteristics of CPM behavior related to PIP and the VPRN label security at inter-AS boundary feature:

• PIP manages the status of an untrusted interface based on the user configuration on the interface, as described in Feature configuration. It programs the interface record in the data path using a 4-bit untrusted interface identification number. A trusted interface has no untrusted record.

• BGP determines the status of trusted or untrusted of an EBGP neighbor by checking the untrusted record provided by PIP for the index of the interface used by the EBGP session to the neighbor.

• BGP only tracks the status of trusted or untrusted for directly connected EBGP neighbors. The neighbor address and the local address must be on the same local subnet.

• BGP includes the neighbor status of trusted or untrusted in the tribe criteria. For example, if a group consists of two untrusted EBGP neighbors and one trusted EBGP neighbor and all three neighbors have the same local-AS, neighbor-AS, and export policy, then the result is two different tribes.

  As a result, if the interface status changes from trusted to untrusted or untrusted to trusted, the EBGP neighbors on that interface bounce.

• When the feature is enabled for a specified VPN family and BGP advertises a label for one or more resolved VPN prefixes to a group of trusted and untrusted EBGP neighbors, it creates a 16-bit map in the ILM record in which it sets the bit position corresponding to the identification number of each untrusted interface used by a EBGP session to a neighbor to which it sent the label.

  A bit in the ILM record bit-map is referred to as the untrusted interface forwarding bit. The bit position corresponding to the identification number of any other untrusted interface is left clear.

  For details on the data path of the ILM bit-map record, see Data path forwarding behavior.

• Because the same label value is advertised for prefixes in the same VRF (label per-VRF mode) and for prefixes with the same next hop (label per-next-hop mode), BGP programs the forwarding bit position in the ILM bit map for both VPN IPv4 and VPN IPv6 prefixes sharing the same label, as long as the feature is enabled for at least one of the two VPN families.

• BGP tracks, on a per-untrusted interface basis, the number of RIB-Out entries to EBGP neighbors that reference a specific VPN label. When that reference transitions from zero to a positive value or from a positive value to zero, the label for the ILM of the VPN prefix is re-downloaded to the IOM with the forwarding bit position in the ILM bit map record updated accordingly (set or unset, respectively).

This feature supports label per-VRF and label per-next-hop modes for the PE role. The feature supports label per-next-hop mode for the ASBR role.

The feature is not supported with label per-prefix mode in a PE role and is not supported in a Carrier Supporting Carrier (CSC) PE role.

ILM forwarding on a trusted interface behaves as in prior releases and is not changed. The ILM forwarding bit map is ignored and packets are forwarded normally.

ILM forwarding on an untrusted interface follows these rules:

• Only the top-most label in the label stack in a received packet is checked against the next set of rules. The top label can correspond to any one of the following applications:

  • a transport label with a pop or swap operation of static, RSVP-TE, SR-TE, LDP, SR-ISIS, SR-OSPF, or BGP-LU

  • a BGP VPRN inter-AS option B label with a swap operation when the router acts in the ASBR role for VPN routes

  • a service delimiting label for a local VRF when the router acts as a PE in a VPRN service

• The data path checks the bit position in the bit map in the ILM record, when present, that corresponds to the untrusted interface identification number in the interface record and then makes a forwarding decision to drop or forward.

  A decision to forward means that a labeled packet proceeds to the regular ILM processing and its label stack is checked against the table of programmed ILMs to decide if the packet should be:

  • dropped

  • forwarded to CPM

  • forwarded as an MPLS packet

  • forwarded as an IP packet in a GRT or a VRF context

  • forwarded as a packet in a Layer 2 service context

• The following are the processing rules of the ILM:

  • interface default-forwarding=forward and ILM bit-map not present ⇒ forward packet

  • interface default-forwarding=forward and interface forwarding bit position in the ILM bit-map 1 ⇒ forward packet

  • interface default-forwarding=forward and interface forwarding bit position in the ILM bit-map zero ⇒ drop packet

  • interface default-forwarding=drop and ILM bit-map not present ⇒ drop packet

  • interface default-forwarding=drop and interface forwarding bit position in the ILM bit-map zero ⇒ drop packet

  • interface default-forwarding=drop and interface forwarding bit position in the ILM bit-map 1 ⇒ forward packet

• When the EBGP neighbor is not directly connected, BGP does not track that neighbor (see CPM behavior). In this case, the VPRN packet is received with a transport label or without a transport label if implicit-null is enabled in LDP or RSVP-TE for the transport label. Either way, the forwarding decision for the packet is solely dictated by the configuration of the default-forwarding value on the incoming interface.

• If the direct EBGP neighbor sends a VPRN packet using the MPLS-over-GRE encapsulation, the data path does not check the interface forwarding bit position in the ILM bit map. In this case, the forwarding decision of the packet is solely dictated by the configuration of the default-forwarding value on the incoming interface.

  SR OS EBGP neighbors never use the MPLS-over-GRE encapsulation over an inter-AS link, but third party implementations may do this.

CE

customer premises equipment dedicated to one particular business/enterprise

PE

service provider router that connects to a CE to provide a business VPN service to the associated business/enterprise

CSC-CE

an ASBR/peering router that is connected to the CSC-PE of another service provider for purposes of using the associated CsC IP VPN service for backbone transport

CSC-PE

a PE router belonging to the backbone service provider that supports one or more CSC IP VPN services

A PE router deployed by a customer service provider to provide Internet access, IP VPNs, or L2 VPNs may connect directly to a CSC-PE device, or it may back haul traffic within its local ‟site” to the CSC-CE that provides this direct connection. Here, ‟site” means a set of routers owned and managed by the customer service provider that can exchange traffic through means other than the CSC service. The function of the CSC service is to provide IP/MPLS reachability between isolated sites.

The CSC-CE is a ‟CE” from the perspective of the backbone service provider. There may be multiple CSC-CEs at a specific customer service provider site and each one may connect to multiple CSC-PE devices for resiliency/multi-homing purposes.

The CSC-PE is owned and managed by the backbone service provider and provides CSC IP VPN service to connected CSC-CE devices. In many cases, the CSC-PE also supports other services, including regular business IP VPN services. A single CSC-PE may support multiple CSC IP VPN services. Each customer service provider is allocated its own VRF within the CSC-PE; VRFs maintain routing and forwarding separation and allow the use of overlapping IP addresses by different customer service providers.

A backbone service provider may not have the geographic span to connect, with reasonable cost, to every site of a customer service provider. In this case, multiple backbone service providers may coordinate to provide an inter-AS CSC service. Different inter-AS connectivity options are possible, depending on the trust relationships between the different backbone service providers.

The CSC Connectivity Models apply to the 7750 SR and 7950 XRS only.

This section applies to CSC-PE1, CSC-PE2 and CSC-PE3 in Carrier Supporting Carrier reference diagram.

This section applies only to the 7750 SR.

From the point of view of the CSC-PE, the IP/MPLS interface between the CSC-PE and a CSC-CE has these characteristics:

1. The CSC interface is associated with one (and only one) VPRN service. Routes with the CSC interface as next-hop are installed only in the routing table of the associated VPRN.

2. The CSC interface supports EBGP or IBGP for exchanging labeled IPv4 routes (RFC 8277). The BGP session may be established between the interface addresses of the two routers or else between a loopback address of the CSC-PE VRF and a loopback address of the CSC-CE. In the latter case, the BGP next-hop is resolved by either a static or OSPFv2 route.

3. An MPLS packet received on a CSC interface is dropped if the top-most label was not advertised over a BGP (RFC 8277) session associated with one of the VPRN’s CSC interfaces.

4. The CSC interface supports ingress QoS classification based on 802.1p or MPLS EXP. It is possible to configure a default FC and default profile for the CSC interface.

5. The CSC interface supports QoS (re)marking for egress traffic. Policies to remark 802.1p or MPLS EXP based on forwarding-class and profile are configurable per CSC interface.

6. By associating a port-based egress queue group instance with a CSC interface, the egress traffic can be scheduled/shaped with per-interface, per-forwarding-class granularity.

7. By associating a forwarding-plane based ingress queue group instance with a CSC interface, the ingress traffic can be policed to per-interface, per-forwarding-class granularity.

8. Ingress and egress statistics and accounting are available per CSC interface. The exact set of collected statistics depends on whether a queue-group is associated with the CSC interface, the traffic direction (ingress vs. egress), and the stats mode of the queue-group policers.

An Ethernet port or LAG with a CSC interface can be configured in hybrid mode or network mode. The port or LAG supports null, dot1q or qinq encapsulation. To create a CSC interface on a port or LAG in null mode, the following commands are used:

config>service>vprn>nw-if>port port-id config>service>vprn>nw-if>lag lag-id

To create a CSC interface on a port or LAG in dot1q mode, the following commands are used:

config>service>vprn>nw-if>port port-id:qtag1 config>service>vprn>nw-if>lag port-id:qtag1

To create a CSC interface on a port or LAG in qinq mode, the following commands are used:

config>service>vprn>nw-if>port port-id:qtag1.qtag2 config>service>vprn>nw-if>port port-id:qtag1.* config>service>vprn>nw-if>lag port-id:qtag1.qtag2 config>service>vprn>nw-if>lag port-id:qtag1.*

A CSC interface supports the same capabilities (and supports the same commands) as a base router network interface, except it does not support:

• IPv6

• LDP

• RSVP

• Proxy ARP (local/remote)

• Network domain configuration

• DHCP

• Ethernet CFM

• Unnumbered interfaces

BGP-8277 is used as the label distribution protocol on the CSC interface. When BGP in a CSC VPRN needs to distribute a label corresponding to a received VPN-IPv4 route, it takes the label from the global label space. The allocated label is not re-used for any other FEC regardless of the routing instance (base router or VPRN). If a label L is advertised to the BGP peers of CSC VPRN A then a received packet with label L as the top most label is only valid if received on an interface of VPRN A, otherwise the packet is discarded.

