VLL services

Two modes of circuit emulation are supported: unstructured and structured. Unstructured mode is supported for DS1 and E1 channels per RFC 4553, Structure-Agnostic Time Division Multiplexing (TDM) over Packet (SAToP). Structured mode is supported for N*64 kb/s circuits as per RFC 5086, Structure-Aware Time Division Multiplexed (TDM) Circuit Emulation Service over Packet Switched Network (CESoPSN). Also, DS1, E1, and N*64 kb/s circuits are supported (per MEF8). TDM circuits are optionally encapsulated in MPLS or Ethernet as per the referenced standards in the following examples.

The following figure shows an example of RFC 4553 (SAToP) MPLS PSN encapsulation.

The following figure shows an example of CESoPSN packet format for an MPLS PSN.

The following figure shows an example of MEF8 PSN encapsulation.

Each circuit can be optionally encapsulated in MPLS, Ethernet packets. Circuits encapsulated in MPLS use circuit pipes (Cpipes) to connect to the far-end circuit. Cpipes support either SAP spoke-SDP or SAP-SAP connections. Cpipes are supported over MPLS and GRE tunnels. The Cpipe default service MTU is set to 1514 bytes.

Circuits encapsulated in Ethernet can be selected as a SAP in Epipes. Circuits encapsulated in Ethernet can be SAP spoke-SDP connections or Ethernet CEM SAP-to-Ethernet SAP for all valid Epipe SAPs. Circuits requiring CEM SAP-to-CEM SAP connections use Cpipes. A local and remote EC-ID and far-end destination MAC address can be configurable for each circuit. The MDA MAC address is used as the source MAC address for these circuits.

For all service types, there are deterministic PIR=CIR values with class=EF parameters based on the circuit emulation parameters.

All circuit emulation services support the display of status of up, loss of packet (LOP), or admin down. Also, any jitter buffer overruns or underruns are logged.

Non-stop services are supported for Cpipes and CES over Epipes.

Each OC-3/STM-1 port can be independently configured to be loop-timed or node-timed. Each OC-3/STM-1 port can be configured to be a timing source for the node. TDM satellites only support node-timed mode.

Each DS-1 or E-1 channel without CAS signaling enabled can be independently configured to be loop-timed, node-timed, adaptive-timed, or differential-timed. Each DS-1 or E-1 channel with CAS signaling enabled can be independently configured to be loop-timed or node-timed. Adaptive timing and differential timing are not supported on DS-1 or E-1 channels with CAS signaling enabled. For the TDM satellite, each DS1/E1 channel can be loop-timed, node-timed, or differential-timed.

The adaptive recovered clock of a CES circuit can be used as a timing reference source for the node (ref1 or ref2). This is required to distribute network timing to network elements that only have packet connectivity to the network. One timing source on the MDA can be monitored for timing integrity. Both timing sources can be monitored if they are configured on separate MDAs while respecting the timing subsystem slot requirements.

If a CES circuit is being used for adaptive clock recovery at the remote end (such that the local end is now an adaptive clock master), Nokia recommends setting the DS-1/E-1 to be node-timed to prevent potential jitter issues in the recovered adaptive clock at the remote device. This is not applicable to TDM satellites.

For differential-timed circuits, the following timestamp frequencies are supported: 103.68 MHz (for recommended >100 MHz operation), 77.76 MHz (for interoperability with SONET/SDH-based systems such as TSS-5) and 19.44 MHz (for Y.1413 compliance). TDM satellite supports only 77.76 MHz.

Adaptive and differential timing recovery must comply with published jitter and wander specifications (G.823, G.824, and G.8261) for traffic interfaces under typical network conditions and for synchronous interfaces under specified packet network delay, loss, and delay variance (jitter) conditions. The packet network requirements to meet the synchronous interface requirements are to be determined during the testing phase.

CESoPSN MPLS payload format shows the format of the CESoPSN TDM payload (with and without CAS) for packets carrying trunk-specific 64 kb/s service. In CESoPSN, the payload size is dependent on the number of timeslots used. This is not applicable to TDM satellite because only unstructured DS1/E1 is supported.

An Epipe service is the Nokia implementation of an Ethernet VLL based on the IETF "Martini Drafts" (draft-martini-l2circuit-trans-mpls-08.txt and draft-martini-l2circuit-encapmpls-04.txt) and the IETF Ethernet Pseudowire Draft (draft-so-pwe3-ethernet-00.txt).

An Epipe service is a Layer 2 point-to-point service where the customer data is encapsulated and transported across a service provider IP, MPLS, or Provider Backbone Bridging (PBB) VPLS network. An Epipe service is completely transparent to the customer data and protocols. The Epipe service does not perform any MAC learning. A local Epipe service consists of two SAPs on the same node, whereas a distributed Epipe service consists of two SAPs on different nodes. SDPs are not used in local Epipe services.

Each SAP configuration includes a specific port or channel on which service traffic enters the router from the customer side (also called the access side). Each port is configured with an encapsulation type. If a port is configured with an IEEE 802.1Q (referred to as dot1q) encapsulation, a unique encapsulation value (ID) must be specified.

Distributed Epipe services are connected using a pseudowire, which can be provisioned statically or dynamically and is represented in the system as a spoke-SDP. The spoke-SDP can be configured to process zero, one, or two VLAN tags as traffic is transmitted and received; see Epipe spoke-SDP VLAN tag processing: ingress and Epipe-spoke SDP VLAN tag processing: egress for the ingress and egress tag processing. In the transmit direction, VLAN tags are added to the frame being sent. In the received direction, VLAN tags are removed from the frame being received. This is analogous to the SAP operations on a null, dot1q, and QinQ SAP.

The system expects a symmetrical configuration with its peer; specifically, it expects to remove the same number of VLAN tags from received traffic as it adds to transmitted traffic. When removing VLAN tags from a spoke-SDP, the system attempts to remove the configured number of VLAN tags. If fewer tags are found, the system removes the VLAN tags found and forwards the resulting packet.

Because some of the related configuration parameters are local and not communicated in the signaling plane, an asymmetrical behavior cannot always be detected and so cannot be blocked. With an asymmetrical behavior, a protocol extraction does not necessarily function as it would with a symmetrical configuration, resulting in an unexpected operation.

The VLAN tag processing is configured as follows on a spoke-SDP in an Epipe service:

• zero VLAN tags processed

  This requires the configuration of vc-type ether under the spoke-SDP, or in the related PW template.

• one VLAN tag processed

  This requires one of the following configurations:

  • vc-type vlan under the spoke-SDP or in the related PW template

  • vc-type ether and force-vlan-vc-forwarding under the spoke-SDP or in the related PW template

• two VLAN tags processed

  This requires the configuration of force-qinq-vc-forwarding [c-tag-c-tag | s-tag-c-tag] under the spoke-SDP or in the related PW template.

The PW template configuration provides support for BGP VPWS services.

The following restrictions apply to VLAN tag processing:

• The configuration of vc-type vlan and force-vlan-vc-forwarding is mutually exclusive.

• force-qinq-vc-forwarding [c-tag-c-tag | s-tag-c-tag] can be configured with the spoke-SDP signaled as either vc-type ether or vc-type vlan.

• The following are not supported with force-qinq-vc-forwarding [c-tag-c-tag | s-tag-c-tag] configured under the spoke-SDP, or in the related PW template:

  • Multi-segment pseudowires.

  • PBB-Epipe services

  • force-vlan-vc-forwarding under the same spoke-SDP or PW template

  • Eth-CFM LM tests are NOT supported on UP MEPs when force-qinq-vc-forwarding is enabled.

Epipe spoke-SDP VLAN tag processing: ingress and Epipe-spoke SDP VLAN tag processing: egress describe the VLAN tag processing with respect to the zero, one, and two VLAN tag configuration described for the VLAN identifiers, Ethertype, ingress QoS classification (dot1p or DE), and QoS propagation to the egress (which can be used for egress classification and, or to set the QoS information in the innermost egress VLAN tag).

Any non-service delimiting VLAN tags are forwarded transparently through the Epipe service. SAP egress classification is possible on the outermost customer VLAN tag received on a spoke-SDP using the ethernet-ctag parameter in the associated SAP egress QoS policy.

By default, the operational state of the Epipe is tied to the state of the two connections that comprise the Epipe. If either of the connections in the Epipe are operationally down, the Epipe service that contains that connection is also operationally down. The operator can configure a single SAP within an Epipe that does not affect the operational state of that Epipe, using the optional ignore-oper-state command. Within an Epipe, if a SAP that includes this optional command becomes operationally down, the operational state of the Epipe does not transition to down. The operational state of the Epipe remains up. This does not change that the SAP is down and no traffic can transit an operationally down SAP. Removing and adding this command on the fly evaluates the operational state of the service, based on the SAPs and the addition or deletion of this command.

Service OAM (SOAM) designers may consider using this command if an operationally up MEP configured on the operationally down SAP within an Epipe is required to receive and process SOAM PDUs. When a service is operationally down, this is not possible. For SOAM PDUs to continue to arrive on an operationally up, MEP configured on the failed SAP, the service must be operationally up. Consider the case where an operationally up MEP is placed on a UNI-N or E-NNI and the UNI-C on E-NNI peer is shutdown in such a way that it causes the SAP to become operationally down.

Two connections must be configured within the Epipe; otherwise, the service is operationally down regardless of this command. The ignore-oper-state functionality only operates as intended when the Epipe has one ingress and one egress. This command is not to be used for Epipe services with redundant connections that provide alternate forwarding in case of failure, even though the CLI does not prevent this configuration.

Support is available on Ethernet SAPs configured on ports or Ethernet SAPs configured on LAG. However, it is not allowed on SAPs using LAG profiles or if the SAP is configured on a LAG that has no ports.

A PBB tunnel may be linked to an Epipe to a B-VPLS. MAC switching and learning is not required for the point-to-point service. All packets that ingress the SAP are PBB encapsulated and forwarded to the PBB tunnel to the backbone destination MAC address. Likewise, all the packets that ingress the B-VPLS destined for the ISID are PBB de-encapsulated and forwarded to the Epipe SAP. A fully specified backbone destination address must be provisioned for each PBB Epipe instance to be used for each incoming frame on the related I-SAP. If the backbone destination address is not found in the B-VPLS FDB, packets may be flooded through the B-VPLSs.

All B-VPLS constructs may be used including B-VPLS resiliency and OAM. Not all generic Epipe commands are applicable when using a PBB tunnel.

The L2TPv3 feature provides a framework to transport Ethernet pseudowire services over an IPv6-only network without MPLS. This architecture relies on the abundance of address space in the IPv6 protocol to provide unique far-end and local-end addressing that uniquely identify each tunnel and service binding.

L2TPv3 provides the capability of transporting multiple Epipes (up to 16K per system), by binding multiple IPv6 addresses to each node and configuring one SDP per Epipe.

Because the IPv6 addressing uniqueness identifies the customer and service binding, the L2TPv3 control plane is disabled in this mode.

L2TPv3 is supported on non-12e 7750 SR, 7450 ESS, and 7950 XRS platforms.

ETH-CFM is supported for OAM services.

Application of Ethernet interworking VLL provides an example of an Ethernet interworking VLL. The Ethernet interworking VLL provides a point-to-point Ethernet VLL service between Frame Relay (FR) attached users, ATM-attached users, and Ethernet-attached users across an IP/MPLS packet switched network. It effectively provides ATM and FR bridged encapsulation termination on the existing Epipe service of the 7750 SR.

The following connectivity scenarios are supported:

• a Frame Relay or ATM user connected to a ATM network communicating with a Ethernet user connected to a PE node on a IP/MPLS network

• a Frame Relay or ATM user connected to PE node communicating with an Ethernet user connected to a PE node on an IP/MPLS network. This feature supports local cross-connecting when these users are attached to the same PE node.

Users attach over an ATM UNI with RFC 2684, Multiprotocol Encapsulation over ATM Adaptation Layer 5, tagged/untagged bridged Ethernet PDUs, a FR UNI using RFC 2427, Multiprotocol Interconnect over Frame Relay, tagged/untagged bridged Ethernet PDUs, or an Ethernet tagged/untagged UNI interface. However, the VCI/VPI and the data-link connection identifier (DLCI) are the identifiers of the SAP in the case of ATM and FR, respectively, and the received tags are transparent to the service, so are preserved.

The Ethernet pseudowire is established using T-LDP signaling and can use the ether or vlan VC types on the SDP. The SDP can be either an MPLS or GRE type.

The VLL Connection Admission Control (CAC) is supported for the 7750 SR only and provides a method to administratively account for the bandwidth used by VLL services inside an SDP that consists of RSVP LSPs.

The service manager keeps track of the available bandwidth for each SDP. The SDP available bandwidth is applied through a configured booking factor. An administrative bandwidth value is assigned to the spoke-SDP. When a VLL service is bound to an SDP, the amount of bandwidth is subtracted from the adjusted available SDP bandwidth. When the VLL service binding is deleted from the SDP, the amount of bandwidth is added back into the adjusted SDP available bandwidth. If the total adjusted SDP available bandwidth is overbooked when adding a VLL service, a warning is issued and the binding is rejected.

This feature does not guarantee bandwidth to a VLL service because there is no change to the data path to enforce the bandwidth of an SDP by means such as shaping or policing of constituent RSVP LSPs.

To support redundant VLL access in ring configurations, the multi-chassis ring (MC-Ring) feature is applicable to VLL SAPs. A conceptual drawing of the operation is shown in MC-Ring in a combination with VLL service. The specific CPE that is connected behind the ring node has access to both BSAs through the same VLAN provisioned in all ring nodes. There are two SAPs (with the same VLAN) provisioned on both nodes.

If a closed ring status occurs, one of the BSAs becomes the primary BSA and signals an active status bit on the corresponding VLL pseudowire. Similarly, the standby BSA signals a standby status. With this information, the remote node can choose the correct path to reach the CPE. In case of a broken ring, the node that can reach the ring node, to which the CPE is connected by RNCV check, becomes the primary and signals corresponding status on its pseudowire.

The mapping of individual SAPs to the ring nodes is done statically through CLI provisioning. To keep the convergence time to a minimum, MAC learning must be disabled on the ring node so all CPE originated traffic is sent in both directions. If the status is operationally down on the SAP on the standby BSA, that part of the traffic is blocked and not forwarded to the remote site.

For further information about Multi-Chassis Ring Layer 2 (with ESM), see the 7450 ESS, 7750 SR, and 7950 XRS Advanced Configuration Guide.

IP interworking VLL (Ipipe) provides an example of IP connectivity between a host attached to a point-to-point access circuit (FR, ATM, PPP) with routed PDU IPv4 encapsulation and a host attached to an Ethernet interface. Both hosts appear to be on the same LAN segment. This feature is supported for the 7450 ESS and 7750 SR and enables service interworking between different link layer technologies. A typical use of this application is in a Layer 2 VPN when upgrading a hub site to Ethernet while keeping the spoke sites with their existing Frame Relay or ATM IPv4 routed encapsulation.

In IP interworking VLL (Ipipe), PE 2 is manually configured with both CE 1 and CE 2 IP addresses. These are host addresses and are entered in /32 format. PE 2 maintains an ARP cache context for each IP interworking VLL. PE 2 responds to ARP request messages received on the Ethernet SAP. PE 2 responds with the Ethernet SAP configured MAC address as a proxy for any ARP request for CE 1 IP address. PE 2 silently discards any ARP request message received on the Ethernet SAP for an address other than that of CE 1. Likewise, PE 2 silently discards any ARP request message with the source IP address other than that of CE 2. In all cases, PE 2 keeps track of the association of IP to MAC addresses for ARP requests it receives over the Ethernet SAP.

To forward unicast frames destined for CE 2, PE 2 needs to know the CE 2 MAC address. When the Ipipe SAP is first configured and administratively enabled, PE2 sends an ARP request message for CE 2 MAC address over the Ethernet SAP. Until an ARP reply is received from CE2, providing the CE2 MAC address, unicast IP packets destined for CE2 are discarded at PE2. IP broadcast and IP multicast packets are sent on the Ethernet SAP using the broadcast or direct-mapped multicast MAC address.

To forward unicast frames destined for CE 1, PE 2 validates the MAC destination address of the received Ethernet frame. The MAC address should match that of the Ethernet SAP. PE 2 then removes the Ethernet header and encapsulates the IP packet directly into a pseudowire without a control word. PE 1 removes the pseudowire encapsulation and forwards the IP packet over the Frame Relay SAP using RFC 2427, Multiprotocol Interconnect over Frame Relay, routed PDU encapsulation.

To forward unicast packets destined for CE1, PE2 validates the MAC destination address of the received Ethernet frame. If the IP packet is unicast, the MAC destination must match that of the Ethernet SAP. If the IP packet is multicast or broadcast, the MAC destination address must be an appropriate multicast or broadcast MAC address.

The other procedures are similar to the case of communication between CE 1 and CE 2, except that the ATM SAP and the Ethernet SAP are cross-connected locally and IP packets do not get sent over an SDP.

A PE does not flush the ARP cache unless the SAP goes administratively or operationally down. The PE with the Ethernet SAP sends unsolicited ARP requests to refresh the ARP cache every ‟T” seconds. ARP requests are staggered at an increasing rate if no reply is received to the first unsolicited ARP request. The value of T is configurable by the user through the mac-refresh command.

VLL services provide IP connectivity between a host attached to a point-to-point access circuit with routed PDU encapsulation and a host attached to an Ethernet interface. Both hosts appear to be on the same IP interface. This feature is supported only for IPv4 payload.

In deployments where it is not practical for operators to obtain and configure their customer CE address, the following behaviors apply:

• A service comes up without prior configuration of the CE address parameter under both the SAP and the spoke-SDP.

• Operators rely solely on received ARP messages from the Ethernet SAP-attached CE device to update the ARP cache with no further check of the validity of the source IP address of the ARP request message and the target IP address being resolved.

• The LDP address list TLV signaling the learned CE IP address to the remote PE is supported. This is to allow the PE with the FR SAP to respond to an invFR ARP request message received from the FR-attached CE device. Only Ethernet SAP and FR SAP can learn the CE address through ARP and invFR ARP, respectively. The 7450 ESS and 7750 SR do not support invATM ARP on an ATM interface.

The 7450 ESS, 7750 SR, and 7950 XRS nodes support both the transport of IPv6 packets and the interworking of IPv6 Neighbor discovery/solicitation messages on an IP Interworking VLL. IPv6 capability is enabled on an Ipipe using the ce-address-discovery ipv6 command.

Only MPLS SDPs are supported.

An SDP used for MPLS-TP supports the configuration of an MPLS-TP identifier as the far-end address as an alternative to an IP address. IP addresses are used if IP/MPLS LSPs are used by the SDP, or if MPLS-TP tunnels are identified by IPv4 source/destination addresses. MPLS-TP node identifiers are used if MPLS-TP tunnels are used.

Only static SDPs with signaling off support MPLS-TP spoke-SDPs.

The following CLI shows the MPLS-TP options:

config
   service
      sdp 10 [mpls | GRE | [ldp-enabled] [create] 
         signaling <off | on> 
         [no] lsp <xyz> 
         [no] accounting-policy <policy-id>
         [no] adv-mtu-override
         [no] booking-factor <percentage>
         [no] class-forwarding
         [no] collect-stats
         [no] description <description-string>
         [no] far-end <ip-address> | [node-id 
              {<ip-address> | <0…4,294,967,295>} [global-id <global-id>]]
         [no] tunnel-far-end <ip-address> 
         [no] keep-alive
         [no] mixed-lsp-mode
         [no] metric <metric>
         [no] network-domain <network-domain-name>
         [no] path-mtu <mtu>  
         [no] pbb-etype <ethertype>
         [no] vlan-vc-etype <ethertype>
         [no] shutdown 

The far-end node-id ip-address global-id global-id command is used to associate an SDP far end with an MPLS-TP tunnel whose far-end address is an MPLS-TP node ID. If the SDP is associated with an RSVP-TE LSP, the far end must be a routable IPv4 address.

The system accepts the node-id being entered in either 4-octet IP address format (a.b.c.d) or unsigned integer format.

The SDP far end refers to an MPLS-TP node-id/global-id only if:

• delivery type is MPLS

• signaling is off

• keep-alive is disabled

• mixed-lsp-mode is disabled

• adv-mtu-override is disabled

An LSP can only be allowed to be configured if the far-end information matches the lsp far end information (whether MPLS-TP or RSVP).

• Only one LSP is allowed if the far end is an MPLS-TP node-id/global-id.

• MPLS-TP or RSVP-TE LSPs are supported. However, LDP and BG LSPs are not blocked in CLI.

Signaling LDP or BGP is blocked if:

• far-end node-id/global-id is configured

• control-channel-status is enabled on any spoke (or mate vc-switched spoke)

• pw-path-id is configured on any spoke (or mate vc-switched spoke)

• IES/VPRN interface spoke control-word is enabled

The following commands are blocked if a far-end node-id/global-id is configured:

• class-forwarding

• tunnel-far-end

• mixed-lsp-mode

• keep-alive

• ldp or bgp-tunnel

• adv-mtu-override

The system can be a T-PE or an S-PE for a pseudowire (a spoke-SDP) supporting MPLS-TP OAM. MPLS-TP related commands are applicable to spoke-SDPs configured under all services supported by MPLS-TP pseudowires. All commands and functions that are applicable to spoke-SDPs are supported, except for those that explicitly depend on T-LDP signaling of the pseudowire, or as stated following. Likewise, all existing functions on a specified service SAP are supported if the spoke-SDP that it is mated to is MPLS-TP.