To use BGP-8277 as the label distribution protocol on the CSC interface, add the family label-ipv4 command to the family configuration at the instance, group, or neighbor level. This causes the capability to send and receive labeled-IPv4 routes {AFI=1, SAFI=4} to be negotiated with the CSC-CE peers.

To configure a VPRN to support CSC service, the carrier-carrier-vpn command must be enabled. The command fails if the VPRN service has any existing SAP or spoke SDP interfaces. A CSC interface can be added to a VPRN (using the network-interface command) only if the carrier-carrier-vpn command is enabled.

A VPRN service with the carrier-carrier-vpn command may be provisioned to use auto-bind-tunnel, configured spoke SDPs, or some combination. All SDP types are supported except for:

• GRE SDPs
• LDP over RSVP-TE tunnel SDPs

Other aspects of VPRN configuration are the same in a CSC model as in a non-CSC model.

VPRN management can be enabled by configuring the appropriate management protocol within the VPRN from the vprn>management context. The following protocols can be enabled in this context:

• FTP

• gRPC

• NETCONF

• SSH

• Telnet

• Telnetv6

SNMP access is not controlled in the vprn>management context. See section SNMP management.

NTP and PTP access are not controlled in the vprn>management context. See NTP within a VPRN service and PTP within a VPRN service.

By default, all protocols are disabled. When one of these protocols is enabled, that VRF becomes a management VRF.

All other gRPC configurations remain global under the config>system>grpc context.

All other NETCONF configurations remain global under the config>system>management-interface>netconf context.

The TLS profiles needed for gRPC can be configured under the config>system>security>tls context.

To configure the system local user profile configuration for local user authentication and authorization, including VPRNs, use the following CLI contexts:

• Classic CLI

  config>system>security>profile

• MD-CLI

  configure system security aaa local-profiles profile

To configure AAA servers, use the following CLI contexts:

• Classic CLI

  config>system>security for system AAA servers

  config>service>vprn>aaa>remote-servers for AAA remote servers under the VPRN

• MD-CLI

  configure system security aaa for system AAA servers

  configure service vprn aaa remote-servers for AAA remote servers under the VPRN

When AAA servers are configured using the preceding commands, they are used as follows:

• If servers are configured under the VPRN AAA, only the VPRN AAA servers are used.

  For example, the authentication-order command lists the order as local, TACACS+, and RADIUS, while the VPRN only has a RADIUS server configured, and under the system AAA servers both TACACS+ and RADIUS are configured. In this case, if a management session connects to the VPRN and the destination IP matches a local interface in the VPRN, the SR OS tries the local AAA first, and then RADIUS as configured in the VPRN. The SR OS does not try the system AAA servers because there is a AAA server configured in the VPRN.

• If servers are configured under VPRN AAA and the VPRN AAA parameters are configured for in-band, out-of-band, or VPRN, the servers can be used for the VPRN and the system.

• If no AAA servers are configured under VPRN AAA, the system AAA servers are used.

The SR OS SNMP agent can be reached via a VPRN interface address when configure>service>vprn>snmp>access is enabled.

Using an SNMP community defined inside the VPRN context (configure>service>vprn>snmp>community) or a user associated with an SNMPv3 USM access group defined in the system context (configure>system>snmp>access) allows access to a subset of the full SNMP data model. This subset can be seen in the output of show system security view "vprn-view".

Using an SNMP community defined in the system context (configure>system> security>snmp>community) allows access to the full SNMP data model (unless otherwise restricted used SNMP views).

Alternatively, grt leaking and a Base routing IP address can be used (along with an SNMP community defined at the system context) to get access to the entire SNMP data model (see the allow-local-management command).

A network manager using SNMP, cannot discover or fully manage an SR OS router using an SNMP community defined inside the VPRN context. Full SNMP access requires using one of the approaches described above.

SNMP communities configured under a VPRN are associated with the SNMP context "vprn". For example, walking the ifTable (IF-MIB) using the community configured for VPRN 5 returns counters and status for interfaces in VPRN 5 only.

Syslog, SNMP traps and Netconf notifications are generated via the Event Logging System.

VPRN syslog destinations are defined under the config>service>vprn>log>syslog context.

SNMP trap destination in a VPRN are defined using the config>service>vprn>log>snmp-trap-group context.

Events for the whole system can be directed to a destination within the management VPRN by using the config>log>services-all-events command. See the 7450 ESS, 7750 SR, 7950 XRS, and VSR System Management Guide for details of this command.

DNS default domain name and DNS servers for domain name resolution can be defined within a VPRN in the config>service>vprn>dns context.

In addition to node management using the IP addresses of VPRN interfaces, see Node management using VPRN, management via a VPRN can also be achieved using IP addresses in the Base routing instance and GRT leaking.

When a management packet arrives on a VPRN, there is a lookup for the destination IP address of the packet. If the destination IP is resolved using VPRN and the corresponding protocol is enabled under VPRN management, then the packet is extracted to CPM.

If the destination IP address is not a VRF IP and GRT leaking is enabled, a second lookup is done in the GRT FIB. If the IP belongs to a local interface in GRT and allow-local-management is enabled under enable-grt, then the packet is extracted using GRT leaking to the CPM.

To change the service label mode of the VPRN for the 7750 SR, the config>service>vprn>label-mode {vrf | next-hop} command is used:

The default mode (if the command is not present in the VPRN configuration) is vrf meaning distribution of one service label for all routes of the VPRN. When a VPRN X is configured with the label-mode next-hop command the service label that it distributes with an IPv4 or IPv6 route that it exports depends on the type of route as summarized in Service labels distributed in service label per next hop mode.

A change to the label-mode of a VPRN requires the VPRN to first be shutdown.

The service label per next-hop mode has the following restrictions (applies only to the 7750 SR):

• ECMP

  The VPRN label mode should be set to VRF if distribution of traffic across the multiple PE-CE next-hop interfaces of an ECMP route is needed.

• hub and spoke VPN

  The VPRN label mode should not be set to next-hop if the operator does not want the hub-connected CE to be involved in the forwarding of spoke-to-spoke traffic.

• BGP next-hop indirection

  BGP next-hop indirection has no benefit in service label per next-hop mode. When the resolved next-hop interface of a BGP next-hop changes all of the affected BGP routes must be re-advertised to VPRN peers with the new service label corresponding to the new resolved next-hop.

• BGP anycast

  When a PE failure results in redirection of MPLS packets to the other PE in a dual-homed pair, the service label mode is forced to VRF, for example, FIB lookup determines the next-hop even if the label mode of the VPRN is configured as next-hop.

• U-turn routing

  U-turn routing is effectively disabled by service-label per next-hop.

• Carrier Supporting Carrier

  The label-mode configuration of a VPRN with CSC interfaces is ignored for BGP-8277 routes learned from connected CSC-CE devices.

To configure this feature:

• Enable resolution to RSVP-TE or SR-TE tunnels in the auto-bind-tunnel context.

• Enable ECMP in the auto-bind-tunnel context.

• Enable class-forwarding in the vprn context.

• Define at least one class forwarding policy in the mpls context, the FC to sets associations and the LSP to (policy, set) associations.

The SR OS CBF implementation supports spraying of packets over a maximum of six forwarding sets of ECMP LSPs only when the system profile is profile-b that is supported on an FP4 or later-based CPM. In any other case, the maximum number of forwarding sets of ECMP LSPs is four.

config
      router
            [no] mpls
                  class-forwarding-policy policy-name create
                  fc be forwarding-set set-id <1..6>
                  fc l2 forwarding-set set-id <1..6>
                  fc af forwarding-set set-id <1..6>
                  fc l1 forwarding-set set-id <1..6>
                  fc h2 forwarding-set set-id <1..6>
                  fc ef forwarding-set set-id <1..6>
                  fc h1 forwarding-set set-id <1..6>
                  fc nc forwarding-set set-id <1..6>
                  [no] default-set set-id <1..6>

All FCs are mapped to set 1 as soon as the policy is created. The user can make changes to the mapping of FCs as required. An FC that is not added to the class-forwarding policy, is always mapped to set 1. At most, an FC can be mapped to a single forwarding set. One or more FCs can be mapped to the same set. The user can indicate the initial default set by including the default-set option.

The default forwarding set is used to forward packets of any FC in cases where all LSPs of the forwarding set the FC maps to become operationally DOWN. The router uses the user-configured default set as the initial default set. Otherwise, the router selects the lowest numbered set as the default forwarding set in a class-forwarding policy. When the last LSP in a default forwarding set goes into an operationally DOWN state, the router designates the next lowest-numbered set as the new default forwarding set.

A mapping to a class-forwarding policy and set is added to the existing CBF configuration of an RSVP-TE or SR-TE LSP or to an LSP template. The following commands perform this function:

config>router>mpls>lsp>class-forwarding forward-set policy policy-name set set-id

config>router>mpls>lsp-template>class-forwarding forwarding-set policy policy-name set set-id

An MPLS LSP only maps to a single class-forwarding policy and forwarding set. Multiple LSPs can map to the same policy and set. If they form an ECMP set, from the IGP shortcut perspective, packets of the FCs mapped to this set are sprayed over these LSPs based on a modulo operation of the output of the hash routine on the headers of the packet and the number of LSPs in the set.