The vc-switching is supported.

The following describes how to configure MPLS-TP on an Epipe VLL. However, a similar configuration applies to other VLL types.

A spoke-SDP bound to an SDP with the mpls-tp keyword cannot be no shutdown unless the ingress label, the egress label, the control word, and the pw-path-id are configured, as follows:

config
   service
      epipe
         [no] spoke-sdp sdp-id[:vc-id]
              [no] hash-label
              [no] standby-signaling-slave

         [no] spoke-sdp sdp-id[:vc-id] [vc-type {ether | vlan}]
             [create] [vc-switching] [no-endpoint | {endpoint [icb]}] 
            egress
               vc-label <out-label>
            ingress
               vc-label <in-label>
            control-word 
            bandwidth <bandwidth> 
            [no] pw-path-id 
               agi <agi> 
               saii-type2 <global-id:node-id:ac-id>
               taii-type2 <global-id:node-id:ac-id>
               exit
            [no] control-channel-status 
[no] refresh-timer <value> 
request-timer <request-timer-secs> retry-timer <retry-timer-secs> timeout-
multiplier <multiplier>
no request-timer
               [no] acknowledgment 
               [no] shutdown
               exit

The pw-path-id context is used to configure the end-to-end identifiers for an MS-PW. These may not coincide with those for the local node if the configuration is at an S-PE. The SAII and TAII are consistent with the source and destination of a label mapping message for a signaled PW.

The control-channel-status command enables static pseudowire status signaling. This is valid for any spoke-SDP where signaling none is configured on the SDP (for example, where T-LDP signaling is not in use). The refresh timer is specified in seconds, from 10-65535, with a default of 0 (off). This value can only be changed if control-channel-status is shutdown.

Commands that rely on PW status signaling are allowed if control-channel-status is configured for a spoke-SDP bound to an SDP with signaling off, but the system uses control channel status signaling instead of T-LDP status signaling. The ability to configure control channel status signaling on a specified spoke-SDP is determined by the credit-based algorithm described earlier. Control channel status for a pseudowire only counts against the credit-based algorithm if the pseudowire is in a no shutdown state and has a non-zero refresh timer and a non-zero request timer.

A shutdown of a service results in the static PW status bits for the corresponding PW being set.

The spoke-SDP is held down unless the pw-path-id is complete.

The system accepts the node-id of the pw-path-id saii or taii being entered in either 4-octet IP address format (a.b.c.d) or unsigned integer format.

The control-word must be enabled to use MPLS-TP on a spoke-SDP.

The optional acknowledgment to a static PW status message is enabled using the acknowledgment command. The default is no acknowledgment.

The pw-path-id is only configurable if all of the following are true:

• in network mode D

• sdp signaling is off

• control-word is enabled (control-word is disabled by default)

• on service type Epipe, VPLS, Cpipe, or IES/VPRN interface

• An MPLS-TP node-id/global-id is configured under the config>router>mpls>mpls-tp context. This is required for OAM to provide a reply address.

In the vc-switching case, if configured to make a static MPLS-TP spoke SDP to another static spoke SDP, the TAII of the spoke-SDP must match the SAII of its mate, and the SAII of the spoke-SDP must match the TAII of its mate.

A control-channel-status no shutdown is allowed only if all of the following are true:

• in network-mode D

• sdp signaling is off

• control-word is enabled (control-word by default is disabled)

• the service type is Epipe, VPLS, Cpipe, or IES/VPRN interface

• pw-status-signaling is enabled (as follows)

• pw-path-id is configured for this spoke

The hash-label option is only configurable if SDP far end is not node-id/global-id.

The control channel status request mechanism is enabled when the request-timer timer parameter is non-zero. When enabled, this overrides the normal RFC-compliant refresh timer behavior. The refresh timer value in the status packet defined in RFC 6478 is always set to zero. The refresh-timer in the sending node is taken from the request-timer <timer1> timer. The two mechanisms are not compatible with each other. One node sends a request timer while the other is configured for refresh timer. In a specified node, the request timer can only be configured with both acknowledgment and refresh timers disabled.

When configured, the procedures following are used instead of the RFC 6478 procedures when a PW status changes.

The CLI commands to configure control channel status requests are as follows:

[no] control-channel-status 
     [no] refresh-timer <value> //0,10-65535, default:0 
     [no] request-timer <timer1> retry-timer <timer2> 
                  [timeout-multiplier <value>]
     [no] shutdown
     exit

request-timer <timer1>: 0, 10-65535, defaults: 0.

This parameter determines the interval at which PW status messages are sent, including a reliable delivery TLV, with the ‟request” bit set (as follows). This cannot be enabled if refresh-timer is not equal to zero (0).

retry-timer <timer2>: 3 to 60s

This parameter determines the timeout interval if no response to a PW status is received. This defaults to zero (0) when no retry-timer.

timeout-multiplier <value>: 3 to 15

If a requesting node does not get a response after retry-timer ✕ multiplier, the node must assume that the peer is down. This defaults to zero (0) when no retry-timer.

MPLS-TP supports lock instruct and loopback for PWs.

Some use cases for MPLS-TP require an MPLS-TP based aggregation network and an IP-based core network to interoperate, so providing the seamless transport of packet services across static MPLS-TP and dynamically signaled domains using an MS-PW. In this environment, end-to-end VCCV Ping and VCCV Trace may be used on the MS-PW, as shown in Static - dynamic PW switching with MPLS-TP.

Services are backhauled from the static MPLS-TP network on the left to the dynamic IP/MPLS network on the right. The router acts as an S-PE interconnecting the static and dynamic domains.

The router implementation supports such use cases through the ability to mate a static MPLS-TP spoke SDP, with a defined pw-path-id, to a FEC128 spoke SDP. The dynamically signaled spoke SDP must be MPLS; GRE PWs are not supported, but the T-LDP signaled PW can use any supported MPLS tunnel type (for example, LDP, RSVP-TE, static, BGP). The control-word must be enabled on both mate spoke SDPs.

Mapping of control channel status signaling to and from T-LDP status signaling at the router S-PE is also supported.

The use of VCCV Ping and VCCV Trace on an MS-PW composed of a mix of static MPLS-TP and dynamic FEC128 segments is described in more detail in the 7450 ESS, 7750 SR, 7950 XRS, and VSR OAM and Diagnostics Guide.

The SR OS supports RFC 5885, which specifies a method for carrying BFD in a pseudowire-associated channel. This enables BFD to monitor the pseudowire between its terminating PEs, regardless of how many P routers or switching PEs the pseudowire may traverse. This makes it possible for faults that are local to individual pseudowires to be detected, whether they also affect forwarding for other pseudowires, LSPs, or IP packets. VCCV BFD is ideal for monitoring specific high-value services, where detecting forwarding failures (and potentially restoring from them) in the minimal amount of time is critical.

VCCV BFD is supported on VLL services using T-LDP spoke-SDPs or BGP VPWS. It is supported for Cpipe, Epipe, and Ipipe VLL services.

VCCV BFD is supported on IES/VPRN services with T-LDP spoke -SDP termination (for Epipes and Ipipes).

VCCV BFD is supported on LDP- and BGP-signaled pseudowires, and on pseudowires with statically configured labels, whether signaling is off or on for the SDP. VCCV BFD is not supported on MPLS-TP pseudowires.

VCCV BFD is supported on VPLS services (both spoke-SDPs and mesh SDPs). VCCV BFD is configured by:

1. configuring generic BFD session parameters in a BFD template

2. applying the BFD template to a spoke-SDP or pseudowire-template binding, using the bfd-template bfd-template-name command

3. enabling the template on that spoke-SDP, mesh SDP, or pseudowire-template binding using the bfd-enable command

The SR OS supports IP/UDP encapsulation for BFD. With this encapsulation type, the UDP headers are included on the BFD packet. IP/UDP encapsulation is supported for pseudowires that use router alert (VCCV Type 2), and for pseudowires with a control word (VCCV Type 1). In the control word case, the IPv4 channel (channel type 0x0021) is used. On the node, the destination IPv4 address is fixed at 127.0.0.1 and the source address is 127.0.0.2.

VCCV BFD sessions run end-to-end on a switched pseudowire. They do not terminate on an intermediate S-PE; therefore, the TTL of the pseudowire label on VCCV BFD packets is always set to 255 to ensure that the packets reach the far-end T-PE of an MS-PW.

BFD packets flow along the full length of a PW, from T-PE to T-PE. Because they are not intercepted at an S-PE, single-hop initialization procedures are used.

A single BFD session exists per pseudowire.

BFD runs in asynchronous mode.

BFD operates as a simple connectivity check on a pseudowire. The BFD session state is displayed in the MIBs and in the show>service id>sdp>vccv-bfd session command. By default, BFD is not used to change the operational state of the pseudowire, to modify pseudowire redundancy, or to map the BFD state to SAP OAM. However, the router may be optionally configured to take into account the BFD session state.

VCCV BFD runs in software with a minimum supported timer interval of 100 ms for Epipe LDP spoke-SDP; H-VPLS spoke-SDP and mesh-SDP; and Epipe spoke-SDP termination on IES and VPRN interfaces, and inter-chassis backup spoke-SDPs.

BFD is used only for fault detection. While RFC 5885 provides a mode in which VCCV BFD can be used to signal pseudowire status, this mode is applicable only to pseudowires that have no other status signaling mechanism in use. LDP status and static pseudowire status signaling always take precedence over BFD-signaled PW status, and BFD-signaled pseudowire status is not used on pseudowires that use LDP status or static pseudowire status signaling mechanisms.

Use the failure-action down command to configure the router to use the VCCV BFD session state to affect the operational status of its SDP bindings (spoke-SDPs or mesh-SDPs). This behaviour is only supported for Epipe LDP spoke-SDPs, H-VPLS spoke-SDPs, inter-chassis backup spoke-SDPs, and Epipe spoke-SDP termination on IES and VPRN interfaces.

If this behavior is configured on a spoke-SDP bound to a VPLS or VPLS component of the R-VPLS, the SDP binding operational state is treated as an operationally down PW by the VPLS. This means that if all SDP bindings in the VPLS instance go operationally down because the VCCV BFD is going down, the VPLS goes down. In the case of R-VPLS, this handling is required to take down the associated IP interface if all SDP bindings are down. An operational down state that is caused by the BFD session going down removes the SDP binding from the eligible set used for PW redundancy in a VPLS or VLL service, including spoke SDP termination on IES or VPRN interfaces.