When a VPN-v4/v6 prefix is resolved, the default behavior of the data path is to spray the packets over the entire ECMP set using a modulo operation of the number of resolved next hops in the ECMP set and the output of the hash on the packet header fields. With class-based forwarding enabled, the FC of the packet, is used to look up the forwarding set ID. Then, a modulo operation is performed on the tunnel next hops of this set ID only, to spray packets of this FC. The data path concurrently implements ECMP within the tunnels of each set ID.

The CBF information of the LSPs forming the ECMP set is checked for consistency before programming. If more than a single class-forwarding policy exists, the set is considered inconsistent from a CBF perspective and no CBF information is programmed in the data-path and regular ECMP occurs.

Also, regardless of the CBF consistency check, the system programs the data-path with the full ECMP set.

The following describes the fall-back behavior in data path of the CBF feature.

An FC, for which all LSPs in the forwarding set are operationally DOWN, has its packets forwarded over the default forwarding set. The default forwarding set is either the initial default forwarding set configured by the user or the lowest numbered set in the class-forwarding policy that has one or more LSPs in the operationally UP state. If the initial or subsequently elected default forwarding set has all its LSPs operationally DOWN, the next lower numbered forwarding set, which has at least one LSP in the operationally UP state, is elected as the default forwarding set.

If all LSPs of all forwarding sets become operationally DOWN, the router resumes regular ECMP spraying on the remaining LSPs in the full ECMP set.

Whenever the first LSP in a forwarding set becomes operationally UP, the router triggers the re-election of the default set and selects this set as the new default set, if it is the initial default set, otherwise, it selects the lowest numbered set.

SR OS implements a hierarchical ECMP architecture for BGP prefixes. The first level is the ECMP at the VPRN Level between different BGP next hop, and the second level is ECMP at the auto-bind-tunnel level, having the same next hop. This CBF feature is applied at the auto-bind-tunnel level. Weighted ECMP and the CBF feature are mutually exclusive on a per-BGP next-hop basis. When both are configured, Weighted ECMP takes the preference. CPM-originated packets on the router, including control plane and OAM packets, are forwarded over a single LSP from the set of LSPs that the packet's FC is mapped to, as per the CBF configuration.

BGP C-multicast signaling must be enabled for an MVPN instance to use P2MP RSVP-TE or LDP as I-PMSI (equivalent to ‛Default MDT’, as defined in draft Rosen MVPN) and S-PMSI (equivalent to ‛Data MDT’, as defined in draft Rosen MVPN).

By default, all PE nodes participating in an MVPN receive data traffic over I-PMSI. Optionally, (C-*, C-*) wildcard S-PMSI can be used instead of I-PMSI. See section Wildcard (C-*, C-*) P2MP LSP S-PMSI for more information. For efficient data traffic distribution, one or more S-PMSIs can be used, in addition to the default PMSI, to send traffic to PE nodes that have at least one active receiver connected to them. For more information, see P2MP LSP S-PMSI.

Only one unique multicast flow is supported over each P2MP RSVP-TE or P2MP LDP LSP S-PMSI. Number of S-PMSI that can be initiated per MVPN instance is restricted by CLI command maximum-p2mp-spmsi. P2MP LSP S-PMSI cannot be used for more than one (S,G) stream (that is, multiple multicast flow) as number of S-PMSI per MVPN limit is reached. Multicast flows that cannot switch to S-PMSI remain on I-PMSI.

Point-to-Multipoint RSVP-TE LSP as inclusive or selective provider tunnel is available with BGP NG-MVPN only. P2MP RSVP-TE LSP is dynamically setup from root node on auto discovery of leaf PE nodes that are participating in multicast VPN. Each RSVP-TE I-PMSI or S-PMSI LSP can be used with a single MVPN instance only.

RSVP-TE LSP template must be defined (see 7450 ESS, 7750 SR, 7950 XRS, and VSR MPLS Guide) and bound to MVPN as inclusive or selective (S-PMSI is for efficient data distribution and is optional) provider tunnel to dynamically initiate P2MP LSP to the leaf PE nodes learned via NG-MVPN auto-discovery signaling. Each P2MP LSP S2L is signaled based on parameters defined in LSP template.

Point-to-Multipoint LDP LSP as inclusive or selective provider tunnel is available with BGP NG-MVPN only. P2MP LDP LSP is dynamically setup from leaf nodes on auto discovery of leaf node PE nodes that are participating in multicast VPN. Each LDP I-PMSI or S-PMSI LSP can be used with a single MVPN instance only.

The multicast-traffic CLI command must be configured per LDP interface to enable P2MP LDP setup. P2MP LDP must also be configured as inclusive or selective (S-PMSI is for efficient data distribution and is optional) provider tunnel per MVPN to dynamically initiate P2MP LSP to leaf PE nodes learned via NG-MVPN auto-discovery signaling.

Wildcard S-PMSI allows usage of selective tunnel as a default tunnel for a specific MVPN. By using wildcard S-PMSI, operators can avoid full mesh of LSPs between MVPN PEs, reducing related signaling, state, and BW consumption for multicast distribution (no traffic is sent to PEs without any receivers active on the default PMSI).

The SR OS allows an operator to configure wildcard S-PMSI for ng-MVPN (config>service>vprn>mvpn>pt>inclusive>wildcard-spmsi), using LDP and RSVP-TE in P-instance. Support includes:

• IPv4 and IPv6

• PIM ASM and SSM

• directly attached receivers

The SR OS (C-*, C-*) wildcard implementation uses wildcard S-PMSI instead of I-PMSI for a specific MVPN. To switch MVPN from I-PMSI to (C-*, C-*) S-PMSI a VPRN shutdown is required. ISSU and Upstream Multicast Hop (UMH) redundancy can be used to minimize the impact.

To minimize outage, the following upgrade order is recommended:

1. Route Reflector

2. Receiver PEs

3. backup UMH

4. active UMH

RSVP-TE/mLDP configuration under inclusive provider tunnel (config>service>vprn>mvpn>pt>inclusive) apply to wildcard S-PMSI when enabled.

Wildcard C-S and C-G values are encoded as defined in RFC6625: using zero for Multicast Source Length and Multicast Group Length and omitting Multicast Source and Multicast Group values respectively in MCAST_VPN_NLRI. For example, a (C-*, C-*) is advertised as: RD, 0x00, 0x00, and originating router's IP address.

The procedures implemented by SR OS are compliant to section 3 and 4 of RFC, 6625. Wildcards encoded as described above are carried in NLRI field of MP_REACH_NLRF_ATTRIBUTE. Both IPv4 and IPv6 are supported: (AFI) of 1 or 2 and a Subsequent AFI (SAFI) of MCAST-VPN.

The (C-*, C-*) S-PMSI is established as follows:

• UMH PEs advertise I-PMSI A-D routes without tunnel information present (empty PTA) - encoded as per RFC6513/6514 before advertising wildcard S-PMSI. I-PMSI needs to be signaled and installed on receiver PEs, because (C-*, C-*) S-PMSI is only installed when a first receiver is added. However, no LSP is established for I-PMSI).

• UMH PEs advertise S-PMSI A-D route whose NLRI contains (C-*, C-*) with tunnel information encoded as per RFC 6625.

• Receiver PEs join wildcard S-PMSI if there are any receivers present.

To ensure correct operation of BSR between PEs with (C-*, C-*) S-PMSI signaling, SR OS implements two modes of operations for BSR.

By default (bsr unicast):

• BSR PDUs are sent/forwarded as unicast PDUs to neighbor PEs when I-PMSI with Pseudo-tunnel interface is installed.

• At every BSR interval timer BSR Unicast PDU are sent to all I-PMSI interfaces when this is an elected BSR.

• BSMs received as multicast from C-instance interfaces are flooded as unicast in the P-instance.

• All PEs process BSR PDU's received on I-PMSI Pseudo-tunnel interface as unicast packets.

• BSR PDU's are not forwarded to PE's management control interface.

• BSR unicast PDU's use PE's System IP address as destination IP and sender PE's System address as Source IP.

• The BSR unicast functionality ensures that no special state needs to be created for BSR when (C-*, C-*) S-PMSI is enabled, which is beneficiary considering low volume of BSR traffic.

BSR S-PMSI mode can be enabled to allow interoperability with other vendors. In that mode full mesh S-PMSI is required and created between all PEs in MVPN to exchange BSR PDUs between all PEs in MVPN. To operate as expected, the BSR S-PMSI mode requires a selective P-tunnel configuration. For IPv6 support (including dual-stack) of BSR S-PMSI mode, the IPv6 default system interface address must be configured as a loopback interface address under the VPRN and VPRN PIM contexts. Changing BSR signaling requires a VPRN shutdown.

Other key feature interactions and restrictions for (C-*, C-*) include the following:

• Extranet is fully supported with wildcard S-PMSI trees.

• (C-S, C-G) S-PMSIs are supported when (C-*, C-*) S-PMSI is configured (including both BW and receiver PE driven thresholds).

• Geo-redundancy is supported (deploying with geo-redundancy eliminates traffic duplication when geo-redundant source has no active receivers at a cost of slightly increased outage upon a switch because wildcard S-PMSI may need to be re-establish).