An operational down state of the SDP binding, because the VCCV BFD session is going down, is mapped to any SAP OAM mechanisms. It also contributes to the operational state of an operational group that is monitoring the SDP binding on which VCCV BFD with failure-action down is configured.

Generic BFD session parameters are configured for VCCV using the bfd-template command, in the config>router>bfd context. However, there are some restrictions.

For VCCV, the BFD session cannot terminate on the CPM network processor. Therefore, an error is generated if the user tries to bind a BFD template using the type cpm-np command within the config>router>bfd>bfd-template context.

Attempting to bind a BFD template with any unsupported transmit or receive interval generates an error.

Finally, attempting to commit changes to a BFD template that is already bound to a PW where the new values are invalid for VCCV BFD results in an error.

If the preceding BFD timer values are changed in a specified template, any BFD sessions on PWs to which that template is bound try to renegotiate their timers to the new values.

Commands within the BFD-template use a begin-commit model. To edit any value within the BFD template, a begin command needs to be executed after the template context has been entered. However, a value is still stored temporarily in the template-module until the commit command is issued. When the commit is issued, values are used by other modules such as the MPLS-TP module and BFD module.

For PWs where the PW template does not apply, a named BFD template is configured on the spoke-SDP using the config service [epipe | cpipe | apipe | fpipe | ipipe] spoke-sdp bfd bfd-template command and then enabled using the config service [epipe | cpipe | apipe | fpipe | ipipe] spoke-sdp bfd bfd-enable command. For example, LDP-signaled spoke-SDPs for a VLL service that uses the PW ID FEC (FEC128) or spoke-SDPs with static PW labels.

Configuring and enabling a BFD template on a static PW already configured with MPLS-TP identifiers (that is, with a pw-path-id) or on a spoke-SDP with a configured pw-path-id is not supported. Likewise, if a BFD template is configured and enabled on a spoke-SDP, a pw-path-id cannot be configured on the spoke-SDP.

The bfd-enable command is blocked on a spoke-SDP configured with VC-switching. This is because VCCV BFD always operates end-to-end on an MS-pseudowire. It is not possible to extract VCCV BFD packets at the S-PE.

For IES and VPRN spoke-SDP termination where the PW template does not apply (that is, where the spoke-SDP is signaled with LDP and uses the PW ID FEC (FEC128)), the BFD template is configured using the config service ies | vprn if spoke-sdp bfd bfd-template command, then enabled using the config service ies | vprn if spoke-sdp bfd bfd-enable command.

For H-VPLS, where the PW template does not apply (that is, LDP-VPLS spoke SDPs that use the PW ID FEC(FEC128)) the BFD template is configured using the configure service vpls spoke-sdp bfd bfd-template or the configure service vpls mesh-sdp bfd bfd-template command. VCCV BFD is then enabled with the bfd-enable command under the vpls spoke-sdp bfd or vpls mesh-sdp bfd context.

PWs where the PW template does apply and that support VCCV BFD are as follows:

• BGP-AD, which is signaled using the Generalized PW ID FEC (FEC129) with Attachment Individual Identifier (AII) type I

• BGP VPLS

• BGP VPWS

For these PW types, a named BFD template is configured and enabled from the PW template binding context.

For BGP VPWS, the BFD template is configured using the config service epipe bgp pw-template-binding bfd-template name command, then enabled using the config service epipe bgp pw-template-binding bfd-enable command.

The ability to determine PW forwarding state from VCCV BFD on the pseudowire is configured using the failure-action down command. It is possible to configure failure-action whether a spoke-SDP is administratively shutdown or not. It is therefore recommended to first configure VCCV BFD to ensure the spoke-SDP is forwarding, and then configure the failure-action command. If the failure-action down command is configured, the router continues to send VCCV BFD packets on a spoke-SDP or mesh-SDP that is operationally down because of the VCCV BFD session being in the down state. The router can then rapidly detect when connectivity is restored.

The wait-for-up-timer can be configured when failure-action down is configured. The wait-for-up-timer timer is triggered when a spoke-SDP or mesh-SDP is first administratively enabled and when a VCCV BFD session transitions from up to down. It is useful to allow time for BFD sessions to come up when the spoke-SDP is initially no shutdown. This provides the BFD session time to settle before it selects the active spoke-SDP for use in a redundant set. It also prevents excessive flapping of the operation state of a spoke-SDP if a VCCV BFD session is bouncing.

Pseudowire switching scales VLL and VPLS services over a multi-area network by removing the need for a full mesh of targeted LDP sessions between PE nodes. VLL resilience with pseudowire redundancy and switching shows the use of pseudowire redundancy to provide a scalable and resilient VLL service across multiple IGP areas in a provider network.

In the network in VLL resilience with pseudowire redundancy and switching, PE nodes act as leading nodes, and pseudowire switching nodes act as followers for the purpose of pseudowire signaling. A switching node needs to pass the SAP interface parameters of each PE to the other PEs. T-PE1 sends a label mapping message for the Layer 2 FEC to the peer pseudowire switching node; for example, S-PE1. The label mapping message includes the SAP interface parameters, such as MTU, in the label mapping message. S-PE1 checks the FEC against the local information and, if a match exists, appends the optional pseudowire switching point TLV to the FEC TLV in which it records its system address. T-PE1 then relays the label mapping message to S-PE2. S-PE2 performs similar operations and forwards a label mapping message to T-PE2.

The same procedures are followed for the label mapping message in the reverse direction; for example, from T-PE2 to T-PE1. S-PE1 and S-PE2 make the spoke-SDP cross-connect only when both directions of the pseudowire are signaled and matched.

The pseudowire switching TLV is useful in a few situations. First, it allows for troubleshooting of the path of the pseudowire, especially if multiple pseudowire switching points exist between the two T-PE nodes. Second, it helps in loop detection of the T-LDP signaling messages where a switching point receives back a label mapping message that the point already relayed. Finally, it can be inserted in pseudowire status messages when they are sent from a pseudowire switching node toward a destination PE.

Pseudowire status messages can be generated by the T-PE nodes and, or the S-PE nodes. Pseudowire status messages received by a switching node are processed and passed on to the next hop. An S-PE node appends the optional pseudowire switching TLV, with the S-PEs system address added to it, to the FEC in the pseudowire status notification message, only if that S-PE originated the message or the message was received with the TLV in it. Otherwise, the message was originated by a T-PE node and the S-PE should process and pass the message without changes, except for the VC-ID value in the FEC TLV.

In the network in VLL resilience with pseudowire redundancy and switching, PE nodes act as leading nodes and pseudowire switching nodes act as followers for the purpose of pseudowire signaling. This is because a switching node needs to pass the SAP interface parameters of each PE to the other. T-PE1 sends a label mapping message for the Layer 2 FEC to the peer pseudowire switching node; for example, S-PE1. It includes the SAP interface parameters, such as MTU, in the label mapping message. S-PE1 checks the FEC against the local information and, if a match exists, appends the optional pseudowire switching point TLV to the FEC TLV in which it records its system address. T-PE1 then relays the label mapping message to S-PE2. S-PE2 performs similar operation and forwards a label mapping message to T-PE2.

The same procedures are followed for the label mapping message in the reverse direction; for example, from T-PE2 to T-PE1. S-PE1 and S-PE2 affect the spoke-SDP cross-connect only when both directions of the pseudowire are signaled and matched.

Pseudowire status messages can be generated by the T-PE nodes and, or the S-PE nodes. Pseudowire status messages received by a switching node are processed, then passed on to the next hop. An S-PE node appends the optional pseudowire switching TLV, with its system address added to it, to the FEC in the pseudowire status notification message, only if it originated the message or the message was received with the TLV in it. Otherwise, the message was originated by a T-PE node and the S-PE should process and pass the message without changes, except for the VC-ID value in the FEC TLV.

The merging of the received T-LDP status notification message and the local status for the spoke-SDPs from the service manager at a PE complies with the following rules:

• When the local status for both spoke-SDPs is up, the S-PE passes any received SAP or SDP binding generated status notification message unchanged; for example, the status notification TLV is unchanged but the VC-ID in the FEC TLV is set to value of the pseudowire segment to the next hop.

• When the local operational status for any of the spokes is down, the S-PE always sends an SDP-binding down status bits regardless of whether the received status bits from the remote node indicated SAP up or down or SDP-binding up or down.

When one segment of the pseudowire cross-connect at the S-PE is static while the other is signaled using T-LDP, the S-PE operates much like a T-PE from a signaling perspective and as an S-PE from a data plane perspective.

The S-PE signals a label mapping message as soon as the local configuration is complete. The control word C-bit field in the pseudowire FEC is set to the value configured on the static spoke-SDP.

When the label mapping for the egress direction is also received from the T-LDP peer, and the information in the FEC matches that of the local configuration, the static-to-dynamic cross-connect is created.

It is possible that end nodes of a static pseudowire segment can be misconfigured. In this case, an S-PE or T-PE node may be receiving packets with the wrong encapsulation, so that an invalid payload could be forwarded over the pseudowire or the SAP, respectively. Also, if the S-PE or T-PE node is expecting the control word in the packet encapsulation and the received packet comes with no control word, but the first nibble below the label stack is 0x0001, the packet may be mistaken for a VCCV OAM packet and may be forwarded to the CPM. In that case, the CPM performs a check of the IP header fields such as version, IP header length, and checksum. If any of these fail the VCCV packet is discarded.

This feature is supported on VPLS and VLL services where the end-to-end solution is built using two node solutions (requiring SDP connections between the nodes).

In VLAN swapping, only the VLAN ID value is copied to the inner VLAN position. The Ethertype of the inner tag is preserved and all consecutive nodes work with that value. Similarly, the dot1p bits value of outer tag is not preserved.

Ingress VLAN swapping shows a network where, at user-access side (DSLAM-facing SAPs), every subscriber is represented by several QinQ SAPs with inner-tag encoding service and outer tag encoding subscriber (DSL line). At the aggregation side (BRAS- or PE-facing SAPs) every subscriber is represented by DSL line number (inner VLAN tag) and DSLAM (outer VLAN tag). The effective operation on the VLAN tag is to drop the inner tag at the access side and push another tag at the aggregation side.

Pseudowire redundancy provides the ability to protect a pseudowire with a pre-provisioned secondary standby pseudowire and to switch traffic over to that secondary standby pseudowire in case of a SAP and, or network failure condition. Normally, pseudowires are redundant by the virtue of the SDP redundancy mechanism. For instance, if the SDP is an RSVP LSP and is protected by a secondary standby path and, or by Fast-Reroute paths (FRR), the pseudowire is also protected. However, there are two applications in which SDP redundancy does not protect the end-to-end pseudowire path:

• There are two different destination PE nodes for the same VLL service. The main use case is the provision of dual-homing of a CPE or access node to two PE nodes located in different POPs. The other use case is the provision of a pair of active and standby BRAS nodes, or active and standby links to the same BRAS node, to provide service resiliency to broadband service subscribers.

• The pseudowire path is switched in the middle of the network and the pseudowire switching node fails.

Pseudowire and VPLS link redundancy extends link-level resiliency for pseudowires and VPLS to protect critical network paths against physical link or node failures. These innovations enable the virtualization of redundant paths across the metro or core IP network to provide seamless and transparent fail-over for point-to-point and multi-point connections and services. When deployed with multi-chassis LAG, the path for return traffic is maintained through the pseudowire or VPLS switchover, which enables carriers to deliver ‟always on” services across their IP/MPLS networks.

This section describes an example of how to configure Dynamic MS-PWs for a VLL service between a set of Nokia nodes. The network consists of two T-PEs and two nodes, in the role of S-PEs, as shown in the following figure. Each 7750 SR, 7450 ESS, or 7950 XRS peers with its neighbor using LDP and BGP.

The example uses BGP to route dynamic MS-PWs and T-LDP to signal them. Therefore, each node must be configured to support the MS-PW address family under BGP, and BGP and LDP peerings must be established between the T-PEs/S-PEs. The appropriate BGP export policies must also be configured.

Next, pseudowire routing must be configured on each node. This includes an S-PE address for every participating node, and one or more local prefixes on the T-PEs. MS-PW paths and static routes may also be configured.

When this routing and signaling infrastructure is established, spoke-sdp-fecs can be configured on each of the T-PEs, as follows:

config
   router
      ldp
         targeted-session
            peer 10.20.1.5
            exit
         exit
      policy-options
         begin
         policy-statement "exportMsPw"
            entry 10
               from
                  family ms-pw
               exit
               action accept
               exit
            exit
         exit
         commit
      exit
      bgp
         family ms-pw
         connect-retry 1
         min-route-advertisement 1
         export "exportMsPw" 
         rapid-withdrawal          
         group "ebgp"
            neighbor 10.20.1.5
               multihop 255
               peer-as 200
            exit
         exit
     exit
config
   service
      pw-routing
         spe-address 3:10.20.1.3
         local-prefix 3:10.20.1.3 create
         exit
         path "path1_to_F" create
            hop 1 10.20.1.5
            hop 2 10.20.1.2
            no shutdown
        exit
     exit
     epipe 1 name "XYZ Epipe 1" customer 1 create
        description "Default epipe
             description for service id 1"
        service-mtu 1400
        sap 2/1/1:1 create
        exit
        spoke-sdp-fec 1 fec 129 aii-type 2 create
           retry-timer 10
           retry-count 10
           saii-type2 3:10.20.1.3:1
           taii-type2 6:10.20.1.6:1
           no shutdown
        exit
        no shutdown
     exit
config
   router
      ldp
         targeted-session
            peer 10.20.1.2
            exit
         exit
         …
      policy-options
         begin
         policy-statement "exportMsPw"
            entry 10
               from
                  family ms-pw
               exit
               action accept
               exit
            exit
         exit
         commit
      exit
      
      bgp
         family ms-pw
         connect-retry 1
         min-route-advertisement 1
         export "exportMsPw" 
         rapid-withdrawal          
         group "ebgp"
            neighbor 10.20.1.2
               multihop 255
               peer-as 300
            exit
         exit
     exit
config
   service
      pw-routing
         spe-address 6:10.20.1.6
         local-prefix 6:10.20.1.6 create
         exit
         path "path1_to_F" create
            hop 1 10.20.1.2
            hop 2 10.20.1.5
            no shutdown
        exit
     exit
     epipe 1 name "XYZ Epipe 1" customer 1 create
        description "Default epipe
             description for service id 1"
service-mtu 1400
        sap 1/1/3:1 create
        exit
        spoke-sdp-fec 1 fec 129 aii-type 2 create
           retry-timer 10
           retry-count 10
           saii-type2 6:10.20.1.6:1
           taii-type2 3:10.20.1.3:1
           no shutdown
        exit
        no shutdown
     exit

config
   router
      ldp
         targeted-session
            peer 10.20.1.3
            exit
            peer 10.20.1.2
            exit
         exit
         …
      bgp
         family ms-pw
         connect-retry 1
         min-route-advertisement 1
         rapid-withdrawal          
         group "ebgp"
            neighbor 10.20.1.2
               multihop 255
               peer-as 300
            exit
            neighbor 10.20.1.3
               multihop 255
               peer-as 100
            exit
         exit
     exit

   service
      pw-routing
         spe-address 5:10.20.1.5
      exit

config
   router
      ldp
         targeted-session
            peer 10.20.1.5
            exit
            peer 10.20.1.6
            exit
         exit
         …
      bgp
         family ms-pw
         connect-retry 1
         min-route-advertisement 1
         rapid-withdrawal          
         group "ebgp"
            neighbor 10.20.1.5
               multihop 255
               peer-as 200
            exit
            neighbor 10.20.1.6
               multihop 255
               peer-as 400
            exit           
         exit
     exit
service
      pw-routing
         spe-address 2:10.20.1.2
      exit

VLL resilience shows the application of pseudowire redundancy to provide Ethernet VLL service resilience for broadband service subscribers accessing the broadband service on the service provider BRAS.

If the Ethernet SAP on PE2 fails, PE2 notifies PE1 of the failure by either withdrawing the primary pseudowire label it advertised or by sending a pseudowire status notification with the code set to indicate a SAP defect. PE1 receives it and immediately switches its local SAP to forward over the secondary standby spoke-SDP. To avoid black holing of packets during the switching of the path, PE1 accepts packets received from PE2 on the primary pseudowire while transmitting over the backup pseudowire. However, in other applications such as those described in Access node resilience using MC-LAG and pseudowire redundancy, it is important to minimize service outage to end users.

When the SAP at PE2 is restored, PE2 updates the new status of the SAP by sending a new label mapping message for the same pseudowire FEC or by sending pseudowire status notification message indicating that the SAP is back up. PE1 then starts a timer and reverts to the primary at the expiry of the timer. By default, the timer is set to 0, which means PE1 reverts immediately. A special value of the timer (infinity) means that PE1 should never revert to the primary pseudowire.

The behavior of the pseudowire redundancy feature is the same if PE1 detects or is notified of a network failure that brought the spoke-SDP status to operationally down. The following events cause PE1 to trigger a switchover to the secondary standby pseudowire.

• The T-LDP peer (remote PE) node withdraws the pseudowire label.

• The T-LDP peer signals a FEC status indicating a pseudowire failure or a remote SAP failure.

• The T-LDP session to peer node times out.

• The SDP binding or VLL service goes down as a result of a network failure condition, such as the SDP to the peer node going operationally down, or the SDP binding going operationally down because the VCCV BFD session is going down.

The SDP type for the primary and secondary pseudowires need not be the same. That is, the user can protect an RSVP-TE based spoke-SDP with an LDP or GRE based one. This provides the ability to route the path of the two pseudowires over different areas of the network. All VLL service types, for example, Epipe and Ipipe, are supported on the 7750 SR.

Nokia routers support the ability to configure multiple secondary standby pseudowire paths. For example, PE1 uses the value of the user-configurable precedence parameter associated with each spoke-SDP to select the next available pseudowire path after the failure of the current active pseudowire (whether it is the primary or one of the secondary pseudowires). The revertive operation always switches the path of the VLL back to the primary pseudowire though. There is no revertive operation between secondary paths, meaning that the path of the VLL is not switched back to a secondary pseudowire of higher precedence when the latter comes back up again.

Nokia routers support the ability for a user-initiated manual switchover of the VLL path to the primary or any of the secondary, be supported to divert user traffic in case of a planned outage such as in node upgrade procedures.

On the 7750 SR, this application can make use of all types of VLL supported on SR-series routers. However, if a SAP is configured on an MC-LAG instance, only the Epipe service type is allowed.

For information about how to use pseudowire SAPs with Layer 2 services, see the 7450 ESS, 7750 SR, 7950 XRS, and VSR Layer 3 Services Guide: IES and VPRN.

Using Epipe in combination with G.8031 and BGP multihoming in the same manner as VPLS offers a multi-chassis resiliency option for Epipe services that is a non-learning and non-flooded service. MC-LAG (see Access node resilience using MC-LAG and pseudowire redundancy) offers access node redundancy with active/stand-by links while Ethernet tunnels offer per service redundancy with all active links and active or standby services. G.8031 offers an end-to-end service resiliency for Epipe and VPLS services. BGP-MH site support for Ethernet tunnels offers Ethernet edge resiliency for Epipe services that integrates with MPLS pseudowire redundancy.

BGP-MH site support for Ethernet tunnels shows the BGP-MH site support for Ethernet tunnels, where a G.8031 edge device (A) is configure with two provider edge switches (B and C). G.8031 is configured on the Access devices (A and F). An Epipe endpoint service is configured along with BGP Multihoming and Pseudowire Redundancy on the provider edge nodes (B/C and D/E). This configuration offers a fully redundant Epipe service.

Access node resilience shows the use of both Multi-Chassis Link Aggregation (MC-LAG) in the access network and pseudowire redundancy in the core network to provide a resilient end-to-end VLL service to the customers.

In this application, a new pseudowire status bit of active or standby indicates the status of the SAP in the MC-LAG instance in the SR-series aggregation node. All spoke-SDPs are of secondary type and there is no use of a primary pseudowire type in this mode of operation. Node A is in the active state according to its local MC-LAG instance and therefore advertises active status notification messages to both its peer pseudowire nodes; for example, nodes C and D. Node D performs the same operation. Node B is in the standby state according to the status of the SAP in its local MC-LAG instance, so advertises standby status notification messages to both nodes C and D. Node C performs the same operation.

An SR-series node selects a pseudowire as the active path for forwarding packets when both the local pseudowire status and the received remote pseudowire status indicate active status. However, an SR-series device in standby status according to the SAP in its local MC-LAG instance is capable of processing packets for a VLL service received over any of the pseudowires that are up. This is to avoid black holing of user traffic during transitions. The SR-series standby node forwards these packets to the active node by the Inter-Chassis Backup pseudowire (ICB pseudowire) for this VLL service. An ICB is a spoke-SDP used by an MC-LAG node to back up an MC-LAG SAP during transitions. The same ICB can also be used by the peer MC-LAG node to protect against network failures causing the active pseudowire to go down.