• PIM in P-instance is not supported.

• SR OS implementation requires wildcard encoding as per RFC6625 and I-PMSI/S-PMSI signaling as defined above (I-PMSI signaled with empty PTA then S-PMSI signaled with P-tunnel PTA) for interoperability. Implementations that do not adhere to RFC6625 encoding, or signal both I-PMSI and S-PMSI with P-tunnel PTA do not inter-operate with SR OS implementation).

NG-MVPN support P2MP RSVP-TE and P2MP LDP LSPs as selective provider multicast service interface (S-PMSI). S-PMSI is used to avoid sending traffic to PEs that participate in multicast VPN, but do not have any receivers for a specific C-multicast flow. This allows more-BW efficient distribution of multicast traffic over the provider network, especially for high bandwidth multicast flows. S-PMSI is spawned dynamically based on configured triggers as described in S-PMSI trigger thresholds section.

In MVPN, the head-end PE firstly discovers all the leaf PEs via I-PMSI A-D routes. It then signals the P2MP LSP to all the leaf PEs using RSVP-TE. In the scenario of S-PMSI:

1. The head-end PE sends an S-PMSI A-D route for a specific C-flow with the Leaf Information Required bit set.

2. The PEs who are interested in the C-flow respond with Leaf A-D routes.

3. The head-end PE then signals the P2MP LSP to all the leaf PEs using RSVP-TE.

Also, because the receivers may come and go, the implementation supports dynamically adding and pruning leaf nodes to and from the P2MP LSP.

When the tunnel type in the PMSI attribute is set to RSVP-TE P2MP LSP, the tunnel identifier is <Extended Tunnel ID, Reserved, Tunnel ID, P2MP ID>, as carried in the RSVP-TE P2MP LSP SESSION Object.

The PE can also learn via an A-D route that it needs to receive traffic on a particular RSVP-TE P2MP LSP before the LSP is actually setup. In this case, the PE needs to wait until the LSP is operational before it can modify its forwarding tables as directed by the A-D route.

Because of the way that LDP normally works, mLDP P2MP LSPs are setup without solicitation from the leaf PEs toward the head-end PE. The leaf PE discovers the head-end PE via I-PMSI or S-PMSI A-D routes. The tunnel identifier carried in the PMSI attribute is used as the P2MP FEC element. The tunnel identifier consists of the head-end PE’s address, along with a Generic LSP identifier value. The Generic LSP identifier value is automatically generated by the head-end PE.

This feature provides a multicast signaling solution for IP-VPNs, allowing the connection of IP multicast sources and receivers in C-instances, which are running PIM multicast protocol using Rosen MVPN with BGP SAFI and P2MP mLDP in P-instance. The solution dynamically maps each PIM multicast flow to a P2MP LDP LSP on the source and receiver PEs.

The feature uses procedures defined in RFC 7246: Multipoint Label Distribution Protocol In-Band Signaling in Virtual Routing and Forwarding (VRF) Table Context. On the receiver PE, PIM signaling is dynamically mapped to the P2MP LDP tree setup. On the source PE, signaling is handed back from the P2MP mLDP to the PIM. Because of dynamic mapping of multicast IP flow to P2MP LSP, provisioning and maintenance overhead is eliminated as multicast distribution services are added and removed from the VRF. Per (C-S, C-G) IP multicast state is also removed from the network, because P2MP LSPs are used to transport multicast flows.

Dynamic mLDP signaling for IP multicast in VPRN illustrates dynamic mLDP signaling for IP multicast in VPRN.

As illustrated in Dynamic mLDP signaling for IP multicast in VPRN, P2MP LDP LSP signaling is initiated from the receiver PE that receives PIM JOIN from a downstream router (Router A). To enable dynamic multicast signaling, the p2mp-ldp-tree-join must be configured on PIM customer-facing interfaces for the specific VPRN of Router A. This enables handover of multicast tree signaling from the PIM to the P2MP LDP LSP. Being a leaf node of the P2MP LDP LSP, Router A selects the upstream-hop as the root node of P2MP LDP FEC, based on a routing table lookup. If an ECMP path is available for a specific route, then the number of trees are equally balanced toward multiple root nodes. The PIM joins are carried in the Transit Source PE (Router B), and multicast tree signaling is handed back to the PIM and propagated upstream as native-IP PIM JOIN toward C-instance multicast source.

The feature is supported with IPv4 and IPv6 PIM SSM and IPv4 mLDP. Directly connected IGMP/MLD receivers are also supported, with PIM enabled on outgoing interfaces and SSM mapping configured, if required.

The following are feature restrictions:

• Dynamic mLDP signaling in a VPRN instance and Rosen or NG-MVPN are mutually exclusive.

• A single instance of P2MP LDP LSP is supported between the receiver PE and Source PE per multicast flow; there is no stitching of dynamic trees.

• Extranet functionality is not supported.

• The router LSA link ID or the advertising router ID must be a routable IPv4 address (including IPv6 into IPv4 mLDP use cases).

• IPv6 PIM with dynamic IPv4 mLDP signaling is not supported with EBGP or IBGP with IPv6 next-hop.

• Inter-AS and IGP inter-area scenarios where the originating router is altered at the ASBR and ABR respectively, (therefore PIM has no way to create the LDP LSP toward the source), are not supported.

• When dynamic mLDP signaling is deployed, a change in Route Distinguisher (RD) on the Source PE is not acted upon for any (C-S, C-G)s until the receiver PEs learn about the new RD (via BGP) and send explicit delete and create with the new RD.

• Procedures of Section 2 of RFC 7246 for a case where UMH and the upstream PE do not have the same IP address are not supported.

In multicast MVPN, by default, if multiple PE nodes form a peering with a common MVPN instance then each PE node originates a multicast tree locally toward the remaining PE nodes that are member of this MVPN instance. This behavior creates a mesh of I-PMSI across all PE nodes in the MVPN. It is often a case, that a specific VPN has many sites that host multicast receivers, but only few sites that either host both receivers and sources or sources only.

MVPN Sender-only/Receiver-only allows optimization of control and data plane resources by preventing unnecessary I-PMSI mesh when a specific PE hosts multicast sources only or multicast receivers only for a specific MVPN.

For PE nodes that host only multicast sources for a specific VPN, operators can now block those PEs, through configuration, from joining I-PMSIs from other PEs in this MVPN. For PE nodes that host only multicast receivers for a specific VPN, operators can now block those PEs, through configuration, to set-up a local I-PMSI to other PEs in this MVPN.

MVPN Sender-only/Receiver-only is supported with ng-MVPN using IPv4 RSVP-TE or IPv4 LDP provider tunnels for both IPv4 and IPv6 customer multicast. MVPN sender-only/receiver-only example depicts 4-site MVPN with sender-only, receiver-only and sender-receiver (default) sites.

Extra attention needs to be paid to BSR/RP placement when Sender-only/Receiver-only is enabled. Source DR sends unicast encapsulated traffic toward RP, therefore, RP shall be at sender-receiver or sender-only site, so that *G traffic can be sent over the tunnel. BSR shall be deployed at the sender-receiver site. BSR can be at sender-only site if the RPs are at the same site. BSR needs to receive packets from other candidate-BSR and candidate-RPs and also needs to send BSM packets to everyone.

The mLDP and RSVP-TE S-PMSIs support two types of data thresholds: bandwidth-driven and receiver-PE-driven. The threshold evaluation and bandwidth driven threshold functionality are described in Use of data MDTs.

In addition to the bandwidth threshold functionality, an operator can enable receiver-PE-driven threshold behavior. Receiver PE thresholds ensure that S-PMSI is only created when BW savings in P-instance justify extra signaling required to establish a new S-PMSI. For example, the number of receiver PEs interested in a specific C-multicast flow is meaningfully smaller than the number of receiver PEs for default PMSI (I-PMSI or wildcard S-PMSI). To ensure that S-PMSI is not constantly created/deleted, two thresholds need to be specified: receiver PE add threshold and receiver PE delete threshold (expected to be significantly higher).

When a (C-S, C-G) crosses a data threshold to create S-PMSI, instead of regular S-PMSI signaling, sender PE originates S-PMSI explicit tracking procedures to detect how many receiver PEs are interested in a specific (C-S, C-G). When receiver PEs receive an explicit tracking request, each receiver PE responds, indicating whether there are multicast receivers present for that (C-S, C-G) on the specific PE (PE is interested in a specific (C-S, C-G)). If the geo-redundancy feature is enabled, receiver PEs do not respond to explicit tracking requests for suppressed sources and therefore only Receiver PEs with an active join are counted against the configured thresholds on Source PEs.

Upon regular sampling and check interval, if the previous check interval had a non-zero receiver PE count (one interval delay to not trigger S-PMSI prematurely) and current count of receiver PEs interested in the specific (C-S, C-G) is non-zero and is less than the configured receiver PE add threshold, Source PE sets up S-PMSI for this (C-S, C-G) following standard ng-MVPN procedures augmented with explicit tracking for S-PMSI being established.

Data threshold timer should be set to ensure enough time is given for explicit tracking to complete (for example, setting the timer to value that is too low may create S-PMSI prematurely).

Upon regular data-delay-interval expiry processing, when BW threshold validity is being checked, a current receiver PE count is also checked (for example, explicit tracking continues on the established S-PMSI). If BW threshold no longer applies or the receiver PEs exceed receiver PE delete threshold, the S-PMSI is torn down and (C-S, C-G) joins back the default PMSI.

Changing of thresholds (including enabling disabling the thresholds) is allowed in service. The configuration change is evaluated at the next periodic threshold evaluation.

The explicit tracking procedures follow RFC 6513/6514 with clarification and wildcard S-PMSI explicit tracking extensions as described in IETF Draft: draft-dolganow-l3vpn-expl-track-00.

The existing Rosen implementation is compatible to provide an easy migration path.

The following migration procedures are supported:

• Upgrade all the PE nodes that need to support MVPN to the newer release.

• The old configuration is converted automatically to the new style.

• Node by node, MCAST-VPN address-family for BGP is enabled. Enable auto-discovery using BGP.

• Change PE-to-PE signaling to BGP.

SR OS creates a single Selective P-Multicast Service Interface (S-PMSI) per multicast stream: (S,G) or (*,G). To better manage bandwidth allocation in the network, multiple multicast streams are often bundled starting from the same root node into a single, multi-stream S-PMSI. Network bandwidth is usually managed per package or group of packages, instead of per channel.

Multi-stream S-PMSI supports a single S-PMSI for one or more IPv4 (C-S, C-G) or IPv6 (C-S, C-G) streams. Multiple multicast streams starting from the same VPRN going to the same set of leafs can use a single S-PMSI. Multi-stream S-PMSIs can:

• carry exclusively IPv4 or exclusively IPv6, or a mix of channels

• coexist with a single group S-PMSI

To create a multi-stream S-PMSI, an S-PMSI policy needs to be configured in the VPN context on the source node. This policy maps multiple (C-S, C-G) streams to a single S-PMSI. Because this configuration is done per MVPN, multiple VPNs can have identical policies, each configured for its own VPN context.

When mapping a multicast stream to a multi-stream S-PMSI policy, the data traverses the S-PMSI without first using the I-PMSI. (Before this feature, when a multicast stream was sourced, the data used the I-PMSI first until a configured threshold was met. After this, if the multicast data exceeded the threshold, it would signal the S-PMSI tunnel and switch from I-PMSI to S-PMSI.)

For multi-stream S-PMSI, if the policy is configured and the multicast data matches the policy rules, the multi-stream S-PMSI is used from the start without using the default I-PMSI.

Multiple multi-stream S-PMSI policies could be assigned to a specific S-PMSI configuration. In this case, the policy acts as a link list. The first (lowest index) that matches the multi-stream S-PMSI policy is used for that specific stream.

The rules for matching a multi-stream S-PMSI on the source node are listed here.

S-PMSI to (C-S, C-G) mapping on Source-PE, in sequence:

1. The multi-stream S-PMSI policy is evaluated, starting from the lowest numerical policy index. This allows the feature to be enabled in the service when per-(C-S, C-G) stream configuration is present. Only entries that are not shut down are evaluated. First, the multi-stream S-PMSI (the lowest policy index) that the (C-S, C-G) stream maps to is selected.

2. If (C-S, C-G) does not map to any of multi-stream S-PMSIs, per-(C-S, C-G) S-PMSIs are used for transmission if a (C-S, C-G) maps to an existing S-PMSI (based on data-thresholds).

3. If S-PMSI cannot be used, the default PMSI is used.

To address multi-stream S-PMSI P-tunnel failure, if an S-PMSI P-tunnel is not available, a default PMSI tunnel is used. When an S-PMSI tunnel fails, all (C-S, C-G) streams using this multi-stream S-PMSI move to the default PMSI. The groups move back to S-PMSI after the S-PMSI tunnel is restored.

A single data MDT can transport one or more IPv4 (C-S, C-G) streams. This allows multiple multicast streams starting from the same VPRN going to the same set of leafs to use a single data MDT. Characteristics of an MDT include:

• a multi-stream data MDT can carry IPv4 only

• a multi-stream data MDT can coexist with a single-group data MDT

• a default MDT must be configured

To create a multi-stream MDT data, an MDA data policy must be configured in the context of MVPN on the source node. This policy maps multiple (C-S, C-G) streams to a single data MDT. Because this configuration is per MVPN, multiple VPNs can have identical policies configured, each for its own VPN context.

When a multicast stream is mapped to a multi-stream data MDT policy, the data traverses the default MDT first. The data delay timer is used to switch the data from the default MDT to the multi-stream data MDT.

When the multi-stream data MDT is deleted, the traffic switches back to the default MDT.

In some cases when a new multi-stream data MDT is configured which is better suited, some streams may prefer this new multi-stream data MDT. To switch, the traffic switches to the default MDT and then to the new multi-stream data MDT.

MDT data can be configured as SSM or ASM.

There can be multiple multi-stream policies assigned to a single data MDT configuration. In this case, the policy acts as a link list, the first (lowest index) matched multi-stream policy is used for that specific stream. The following are the rules of matching a multi-stream data MDT to (C-S, C-G) mapping on a source PE (in order):

1. The multi-stream policy is evaluated to enable the feature in service when per-(C-S, C-G) configuration is present, starting from the lowest numerical policy index (only entries that are not shutdown are evaluated). The first multi-stream data MDT (the lowest policy index) the (C-S, C-G) maps to is selected.

2. If (C-S, C-G) does not map to any of the multi-stream data MDTs, per-(C-S, C-G) single data MDTs are used if a (C-S, C-G) maps to an existing MDT based on data-thresholds.

3. The default MDT is used if no policy matches to a data MDT.

4. When a (C-S, C-G) arrives, it start on the default MDT but can switch to a data MDT when the data delay interval expires. It does not check the data-threshold before switching.

5. When going from one multi-stream data MDT to a more suitable one, the traffic first switches to the default MDT and then switch to the new multi-stream data MDT based on the data-delay-interval.

When a data MDT tunnel fails, all (C-S, C-G)s using this multi-stream data MDT move to the default MDT, and the groups move back to the data MDT when it is restored.

Multicast extranet is supported for Rosen MVPN with MDT SAFI. Extranet is supported for IPv4 multicast stream for default and data MDTs (PIM and IGMP).

The following extranet cases are supported:

• local replication into a receiver VRF from a source VRF on a source PE

• transit replication from a source VRF onto a tunnel of a transit core VRF on a source PE. A source VRF can replicate its streams into multiple core VRFs as long as any specific stream from source VRF uses a single core VRF (the first tunnel in any core VRF on which a join for the stream arrives). Streams with overlapping group addresses (same group address, different source address) are supported in the same core VRF.

• remote replication from source or transit VRF into one or more receiver VRFs on receiver PEs

• multiple replications from multiple source or transit VRFs into a receiver VRF on receiver PEs

Rosen MVPN extranet requires routing information exchange between the source VRF and the receiver VRF based on route export or import policies:

• Routing information for multicast sources must be exported using an RT export policy from the source VRF instance.

• Routing information must be imported into the receiver or transit VRF instance using an RT import policy.

The following are restrictions:

• The source VRF instance and receiver VRF instance of extranet must exist on a common PE node (to allow local extranet mapping).

• SSM translation is required for IGMP (C-*, C-G).

• An I-PMSI route cannot be imported into multiple VPRNs, and NG-MVPN routes do not need to be imported into multiple VPRNs.

In Multicast VPN traffic flow, VPRN-1 is the source VPRN instance and VPRN-2 and VPRN-3 are receiver VPRN instances. The PIM/IGMP JOIN received on VPRN-2 or VPRN-3 is for (S1, G1) multicast flow. Source S1 belongs to VPRN-1. Because of the route export policy in VPRN-1 and the import policy in VPRN-2 and VPRN-3, the receiver host in VPRN-2 or VPRN-3 can subscribe to the stream (S1, G1).

Multicast extranet is supported for ng-MVPN with IPv4 RSVP-TE and mLDP I-PMSIs and S-PMSIs including (C-*, C-*) S-PMSI support where applicable. Extranet is supported for IPv4 C-multicast traffic (PIM/IGMP joins).

The following extranet cases are supported:

• local replication into a receiver C-instance MVPNs on a source PE from a source P-instance MVPN

• remote replication from P-instance MVPN into one or more receiver C-instance MVPNs on receiver PEs

• multiple replications from multiple source/transit P-instance MVPNs into a receiver C-instance MVPN on receiver PEs

Multicast extranet for ng-MVPN, similarly to extranet for Rosen MVPN, requires routing information exchange between source ng-MVPN and receiver ng-MVPN based on route export and import policies. Routing information for multicast sources is exported using an RT export policy from a source ng-MVPN instance and imported into a receiver ng-MVPN instance using an RT import policy. S-PMSI/I-PMSI establishment and C-multicast route exchange occurs in a source ng-MVPN P-instance only (import and export policies are not used for MVPN route exchange). Sender-only functionality must not be enabled for the source/transit ng-MVPN on the receiver PE. It is recommended to enable receiver-only functionality on a receiver ng-MVPN instance.

The following are restrictions:

• Source P-instance MVPN and receiver C-instance MVPN must reside on the receiver PE (to allow local extranet mapping).

• SSM translation is required for IGMP (C-*, C-G).

In some deployments, such as IPTV or wholesale multicast services, it may be desirable to create one or more transit MVPNs to optimize delivery of multicast streams in the provider core. Source PE transit replication and receiver PE per-group SSM extranet mapping represents an example deployment model.