At configuration time, the user specifies a precedence parameter for each of the pseudowires that are part of the redundancy set, as described in the application in VLL resilience with two destination PE nodes. An SR-series node uses this to select which pseudowire to forward packets to in case both pseudowires show active/active for the local/remote status during transitions.

Only VLL service of type Epipe is supported in this application. Also, ICB spoke-SDP can only be added to the SAP side of the VLL cross-connect if the SAP is configured on an MC-LAG instance.

VLL resilience with pseudowire redundancy and switching shows the use of both pseudowire redundancy and pseudowire switching to provide a resilient VLL service across multiple IGP areas in a provider network.

Pseudowire switching is a method for scaling a large network of VLL or VPLS services by removing the need for a full mesh of T-LDP sessions between the PE nodes as the number of these nodes grows over time.

Like in the application in VLL resilience with two destination PE nodes, the T-PE1 node switches the path of a VLL to a secondary standby pseudowire if a network side failure caused the VLL binding status to be operationally down or if T-PE2 notified it that the remote SAP went down. This application requires that pseudowire status notification messages generated by either a T-PE node or a S-PE node be processed and relayed by the S-PE nodes.

It is possible that the secondary pseudowire path terminates on the same target PE as the primary; for example, T-PE2. This provides protection against network side failures but not against a remote SAP failure. When the target destination PE for the primary and secondary pseudowires is the same, T-PE1 normally does not switch the VLL path onto the secondary pseudowire upon receipt of a pseudowire status notification indicating the remote SAP is down, because the status notification is sent over both the primary and secondary pseudowires. However, the status notification on the primary pseudowire may arrive earlier than the one on the secondary pseudowire because of the differential delay between the paths. This causes T-PE1 to switch the path of the VLL to the secondary standby pseudowire and remain there until the status notification is cleared. Then, the VLL path is switched back to the primary pseudowire because of the revertive behavior operation. The path does not switch back to a secondary path when it comes up, even if it has a higher precedence than the currently active secondary path.

For the 7750 SR, this application can make use of all types of VLL supported on the routers; for example, Epipe and Ipipe services. A SAP can be configured on a SONET/SDH port that is part of an APS group. However, if a SAP is configured on an MC-LAG instance, only the Epipe service type is allowed.

To implement pseudowire redundancy, a VLL service accommodates more than a single object on the SAP side and on the spoke-SDP side. Redundant VLL endpoint objects shows the model for a redundant VLL service based on the concept of endpoints.

By default, a VLL service supports two implicit endpoints managed internally by the system. Each endpoint can only have one object: a SAP or a spoke-SDP.

To add more objects, up to two explicitly named endpoints may be created per VLL service. The endpoint name is locally significant to the VLL service. They are referred to as endpoint X and endpoint Y, as shown in the example in Redundant VLL endpoint objects.

In Redundant VLL endpoint objects, the Y endpoint can also have a SAP and, or an ICB spoke-SDP. The following is a list of supported endpoint objects and the applicable rules to associate the object with an endpoint of a VLL service:

• SAP

  A maximum of one SAP per VLL endpoint is supported.

• primary spoke-SDP

  The VLL service always uses this pseudowire and only switches to a secondary pseudowire when this primary pseudowire is down; the VLL service switches the path to the primary pseudowire when it is back up. The user can configure a timer to delay reverting back to primary or to never revert. A maximum of one primary spoke-SDP per VLL endpoint is supported.

• secondary spoke-SDP

  There can be a maximum of four secondary spoke-SDPs per endpoint. The user can configure the precedence of a secondary pseudowire to indicate the order in which a secondary pseudowire is activated.

• Inter-Chassis Backup (ICB) spoke-SDP

  This special pseudowire is used for MC-LAG and pseudowire redundancy applications. Forwarding between ICBs is blocked on the same node. The user has to explicitly indicate that the spoke-SDP is an ICB, at creation time. However, following are a few scenarios where the user can configure the spoke-SDP as ICB or as a regular spoke-SDP on a specified node. The CLI for those cases indicates both options.

A VLL service endpoint can only use a single active object to transmit at a specific time, but it can receive from all endpoint objects.

An explicitly named endpoint can have a maximum of one SAP and one ICB. When a SAP is added to the endpoint, only one more object of type ICB spoke-SDP is allowed. The ICB spoke-SDP cannot be added to the endpoint if the SAP is not part of an MC-LAG instance. Conversely, a SAP that is not part of an MC-LAG instance cannot be added to an endpoint that already has an ICB spoke-SDP.

An explicitly named endpoint that does not have a SAP object can have a maximum of four spoke-SDPs and includes any of the following:

• a single primary spoke-SDP

• one or many secondary spoke-SDPs with precedence

• a single ICB spoke-SDP

Using Redundant VLL endpoint objects as a reference, this section describes the rules for generating, processing, and merging T-LDP status notifications in VLL service with endpoints. Any allowed combination of objects as specified in Redundant VLL service model, can be used on endpoints X and Y. The following sections see the specific combination objects in Redundant VLL endpoint objects as an example to describe the more general rules.

Based on the previously mentioned rules, the following is an example of a failure scenario. Assuming both links are active on 7750 SR #1 and the Ethernet connection to the cell site fails (most likely failure scenario because the connection would not be protected), SDP1 would go down and the secondary SAP would be used in 7750 SR #1 and 7705 SAR, as shown in Ethernet failure at cell site.

If the active link to the Layer 2 switched network was on 7750 SR #2 at the time of the failure, SAP1 would be operationally down (because the link is in standby) and ICBA would be used. Because the RNC SAP on 7750 SR #2 is on a standby APS link, ICBA would be active and it would connect to SAP2 because SDP2 is operationally down as well.

All APS link failures would be handled through the standard pseudowire status messaging procedures for the RNC connection and through standard ICB usage for the Layer 2 switched network connection.

A single-homed BGP VPWS service is implemented as an Epipe connecting a SAP or static GRE tunnel (a spoke-SDP using a GRE SDP configured with static MPLS labels) and a BGP signaled pseudowire, maintaining the Epipe properties such as no MAC learning. The MPLS pseudowire data plane uses a two-label stack; the inner label is derived from the BGP signaling and identifies the Epipe service while the outer label is the tunnel label of an LSP transporting the traffic between the two end systems.

The following figures shows how this service would be used to provide a virtual leased line service (VLL) across an MPLS network between sites A and B.

An Epipe is configured on PE1 and PE2 with BGP VPWS enabled. PE1 and PE2 are connected to site A and B, respectively, each using a SAP. The interconnection between the two PEs is achieved through a pseudowire that is signaled using BGP VPWS updates over a specific tunnel LSP.

A BGP-VPWS service can benefit from dual-homing, as described in IETF Draft draft-ietf-bess-vpls-multihoming-01. When using dual-homing, two PEs connect to a site, with one PE being the DF for the site and the other blocking its connection to the site. On failure of the active PE, its pseudowire, or its connection to the site, the other PE becomes the designated forwarder and unblocks its connection to the site.

Pseudowire switching is supported with a BGP VPWS service allowing the cross connection between a BGP VPWS signaled spoke-SDP and a static GRE tunnel, the latter being a spoke SDP configured with static MPLS labels using a GRE SDP. No other spoke SDP types are supported. Support is not included for BGP multihoming using an active and a standby pseudowire to a pair of remote PEs.

Operational state changes to the GRE tunnel are reflected in the state of the Epipe and propagated accordingly in the BGP VPWS spoke SDP status signaling, specifically using the BGP update D and CSV bits.

The following configuration is required:

1. The Epipe service must be created using the vc-switching parameter.

2. The GRE tunnel spoke SDP must be configured using a GRE SDP with signaling off and have the ingress and egress vc-labels statically configured.

Example: BGP VPWS service configured to allow pseudowire switching

configure
    service
        sdp 1 create
            signaling off
            far-end 192.168.1.1
            keep-alive
                shutdown
            exit
            no shutdown
        exit
        pw-template 1 create
        exit
        epipe 1 customer 1 vc-switching create
            description "BGP VPWS service"
            bgp
                route-distinguisher 65536:1
                route-target export target:65536:1 import target:65536:1
                pw-template-binding 1
                exit
            exit
            bgp-vpws
                ve-name "PE1"
                    ve-id 1
                exit
                remote-ve-name "PE2"
                    ve-id 2
                exit
                no shutdown
            exit
            spoke-sdp 1:1 create
                ingress
                    vc-label 1111
                exit
                egress
                    vc-label 1122
                exit
                no shutdown
            exit
            no shutdown
        exit

The BGP signaling mechanism used to establish the pseudowires is described in the BGP VPWS standards with the following differences:

• As stated in Section 3 of RFC 6624, there are two modifications of messages when compared to RFC 4761:

  • the Encaps Types supported in the associated extended community

  • the addition of a circuit status vector sub-TLV at the end of the VPWS NLRI

• The control flags and VPLS preference in the associated extended community are based on IETF Draft draft-ietf-bess-vpls-multihoming-01.

The following figure shows the format of the BGP VPWS update extended community.

• extended community type

  This is the value allocated by IANA for this attribute is 0x800A.

• encaps type

  The encapsulation type identifies the type of pseudowire encapsulation. Ethernet VLAN (4) and Ethernet Raw mode (5), as described in RFC 4448, are the only values supported. If there is a mismatch between the Encaps Type signaled and the one received, the pseudowire is created but with the operationally down state.

• control flags

  This is control information concerning the pseudowires, see Control flags for more information.

• Layer 2 MTU

  This is the MTU to be used on the pseudowires. If the received Layer 2 MTU is zero, no MTU check is performed and the related pseudowire is established. If there is a mismatch between the local service-mtu and the received Layer 2 MTU, the pseudowire is created with the operationally down state and an MTU/Parameter mismatch indication.

• VPLS preference

  VPLS preference has a default value of zero for BGP-VPWS updates sent by the system, indicating that it is not in use. If site-preference is configured, its value is used for the VPLS preference and is also used in the local designated forwarder election.

  On receipt of a BGP VPWS update containing a non-zero value, it is used to determine to which system the pseudowire is established, as part of the VPWS update process tie-breaking rules. The BGP local preference of the BGP VPWS update sent by the system is set to the same value as the VPLS preference if the latter is non-zero, as required by the draft (as long as the D bit in the extended community is not set to 1). Consequently, attempts to change the BGP local preference when exporting a BGP VPWS update with a non-zero VPLS preference is ignored. This prevents the updates being treated as malformed by the receiver of the update.

  For inter-AS, the preference information must be propagated between autonomous systems using the VPLS preference. Consequently, if the VPLS preference in a BGP-VPWS or BGP multihoming update is zero, the local preference is copied by the egress ASBR into the VPLS preference field before sending the update to the External Border Gateway Protocol (EBGP) peer. The adjacent ingress ASBR then copies the received VPLS preference into the local preference to prevent the update from being considered malformed.