The architecture displayed in Source PE transit replication and receiver PE per-group SSM extranet mapping requires a source routing instance MVPN to place its multicast streams into one or more transit core routing instance MVPNs (each stream mapping to a single transit core instance only). It also requires receivers within each receiver routing instance MVPN to know which transit core routing instance MVPN they need to join for each of the multicast streams. To achieve this functionality, transit replication from a source routing instance MVPN onto a tunnel of a transit core routing instance MVPN on a source PE (see earlier sub-sections for MVPN topologies supporting transit replication on source PEs) and per-group mapping of multicast groups from receiver routing instance MVPNs to transit core routing instance MVPNs (as defined below) are required.

For per-group mapping on a receiver PE, the operator must configure a receiver routing instance MVPN per-group mapping to one or more source/transit core routing instance MVPNs. The mapping allows propagation of PIM joins received in the receiver routing instance MVPN into the core routing MVPN instance defined by the map. All multicast streams sourced from a single multicast source address are always mapped to a single core routing instance MVPN for a specific receiver routing instance MVPN (multiple receiver MVPNs can use different core MVPNs for groups from the same multicast source address). If per-group map in receiver MVPN maps multicast streams sourced from the same multicast source address to multiple core routing instance MVPNs, then the first PIM join processed for those streams selects the core routing instance MVPN to be used for all multicast streams from a specific source address for this receiver MVPN. PIM joins for streams sourced from the source address not carried by the selected core VRF MVPN instance remains unresolved. When a PIM join or prune is received in a receiver routing instance MVPN with per-group mapping configured, if no mapping is defined for the PIM join’s group address, non-extranet processing applies when resolving how to forward the PIM join/prune.

The main attributes for per-group SSM extranet mapping on receiver PE include support for:

• Rosen MVPN with MDT SAFI. RFC6513/6514 NG-MVPN with IPv4 RSVP-TE/mLDP in P-instance (a P-instance tunnel must be in the same VPRN service as multicast source)

• IPv4 PIM SSM

• IGMP (C-S, C-G), and for IGMP (C-*, C-G) using SSM translation

• a receiver routing instance MVPN to map groups to multiple core routing instance MVPNs

• in-service changes of the map to a different transit/source core routing instance (this is service affecting)

The following are restrictions:

• When a receiver routing instance MVPN is on the same PE as a source routing instance MVPN, basic extranet functionality and not per-group (C-S, C-G) mapping must be configured (extranet from receiver routing instance to core routing instance to source routing instance on a single PE is not supported).

• Local receivers in the core routing instance MVPN are not supported when per-group mapping is deployed.

• Receiver routing instance MVPN that has per-group mapping enabled cannot have tunnels in its OIF lists.

• Per-group mapping is blocked if GRT/VRF extranet is configured.

Multicast GRT-source/VRF-receiver (GRT/VRF) extranet with per-group mapping allows multicast traffic to flow from GRT into VRF MVPN instances. A VRF routing instance that received a PIM/IGMP join but cannot reach the source multicast stream directly within its own instance is selected as receiver routing instance. A GRT instance that has sources of multicast streams and accepts PIM joins from other VRF MVPN instances is selected as source routing instance.

GRT/VRF extranet shows an example deployment.

Routing information is exchanged between GRT and VRF receiver MVPN instances of extranet by enabling grt-extranet under a receiver MVPN PIM configuration for all or a subset of multicast groups. When enabled, multicast receivers in a receiver routing instances can subscribe to streams from any multicast source node reachable in GRT source instance.

The main feature attributes are:

• GRT/VRF extranet can be performed on all streams or on a configured group of prefixes within a receiver routing instance.

• GRT instance requires Classic Rosen multicast.

• IPv4 PIM joins are supported in receiver VRF instances.

• Local receivers using IGMP: (C-S, C-G) and (C-*, C-G) using SSM translation are supported.

• The feature is blocked if a per-group mapping extranet is configured in receiver VRF.

Multicast extranet with per-group mapping for PIM ASM allows multicast traffic to flow from a source routing instance to a receiver routing instance when a PIM ASM join is received in the receiver routing instance.

Multicast extranet with per group PIM ASM mapping depicts PIM ASM extranet map support.

PIM ASM extranet is achieved by local mapping from the receiver to source routing instances on a receiver PE. The mapping allows propagation of anycast RP PIM register messages between the source and receiver routing instances over an auto-created internal extranet interface. This PIM register propagation allows the receiver routing instance to resolve PIM ASM joins to multicast sources and to propagate PIM SSM joins over an auto-created extranet interface to the source routing instance. PIM SSM joins are then propagated toward the multicast source within the source routing instance.

The following MVPN topologies are supported:

• Rosen MVPN with MDT SAFI: a local replication on a source PE and multiple-source/multiple-receiver replication on a receiver PE

• RFC 6513/6514 NG-MVPN (including RFC 6625 (C-*, C-*) wildcard S-PMSI): a local replication on a source PE and a multiple source/multiple receiver replication on a receiver PE

• Extranet for GRT-source/VRF receiver with a local replication on a source PE and a multiple-receiver replication on a receiver PE

• Locally attached receivers are supported without SSM mapping.

To achieve the extranet replication, the operator must configure:

• local PIM ASM mapping on a receiver PE from a receiver routing instance to a source routing instance (config>service>vprn>mvpn>rpf-select>core-mvpn or config>service>vprn>pim>grt-extranet as applicable)

• an anycast RP mesh between source and receiver PEs in the source routing instance

The following are restrictions:

• This feature is supported for IPv4 multicast.

• The multicast source must reside in the source routing instance the ASM map points to on a receiver PE (the deployment of transit replication extranet from source instance to core instance on Source PE with ASM map extranet from receiver instance to core instance on a receiver PE is not supported).

• A specific multicast group can be mapped in a receiver routing instance using either PIM SSM mapping or PIM ASM mapping but not both.

• A specific multicast group cannot map to multiple source routing instances.

SystemIP is usually used for management purposes and, therefore, it may be needed to create services to a separate loopback interface. Because of security concerns, many operators do not want to create services to the systemIP address. See NG-MVPN setup via loopback interface and Intra-AS basic opaque FEC to loopback interface.

The first portion of this feature allows MVPN routes be advertised with a nexthop specific loopback.

This can be achieved via two methods:

• Having IBGP session to the loopback interface of the peer, and using the corresponding local loopback for local-address.

• Having IBGP session to the systemIP but using policies to change the nexthop of the AD route to the corresponding loopback interface.

After the AD routes are advertised via the loopback interface as nexthop, PIM generates an mLDP FEC for the loopback interface.

The preceding configuration allows an NG-MVPN to be established via a specific loopback.

It should be noted that this setup works in a single area or multi-area through an ABR.

In Core diversity with parallel NG-MVPN services on parallel IGP instances, Red and Blue networks correspond to separate IGP instances tied to separate loopback interfaces. In core diversity, MVPN services on the LER are bound to a domain by advertising MP-BGP routes, with next hop set to the appropriate loopback address, and having the receiving LERs resolve those BGP next hops, based on the corresponding IGP instance. All subsequent MVPN BGP routing exchanges must set and resolve the BGP next hop with the configured non-system loopback.

With this feature, an MP-BGP next hop would resolve to a link LDP label which is indirectly associated with a specific IGP instance. Services which advertise BGP routes with next hop Red loopback would result in traffic flowing over the Red network using LDP and Blue loopback would result in traffic flowing over Blue network. See Core diversity with parallel NG-MVPN services on parallel IGP instances.

Most importantly, the common routes in each IGP instance must have a unique and active label. This is required to ensure that the same route advertised in two different IGP domains do not resolve to the same label. LDP local-lsr-id can be used to ensure FECs and label mapping be advertised via the right instance of IGP.

Core diversity allows an operator to optionally deploy multicast NG-MVPN in either default IGP instance or one of the non-default IGP instances to provide, for example, topology isolation or different level of services. The following describes the main feature attributes:

• NG- MVPN can use IPv4/IPv6 multicast.

• NG-MVPN can use a non-default OSPF or ISIS instance.

  Note: This is accomplished by using their loopback addresses instead of a system address.

• The BGP Connector also uses non-default OSPF loopback as NH, via two methods:

  • Setting the BGP local-address to a loopback interface IP address

  • Creating a routing policy to set the NH of a MVPN AD route to the corresponding loopback IP

• RSVP-TE/LDP transport tunnels also use non-systemIP loopback for session creation. As an example, RSVP-TE p2mp LSPs would be created to non systemIP loopbacks and mLDP creates a session via local-lsr-id.

• Need to add the source-address for mvpn auto-discover default.

On the source PEs, a NG-MVPN is assigned to a non-default IGP core instance as follows:

1. NG-MVPN is statically pointed to use one of the non-default red/blue IGP instances loopback addresses as source address instead of system loopback IP.

2. MVPN export policy is used to change unicast route next-hop VPN address (BGP Connector support for non-default instances).

3. Alternatively, the BGP local-address can be set to the correct loopback interface assigned for that specific instance.

The preceding configuration ensures that MVPN-IPv4/v6 and IP-VPN routes for the non-default core instance use non-default IGP loopback instead of system IP. This ensures MVPN-IPv4/v6 advertisement/joins run in the correct core instance and mLDP and P2MP RSVP tunnels (I-PMSI and S-PMSI) for multicast can be set-up using and terminating on non-system IP.

If BGP export policy is used to change unicast route next-hop VPN address, then unicast traffic must be forwarded in non-default red or blue core instance LDP or RSVP (terminating on non-system IP) must be used.