The following figure shows the pseudowire control flags.

The following bits in the Control Flags are defined:

D

Access circuit down indicator from IETF Draft draft-kothari-l2vpn-auto-site-id-01. D is 1 if all access circuits are down, otherwise D is 0.

A

Automatic site ID allocation, which is not supported. This is ignored on receipt and set to 0 on sending.

F

MAC flush indicator. This is not supported because it relates to a VPLS service. This is set to 0 and ignored on receipt.

C

Presence of a control word. Control word usage is supported. When this is set to 1, packets are sent and are expected to be received, with a control word. When this is set to 0, packets are sent and are expected to be received without a control word (by default).

S

Sequenced delivery. Sequenced delivery is not supported. This is set to 0 on sending (no sequenced delivery) and, if a non-zero value is received (indicating sequenced delivery required), the pseudowire is not created.

The BGP VPWS NLRI is based on that defined for BGP VPLS, but is extended with a circuit status vector as shown in the following figure.

The VE ID value is configured within each BGP VPWS service, the label base is chosen by the system, and the VE block offset corresponds to the remote VE ID because a VE block size of 1 is always used.

The circuit status vector is encoded as a TLV, as shown in BGP VPWS NLRI TLV extension format and Circuit status vector TLV type.

The circuit status vector is used to indicate the status of both the SAP/GRE tunnel and the status of the spoke-SDP within the local service. Because the VE block size used is 1, the most significant bit in the circuit status vector TLV value is set to 1 if either the SAP/GRE tunnel or spoke-SDP is down, otherwise it is set to 0. On receiving a circuit status vector, only the most significant byte of the CSV is examined for designated forwarder selection purposes.

If a circuit status vector length field of greater than 32 is received, the update is ignored and not reflected to BGP neighbors. If the length field is greater than 800, a notification message is sent and the BGP session restarts. Also, BGP VPWS services support a single access circuit, so only the most significant bit of the CSV is examined on receipt.

A pseudowire is established when a BGP VPWS update is received that matches the service configuration, specifically the configured route targets and remote VE ID. If multiple matching updates are received, the system to which the pseudowire is established is determined by the tie-breaking rules, as described in IETF Draft draft-ietf-bess-vpls-multihoming-01.

Traffic is sent on the active pseudowire connected to the remote designated forwarder. Traffic can be received on either the active or standby pseudowire, although no traffic should be received on the standby pseudowire because the SAP/GRE tunnel on the non-designated forwarder should be blocked.

The adv-service-mtu command can be used to override the MTU value used in BGP signaling to the far-end of the pseudowire. This value is also used to validate the value signaled by the far-end PE unless ignore-l2vpn-mtu-mismatch is also configured.

If the ignore-l2vpn-mtu-mismatch command is configured, the router does not check the value of the "Layer 2 MTU" in the "Layer2 Info Extended Community" received in a BGP update message against the local service MTU, or against the MTU value signaled by this router. The router brings up the BGP-VPWS service regardless of any MTU mismatch.

BGP VPWS with inter-AS model C is supported both in a single-homed and dual-homed configuration.

When dual-homing is used, the dual-homed PEs must have different values configured for the site-preference (under the site within the Epipe service) to allow the PEs in a different AS to select the designated forwarder when all access circuits are up. The value configured for the site-preference is propagated between autonomous systems in the BGP VPWS and BGP multihoming update extended community VPLS preference field. The receiving ingress ASBR copies the VPLS preference value into local preference of the update to ensure that the VPLS preference and local preference are equal, which prevents the update from being considered malformed.

In addition to configuring the associated BGP and MPLS infrastructure, the provisioning of a BGP VPWS service requires:

• configuring the BGP Route Distinguisher, Route Target

  The updates are accepted into the service only if they contain the configured import route-target.

• configuring a binding to the pseudowire template

  The multiple pseudowire template bindings can be configured with their associated route-targets used to control which is applied.

• configuring the SAP or static GRE tunnel

• configuring the name of the local VE and its associate VE ID

• configuring the name of the remote VE and its associated VE ID

• for a dual-homed PE:

  • enabling the site

  • configuring the site with non-zero site-preference

• for a remote PE, configure up to two remote VE names and associated VE IDs

• enabling BGP VPWS

The pseudowire template concept used for BGP AD is reused for BGP VPWS to dynamically instantiate pseudowires (SDP-bindings) and the related SDPs (provisioned or automatically instantiated).

The settings for the L2-Info extended community in the BGP update sent by the system are derived from the pw-template attributes. The following rules apply:

• If multiple pw-template-bindings (with or without import-rt) are specified for the VPWS instance, the first (numerically lowest ID) pw-template entry is used.

• Both Ethernet VLAN and Ethernet Raw Mode Encaps Types are supported; these are selected by configuring the vc-type in the pseudowire template to be either vlan or ether, respectively. The default is ether.

  The same value must be used by the remote BGP VPWS instance to ensure that the related pseudowire comes up.

• Layer 2 MTU is derived from the service VPLS service-mtu parameter.

  The same value must be used by the remote BGP VPWS instance to ensure that the related pseudowire comes up.

• Control Flag C can be 0 or 1, depending on the setting of the controlword parameter in the PW template 0.

• Control Flag S is always 0.

On reception, the values of the parameters in the L2-Info extended community of the BGP update are compared with the settings from the corresponding pw-template. The following steps are used to determine the local pw-template:

• The route-target values are matched to determine the pw-template. The binding configured with the first matching route target is chosen.

• If a match is not found from the previous step, the lowest pw-template-binding (numerically) without any route-target configured is used.

• If the values used for encap-type or Layer 2 MTU do not match, the pseudowire is created but with the operationally down state.

  To interoperate with existing implementations, if the received MTU value = 0, the MTU negotiation does not take place; the related pseudowire is set up ignoring the MTU.

• If the value of the S flag is not zero, the pseudowire is not created.

The following pseudowire template parameters are supported when applied within a BGP VPWS service; the remainder are ignored:

configure service pw-template policy-id [use-provisioned-sdp | 
       [prefer-provisioned-sdp] [auto-sdp]] [create] [name name]
   accounting-policy acct-policy-id 
   no accounting-policy
   [no] collect-stats
   [no] controlword
   egress 
      filter ipv6 ipv6-filter-id 
      filter ip ip-filter-id
      filter mac mac-filter-id
      no filter [ip ip-filter-id] [mac mac-filter-id] [ipv6 ipv6-filter-id]
      qos network-policy-id port-redirect-group queue-group-name instance instance
id
      no qos [network-policy-id] 
   [no] force-vlan-vc-forwarding
   hash-label [signal-capability] 
   no hash-label
   ingress 
      filter ipv6 ipv6-filter-id 
      filter ip ip-filter-id
      filter mac mac-filter-id
      no filter [ip ip-filter-id] [mac mac-filter-id] [ipv6 ipv6-filter-id]
      qos network-policy-id fp-redirect-group queue-group-name instance instance-id 
      no qos [network-policy-id]
   [no] sdp-exclude
   [no] sdp-include
   vc-type {ether | vlan}
   vlan-vc-tag vlan-id
   no vlan-vc-tag 

For more information about this command, see the 7450 ESS, 7750 SR, 7950 XRS, and VSR Services Overview Guide.

The use-provisioned-sdp option is permitted when creating the pseudowire template if a preprovisioned SDP is to be used. Preprovisioned SDPs must be configured whenever RSVP-signaled transport tunnels are used.

When the prefer-provisioned-sdp option is specified, if the system finds an existing matching SDP that conforms to any restrictions defined in the pseudowire template (for example, sdp-include or sdp-exclude group), it uses this matching SDP (even if the existing SDP is operationally down); otherwise, it automatically creates an SDP.

When the auto-gre-sdp option is specified, a GRE SDP is automatically created.

The tools perform command can be used in the same way as for BGP-AD to apply changes to the pseudowire template using the following format:

tools perform service [id service-id] eval-pw-template policy-id [allow-service-impact]

If a user configures a service using a pseudowire template with the prefer-provisioned-sdp option, but without provisioning an applicable SDP and the system binds to an automatic SDP, and the user subsequently provisions an appropriate SDP, the system does not automatically switch to the new provisioned SDP. This only occurs if the pseudowire template is reevaluated using the tools perform service id service-id eval-pw-template command.

An endpoint is required on a remote PE connecting to two dual-homed PEs to associate the active/standby pseudowires with the Epipe service. An endpoint is automatically created within the Epipe service such that active/standby pseudowires are associated with that endpoint. The creation of the endpoint occurs when bgp-vpws is enabled (and deleted when it is disabled) and so exists in both a single- and dual-homed scenario. This simplifies converting a single-homed service to a dual-homed service. The naming convention used is _tmnx_BgpVpws-x, where x is the service identifier. The automatically created endpoint has the default parameter values, although all are ignored in a BGP-VPWS service with the description field being defined by the system.

The following command does not have any effect on an automatically created VPWS endpoint:

tools perform service id <service-id> endpoint <endpoint-name> force-switchover

The most basic SDPs must have the following:

• A locally unique SDP identification (ID) number.

• The system IP address of the originating and far-end routers.

• An SDP encapsulation type, either GRE or MPLS.

The Epipe service is designed to carry Ethernet frame payloads, so it can provide connectivity between any two SAPs that pass Ethernet frames. The following SAP encapsulations are supported on the 7450 ESS, 7750 SR, and 7950 XRS Epipe service:

• Ethernet null

• Ethernet dot1q

• QinQ

• SONET/SDH BCP-null for the 7450 ESS and 7750 SR

• SONET/SDH BCP-dot1q for the 7450 ESS and 7750 SR

While different encapsulation types can be used, encapsulation mismatching can occur if the encapsulation behavior is not understood by connecting devices, which are unable to send and receive the expected traffic. For example, if the encapsulation type on one side of the Epipe is dot1q and the other is null, tagged traffic received on the null SAP is double-tagged when it is transmitted out of the dot1q SAP.

One pseudowire encapsulation mode, that is, SDP vc-type, is available: PWE3 N-to-1 Cell Mode Encapsulation.

This section provides a brief overview of the tasks that must be performed and the CLI commands that must be executed to configure the VLL services:

1. Associate the service with a customer ID.

2. Optionally, define SAP parameters:

   • Select egress and ingress QoS and, or scheduler policies (configured in the config>qos context).

   • Select accounting policy (configured in the config>log context).

3. Define spoke-SDP parameters.

4. Enable the service.

This section provides VLL configuration examples for the VLL services.