Each NG-MVPN can be established over a separate IGP instance for core diversity support. In P2MP RSVP-TE core diversity with UFD for UMH redundancy, there are two IGP instances, Blue and Red, each having its own dedicated NG-MVPN service. The Blue plane is identified with the system IP address, and Red plane is identified with a loopback IP address. MVPN Autodiscovery (AD) routes are advertised and installed accordingly based on their NLRI in each instance. To advertise these MVPN AD routes in the corresponding planes, route policies are used to change the next hops of the AD routes. For example, for the Blue plane the AD routes are advertised by default with the system IP address as their next hop, so no route policy is necessary. In the Red plane, a route policy can change the next hop of the corresponding NG-MVPN AD routes to use the loopback IP address.

Core diversity also supports UMH redundancy solutions. In the case of P2MP RSVP-TE, which uses UFD for source UMH failure, the UFD packets are generated for each IGP instance (Blue, Red) accordingly, with the correct source and destination IP address that is part of that IGP instance.

SR OS generates the UFD packets with the correct source and destination IP addresses for each IGP instance used in the core diversity configuration. SR OS uses the NLRI next-hop information of the AD route for the destination IP address and derives the source IP address from the MVPN autodiscovery default source-address loopback for the UFD packets. This ensures the UFD packets are traversing the appropriate core corresponding to their UMH reachability.

For example, in P2MP RSVP-TE core diversity with UFD for UMH redundancy, the Blue plane UFD packets are generated from the root PE to the leaf PE with the source IP address as the local system IP on the root and the destination IP address as the system IP of the leaf. The Red plane generates the UFD packet with the loopback IP address to which it is corresponding to as its source and destination IP address.

In Core diversity with parallel NG-MVPN services on parallel IGP instances, there are three IGP instances, the default Instance 0, Instance 1, and Instance 2. Each instance binds to its own loopback interface. For Instance 0, it is the systemIP system Interface used as loopback. LDP, RSVP and MP-BGP need to run between the corresponding loopback associated with each instance.

For example, for the blue Instance 2, both MP-BGP and LDP need to be configured to its corresponding loopback loopback2 and the next-hop for BGP MVPN-IP4/IPv6 and the VPN-IPv4/IPv6 need to be loopback2.

From a configuration point of view, the following steps need to be performed:

1. For MLDP, configure LDP with local-lsr-id with loopback interface of instance 2 loopback2:

   *A:SwSim14>config>router>ldp# info 
   
         interface-parameters
            interface ‟2ROOT” dual-stack
              ipv4
                local-lsr-id interface-name ‟loopback2”
                 no shutdown
              exit
              no shutdown
            exit
   

2. Enable the source-address for default auto discover as follows:

   *A:Dut-A>config>service>vprn 2
         mvpn auto-discovery default source-address LOOPBack1
         vrf-export ‟vprnexp100”
   *A:Dut-A>config>service>vprn 3
         mvpn auto-discovery default source-address LOOPBack2
         vrf-export ‟vprnexp101”
   

3. Define community vprnXXXX for each VPRN using non-default core-instance and define a policy to tag each VPRN with either a blue or red standard community attribute:

   *A:Dut-A>config>router>policy-options# info
           community "vprn2" members "target:70:70"
           community "vprn3" members "target:80:80"
           policy-statement "vprnexp2"
               entry 10
                   from
                      protocol direct
                   exit
                   action accept
                      community add "vprn2" "red"
                   exit
               exit
           policy-statement "vprnexp3"
               entry 10
                   from
                      protocol direct
                   exit
                   action accept
                      community add "vprn3" "blue"
                   exit
               exit
           exit
   

4. Define a single global BGP policy to change next hop for red/blue MVPNs:

   *A:Dut-A>config>router>policy-options# info
           policy-statement "MVPN_CoreDiversity_Exp"
               entry 10
                   from
                      community "red"
                   exit
                   to
                      protocol bgp-vpn
                   exit
                   action accept
                        next-hop loopback1
                   exit
               exit
               entry 20
                   from
                      community "blue"
                   exit
                   to
                      protocol bgp-vpn
                   exit
                   action accept
                        next-hop loopback2
                   exit
               exit
           exit
   

5. Configure BGP default MVPN export in the group as required:

   configure router bgp group "mvpn" export "MVPN_CoreDiveristy_Exp"
   

6. Configure each VPRN to use correct IGP source address and correct VRF export policy:

   *A:Dut-A>config>service>vprn 2
         mvpn auto-discovery default source-address loopback1
         vrf-export "vprnexp2"
   *A:Dut-A>config>service>vprn 3
         mvpn auto-discovery default source-address loopback2
         vrf-export "vprnexp3"
   

BGP connector attribute is a transitive attribute (unchanged by intermediate BGP speaker node) that is carried with VPNv4 advertisements. It specifies the address of source PE node that originated the VPNv4 advertisement.

With Inter-AS MVPN Option B, BGP next-hop is modified by local and remote ASBR during re-advertisement of VPNv4 routes. On BGP next-hop change, information about the originator of prefix is lost as the advertisement reaches the receiver PE node.

BGP connector attribute allows source PE address information to be available to receiver PE, so that a receiver PE is able to associate VPNv4 advertisement to the corresponding source PE.

In case of Inter-AS MVPN Option B, routing information toward the source PE is not available in a remote AS domain, because IGP routes are not exchanged between ASes. Routers in an AS other than that of a source PE, have no routes available to reach the source PE and therefore PIM JOINs would never be sent upstream. To enable setup of MDT toward a source PE, BGP next-hop (ASBR) information from that PE's MDT-SAFI advertisement is used to fake a route to the PE. If the BGP next-hop is a PIM neighbor, the PIM JOINs would be sent upstream. Otherwise, the PIM JOINs would be sent to the immediate IGP next-hop (P) to reach the BGP next-hop. Because the IGP next-hop does not have a route to source PE, the PIM JOIN would not be propagated forward unless it carried extra information contained in RPF Vector.

In case of Inter-AS MVPN Option C, unicast routing information toward the source PE is available in a remote AS PEs/ASBRs as BGP 8277 tunnels, but unavailable at remote P routers. If the tunneled next-hop (ASBR) is a PIM neighbor, the PIM JOINs would be sent upstream. Otherwise, the PIM JOINs would be sent to the immediate IGP next-hop (P) to reach the tunneled next-hop. Because the IGP next-hop does not have a route to source PE, the PIM JOIN would not be propagated forward unless it carried extra information contained in RPF Vector.

To enable setup of MDT toward a source PE, PIM JOIN therefore carries BGP next hop information in addition to source PE IP address and RD for this MVPN. For option-B, both these pieces of information are derived from MDT-SAFI advertisement from the source PE. For option-C, both these pieces of information are obtained from the BGP tunneled route.

The RPF vector is added to a PIM join at a PE router when configure router pim rpfv option is enabled. P routers and ASBR routers must also have the option enabled to allow RPF Vector processing. If the option is not enabled, the RPF Vector is dropped and the PIM JOIN is processed as if the PIM Vector were not present.

For further details about RPF Vector processing please see [RFCs 5496, 5384 and 6513]

Inter-AS Option B is supported for Rosen MVPN PIM SSM using BGP MDT SAFI, PIM RPF Vector and BGP Connector attribute. The Inter-AS Option B default MDT setup depict set-up of a default MDT:

SR OS inter-AS Option B is designed to be standard compliant based on the following RFCs:

RFC 5384

The Protocol Independent Multicast (PIM) Join Attribute Format

RFC 5496

The Reverse Path Forwarding (RPF) Vector TLV

RFC 6513

Multicast in MPLS/BGP IP VPNs

The SR OS implementation was designed also to interoperate with older routers Inter-AS implementations that do not comply with the RFC 5384 and RFC 5496.

Inter-AS Option C is supported for Rosen MVPN PIM SSM using BGP MDT SAFI and PIM RPF Vector. Inter-AS Option C default MDT setup depicts a default MDT setup:

Additional restrictions for Inter-AS MVPN Option B and C support are the following:

• Inter-AS MVPN Option B is not supported with duplicate PE addresses.

• For Inter-AS Option C, BGP 8277 routes are installed into unicast rtm (rtable-u), unless routes are installed by some other means into multicast rtm (rtable-m), and Option C does not build core MDTs, therefore, rpf-table is configured to rtable-u or both.

Additional Cisco interoperability notes are the following:

RFC 5384

The Protocol Independent Multicast (PIM) Join Attribute Format

RFC 5496

The Reverse Path Forwarding (RPF) Vector TLV

RFC 6513

Multicast in MPLS/BGP IP VPNs

The SR OS implementation was designed to inter-operate with Cisco routers Inter-AS implementations that do not comply with the RFC5384 and RFC5496.

When configure router pim rpfv mvpn option is enabled, Cisco routers need to be configured to include RD in an RPF vector using the following command: ip multicast vrf vrf-name rpf proxy rd vector for interoperability. When Cisco routers are not configured to include RD in an RPF vector, operator should configure SR OS router (if supported) using configure router pim rpfv core mvpn: PIM joins received can be a mix of core and mvpn RPF vectors.

This feature allows multicast services to use segmented protocols and span them over multiple autonomous systems (ASs), as done in unicast services. As IP VPN or GRT services span multiple IGP areas or multiple ASs, either because of a network designed to deal with scale or as result of commercial acquisitions, operators may require Inter-AS VPN (unicast) connectivity. For example, an Inter-AS VPN can break the IGP, MPLS and BGP protocols into access segments and core segments, allowing higher scaling of protocols by segmenting them into their own islands. SR OS also allows for similar provision of multicast services and for spanning these services over multiple IGP areas or multiple ASs.

For multicast VPN (MVPN), SR OS previously supported Inter-AS Model A/B/C for Rosen MVPN; however, when MPLS was used, only Model A was supported for Next Generation Multicast VPN (NG-MVPN) and d-mLDP signaling.

For unicast VPRNs, the Inter-AS or Intra-AS Option B and C breaks the IGP, BGP and MPLS protocols at ABR routers (in case of multiple IGP areas) and ASBR routers (in case of multiple ASs). At ABR and ASBR routers, a stitching mechanism of MPLS transport is required to allow transition from one segment to next, as shown in Unicast VPN Option B with segmented MPLS and Unicast VPN Option C with segmented MPLS.

In Unicast VPN Option B with segmented MPLS, the Service Label (S) is stitched at the ASBR routers.

In Unicast VPN Option C with segmented MPLS, the 8277 BGP Label Route (LR) is stitched at ASBR1 and ASBR3. At ASBR1, the LR1 is stitched with LR2, and at ASBR3, the LR2 is stitched with TL2.

Previously, in case of NG-MVPN, segmenting an LDP MPLS tunnel at ASBRs or ABRs was not possible. As such, RFC 6512 and 6513 used a non-segmented mechanism to transport the multicast data over P-tunnels end-to-end through ABR and ASBR routers. The signaling of LDP needed to be present and possible between two ABR routers or two ASBR routers in different ASs.

SR OS now has d-mLDP non-segmented intra-AS and inter-AS signaling for NG-MVPN and GRT multicast. The non-segmented solution for d-mLDP is possible for inter-ASs as Option B and C.

For intra/inter-as option B, the root is not visible on the leaf. LDP is responsible for building the recursive FEC and signaling the FEC to ABR/ASBR on the leaf. ABR/ASBR must have the PMSI AD router to re-build the FEC (recursive or basic) depending on whether they are connected to another ABR/ASBR or root node. As such, LDP must import the MVPN PMSI AD routes. To save resources, importing MVPN PMSI AD routes are performed manually by the operator using configuration commands. When mvpn-no-export-community command is enabled, LDP requests BGP to provide the LDP task with all the MVPN PMSI AD routes and LDP internally caches these routes. If this knob is disabled and to save resources, MVPN discards the catch routes.

In a scenario where a node running an older image that does not support the mvpn-no-export-community command and that node upgrades to a new image that does support the mvpn-no-export-community command, and if the older image had an inter-as MVPN configuration, then after the upgrade to the newer image, the mvpn-no-export-community command is enabled by default, to ensure a smooth upgrade. This is to verify that all the routes are imported to mLDP so the inter-as functionality works after the upgrade.

In addition, SR OS supports two major upgrades to enable the MVPN command if an upgrade to a load supporting this knob.

For option B, the ABR routers must change the next-hop of MVPN AD routes to be the ABR systemIP or the loopback IP for core diversity. Currently, the next-hop-self BGP command does not change the next hop of the MVPN AD routes. This functionality will be available in a future release.

In the meantime, a BGP policy can be used to change the MVPN AD routes next hop at the ABR.

<S,G> switching between I-PMSI and S-PMSI is not symmetrical (synchronized in time) on the active and the inactive UMH. While the active UMH attempts to switch an <S,G> between I-PMSI and S-PMSI, the active PMSI traffic rate arriving from the active UMH may be different from that arriving from the inactive UMH. This asymmetrical behavior can generate a premature switch from the active PMSI to the inactive PMSI.

The traffic rate delta can be set to account for this behavior. For example, if a 1080P channel uses 5 Mb/s, the traffic rate delta can be set to 15 Mb/s to avoid the switchover from the primary to the secondary PMSI if one or two 1080 <S,G>s are switched between I-PMSI and S-PMSI. This provides a 10 Mb/s tolerance of asymmetric traffic.

If the network FDV is large or the sources are not synchronized, switching from I-PMSI to S-PMSI can happen at a different time on the primary and backup UMHs. This can cause asymmetric traffic on the I-PMSI and S-PMSI, resulting in a switch from the active UMH. The <S,G> traffic can arrive for the I-PMSI from the backup UMH and for S-PMSI from the active UMH, which causes temporary duplicate traffic until both UMHs switch to S-PMSI.

Multistream S-PMSI provides a solution for this case by mapping an <S,G> to an S-PMSI. The <S,G> is locked to the multistream S-PMSI, which is always configured and never torn down, even if the traffic goes down to 0, so the multistream S-PMSI is not susceptible to S-PMSI traffic drops.

The number of <S,G>s must be less than, or equal to, the maximum-p2mp-spmsi value configured under the MVPN selective provider tunnel. Otherwise, different <S,G>s can switch to the S-PMSI and when the S-PMSI limit is exhausted, the 2 UMHs become out of sync.

Bandwidth monitoring is supported on single IOMs, that is, both the active and the backup PMSI terminate on the same IOM. The IOM monitors the statistics of both PMSIs and makes the switchover decision. The IOM does not include the CPM in any of the bandwidth monitoring decisions, which ensures fast detection times and switchover times under 50 ms.

All leaf and bud nodes must be configured with the same UMH PEs, I-PMSI and S-PMSI, and bandwidth threshold configuration to avoid traffic drops.

All LAG members must be in the same IOM that is performing the bandwidth monitoring function. The LAG interfaces spanning between multiple port members that belong to different IOMs have an unpredictable behavior, including traffic duplication.

Bandwidth monitoring is supported with ASM only after the traffic is switched from <*,G> to <S,G>. Traffic arriving on separate IOMs from the active UMH and the inactive UMH results in traffic duplication because the pairing of the active and inactive UMH is per IOM, and the IOMs do not have a view of the pair. If the active traffic and the backup traffic arrive on different IOMs, each IOM treats the flow as the active flow and processes the traffic accordingly.

At low traffic rates, the packet on the active PMSI and the packet on the inactive PMSI can arrive at different times. If the packets arrive at the point that the statistics are read, there can be an inconsistency, resulting in a switchover. To avoid a switchover, UMH redundancy using bandwidth monitoring should be used only when the traffic rate is higher than 2 or 3 packets per second.

If the active PMSI traffic goes below the threshold while the revertive timer (configure service vprn mvpn provider-tunnel inclusive umh-rate-monitoring revertive-timer and configure service vprn mvpn provider-tunnel selective umh-rate-monitoring group source revertive-timer) is running, the timer is reset.

Multicast-only Fast Reroute (MoFRR) is not supported when UMH redundancy with bandwidth monitoring is enabled.

Use the following CLI syntax to create a VPRN service. A route distinguisher must be defined and the VPRN service must be administratively up in order for VPRN to be operationally active.

config>service# vprn service-id [customer customer-id]
    — route-distinguisher [ip-address:number1 | asn:number2]
    — description description-string
    — no shutdown

The following example displays a VPRN service configuration.

*A:ALA-1>config>service# info
----------------------------------------------
...
        vprn 1 customer 1 create
            route-distinguisher 10001:0
            no shutdown
        exit
...
----------------------------------------------
*A:ALA-1>config>service>vprn# 

The following example displays a VPRN service with configured parameters.

*A:ALA-1>config>service# info
----------------------------------------------
...
        vprn 1 customer 1 create
            vrf-import "vrfImpPolCust1"
            vrf-export "vrfExpPolCust1"
            autonomous-system 10000
            route-distinguisher 10001:1
            spoke-sdp 2 create
            exit
            no shutdown
        exit
...
----------------------------------------------
*A:ALA-1>config>service# 

The following output displays a VPRN log configuration example.

B:Dut-C>config>service>vprn# info 
----------------------------------------------
            dhcp
                local-dhcp-server "vprn_1" create
                    use-pool-from-client
                    force-renews
                    no shutdown
                exit
            exit
            snmp
                 community "YsMv96H2KZVKQeakNAq.38gvyr.MH9vA" hash2 r version both
                 community "gkYL94l90FFgu91PiRNvn3Rnl0edkMU1" hash2 rw version v2c
                 access
            log
                filter 1 
                    default-action forward
                    entry 1 
                        action forward
                    exit 
                exit 
                syslog 1
                    address 3ffe::e01:403
                    log-prefix "vprn1"
                exit 
                snmp-trap-group 32001
                    trap-target "3" address 3ffe::e01:403 port 9000 snmpv2c notify-
community "vprn1"
                exit 
                log-id 1 
                    filter 1 
                    from main change 
                    to syslog 1
                exit 
                log-id 3 
                    filter 1 
                    from main change 
                    to snmp
                exit 
            exit
...
----------------------------------------------
B:Dut-C>config>service>vprn# 

The following example displays a VPRN PIM configuration for the 7750 SR:

config>service# info
#------------------------------------------
...
        vprn 1 customer 2 create
            route-distinguisher 1:11
            interface "if1" create
                address 10.13.14.15/32
                loopback
            exit
            interface "if2" create
                address 10.13.14.1/24
                sap 1/1/2:0 create
                exit
            exit
            pim
                interface "if1"
                exit
                interface "if2"
                exit
                rp
                    static
                    exit
                    bsr-candidate
                        shutdown
                    exit
                    rp-candidate
                        shutdown
                    exit
                exit
            exit
            no shutdown
        exit
    exit
#------------------------------------------
config>service#