The control word command provides the option to add a control word as part of the packet encapsulation for PW types for which the control word is optional. These are Ethernet pseudowire (Epipe), ATM N:1 cell mode pseudowires (Apipe vc-types atm-vcc and atm-vpc), and VT pseudowire (Apipe vc-type atm-cell). The control word may be needed because when ECMP is enabled on the network, packets of a specific pseudowire may be spread over multiple ECMP paths if the hashing router mistakes the PW packet payload for an IPv4 or IPv6 packet. This occurs when the first nibble following the service label corresponds to a value of 4 or 6.

The control word negotiation procedures described in Section 6.2 of RFC 4447 are not supported and, therefore, the service only comes up if the same C-bit value is signaled in both directions. If a spoke-SDP is configured to use the control word, but the node receives a label mapping message with a C-bit clear, the node releases the label with an ‟Illegal C-bit” status code per Section 6.1 of RFC 4447. As soon as the user enables control of the remote peer, the remote peer withdraws its original label and sends a label mapping with the C-bit set to 1 and the VLL service is up in both nodes.

When the control word is enabled, VCCV packets also include the VCCV control word. In that case, the VCCV CC type 1 (OAM CW) is signaled in the VCCV parameter in the FEC. If the control word is disabled on the spoke-SDP, the Router Alert label is used. In that case, VCCV CC type 2 is signaled. For a multi-segment pseudowire (MS-PW), the CC type 1 is the only type supported; therefore, the control word must be enabled on the spoke SDP to be able to use VCCV-ping and VCCV-trace.

The following example shows a spoke SDP control word configuration:

-Dut-B>config>service>epipe# info
----------------------------------------------
    description "Default epipe description for service id 2100"
    sap 1/2/7:4 create
        description "Default sap description for service id 2100"
    exit
    spoke-sdp 1:2001 create
        control-word
    exit
    no shutdown
----------------------------------------------
*A:ALA-Dut-B>config>service>epipe#
To disable the control word on spoke-sdp 1:2001:
*A:ALA-Dut-B>config>service>epipe# info
----------------------------------------------
    description "Default epipe description for service id 2100"
    sap 1/2/7:4 create
        description "Default sap description for service id 2100"
    exit
    spoke-sdp 1:2001 create
    exit
    no shutdown
----------------------------------------------
*A:ALA-Dut-B>config>service>epipe#

The following example shows a G.8031 Ethernet tunnel for Epipe protection configuration for 7450 ESS or 7750 SR using same-fate SAPs for each Epipe access (two Ethernet member ports 1/1/1 and 2/1/1/1 are used):

*A:7750_ALU>config>eth-tunnel 1
----------------------------------------------
        description "Protection is APS"
        protection-type 8031_1to1
        ethernet
            mac 00:11:11:11:11:12
            encap-type dot1q
        exit
        ccm-hold-time down 5 up 10 // 50 ms down, 1 second up
        path 1
            member 1/1/1
            control-tag 5 // primary control vlan 5
            precedence primary
            eth-cfm
                mep 2 domain 1 association 1
                    ccm-enable
                    control-mep
                    no shutdown
                exit
            exit
            no shutdown
        exit
        path 2
            member 2/1/1
            control-tag 105 //secondary control vlan 105
            eth-cfm
                mep 2 domain 1 association 2
                    ccm-enable
                    control-mep
                    no shutdown
                exit
            exit
            no shutdown
        exit
        no shutdown
--------------------------------------------------
# Configure Ethernet tunnel SAPs 
--------------------------------------------------
*A:7750_ALU>config>service epipe 10 customer 5 create
        sap eth-tunnel-1 create // Uses control tags from the Ethernet tunnel port
            description "g8031-protected access ctl/data SAP for eth-tunnel 1"

        exit
        no shutdown 
----------------------------------------------
*A:7750_ALU>config>service epipe 11 customer 5 create
    sap eth-tunnel-1:1 create
        description "g8031-protected access same-fate SAP for eth-tunnel 1"

        // must specify tags for each corresponding path in Ethernet tunnel port 
        eth-tunnel path 1 tag 6
        eth-tunnel path 2 tag 106
    exit
    …
----------------------------------------------
*A:7750_ALU>config>service epipe 10 customer 5 create
    sap eth-tunnel-1:3 create
        description "g8031-protected access same-fate SAP for eth-tunnel 1"
        // must specify tags for each path for same-fate SAPs
        eth-tunnel path 1 tag 10
        eth-tunnel path 2 tag 110
    exit
    …
----------------------------------------------

The vc-switching parameter must be specified when the VLL service is created. When the vc-switching parameter is specified, you are configuring an S-PE. This is a pseudowire switching point (switching from one pseudowire to another). Therefore, you cannot add a SAP to the configuration.

The following example shows the configuration when a SAP is added to a pseudowire. The CLI generates an error response if you attempt to create a SAP. VC switching is only needed on the pseudowire at the S-PE.

*A:ALA-701>config>service# epipe 28 customer 1 create vc-switching 
*A:ALA-701>config>service>epipe$ sap 1/1/3 create
MINOR: SVCMGR #1311 SAP is not allowed under PW switching service 
*A:ALA-701>config>service>epipe$

Use the following CLI syntax to create pseudowire switching VLL services. These are examples only. Different routers support different pseudowire switching VLL services.

CLI syntax:

config>service# apipe service-id [customer customer-id] [vpn vpn-id] [vc-type {atm-vcc|atm-sdu|
atm-vpc|atm-cell}] [vc-switching]
description description-string
spoke-sdp sdp-id:vc-id

CLI syntax:

config>service# epipe service-id [customer customer-id] [vpn vpn-id] [vc-switching]
description description-string
spoke-sdp sdp-id:vc-id

CLI syntax:

config>service# fpipe service-id [customer customer-id][vpn vpn-id] [vc-type {fr-dlci}] [vcswitching]
description description-string
spoke-sdp sdp-id:vc-id

CLI syntax:

config>service# ipipe service-id [customer customer-id][vpn vpn-id] [vc-switching] 
description description-string
spoke-sdp sdp-id:vc-id

The following example shows the command usage to configure VLL pseudowire switching services:

config>service# apipe 1 customer 1 vpn 1 vc-switching create
config>service>apipe$ description ‟Default apipe description for service id 100”
config>service>apipe# spoke-sdp 3:1 create
config>service>apipe>spoke-sdp# exit
config>service>apipe# spoke-sdp 6:200 create
config>service>apipe>spoke-sdp# exit
config>service>apipe# no shutdown

The following example shows configurations for each service:

*A:ALA-48>config>service# info
----------------------------------------------
...
	apipe 100 customer 1 vpn 1 vc-switching create
           description "Default apipe description for service id 100"
           spoke-sdp 3:1 create
           exit
           spoke-sdp 6:200 create
           exit
           no shutdown
        exit
...
        epipe 107 customer 1 vpn 107 vc-switching create
            description "Default epipe description for service id 107"
            spoke-sdp 3:8 create
            exit
            spoke-sdp 6:207 create
            exit
            no shutdown
        exit
...
        ipipe 108 customer 1 vpn 108 vc-switching create
            description "Default ipipe description for service id 108"
            spoke-sdp 3:9 create
            exit
            spoke-sdp 6:208 create
            exit
            no shutdown
        exit
...
	 fpipe 109 customer 1 vpn 109 vc-switching create
            description "Default fpipe description for service id 109"
            spoke-sdp 3:5 create
            exit
            spoke-sdp 6:209 create
            exit
            no shutdown
        exit
...
----------------------------------------------
*A:ALA-48>config>service#

VLL resilience shows an example to create VLL resilience. The zero revert-time value means that the VLL path is switched back to the primary immediately after it comes back up.

*A:ALA-48>config>service>epipe# info
----------------------------------------------
            endpoint "x" create
            exit
            endpoint "y" create
            exit
            spoke-sdp 1:100 endpoint "y" create
                precedence primary
            exit
            spoke-sdp 2:200 endpoint "y" create
                precedence 1
            exit
            no shutdown
----------------------------------------------
*A:ALA-48>config>service>epipe#

The following example shows the Cpipe service configuration, supported on the 7750 SR only:

*A:ALA-1>config>service# info
----------------------------------------------
...
        cpipe 94002 customer 1 vc-type cesopsn create
            endpoint "to7705" create
            exit
            endpoint "toMC-APS" create
            exit
            sap aps-4.10.1.2.1 endpoint "toMC-APS" create
                ingress
                    qos 20 
                exit
            exit
            spoke-sdp 14004:94002 endpoint "to7705" create
            exit
            spoke-sdp 100:294002 endpoint "toMC-APS" icb create
            exit
            spoke-sdp 100:194002 endpoint "to7705" icb create
            exit
            no shutdown
        exit
...
----------------------------------------------
*A:ALA-1>config>service> Cpipe#

A Cpipe service cannot be deleted until SAPs are shut down and deleted. If a spoke-SDP is defined, it must be shut down and removed from the configuration as well.

Use the following CLI syntax to delete a Cpipe service.

CLI syntax:

config>service#
[no] cpipe service-id [customer customer-id]
   [no] spoke-sdp sdp-id 
      [no] shutdown
   shutdown

The following example shows how to add an accounting policy to an existing SAP:

config>service# epipe 2 
config>service>epipe# sap 2/1/3:21
config>service>epipe>sap# accounting-policy 14
config>service>epipe>sap# exit

The following example shows the SAP configuration:

ALA-1>config>service# info
----------------------------------------------
    epipe 2 customer 6 vpn 2 create
            description "Distributed Epipe service to east coast"
            sap 2/1/3:21 create
              accounting-policy 14
            exit
            spoke-sdp 2:6000 create
            exit
            no shutdown
        exit
----------------------------------------------
ALA-1>config>service#

You can shut down an Epipe service without deleting the service parameters.

CLI syntax:

config>service> epipe service-id 
shutdown

Example:

config>service# epipe 2
config>service>epipe# shutdown
config>service>epipe# exit

Use the following CLI syntax to re-enable an Epipe service that was shut down.

CLI syntax:

config>service# epipe service-id 
no shutdown

Example:

config>service# epipe 2
config>service>epipe# no shutdown
config>service>epipe# exit

The following example shows the command usage to modify Ipipe parameters, supported on the 7450 ESS and 7750 SR only.

Example:

config>service# ipipe 202
config>service>ipipe# sap 1/1/2:444
config>service>ipipe>sap# shutdown
config>service>ipipe>sap# exit
config>service>ipipe# no sap 1/1/2:444
config>service>ipipe# sap 1/1/2:555 create
config>service>ipipe>sap$ description ‟eth_ipipe”
config>service>ipipe>sap$ ce-address 10.31.31.1
config>service>ipipe>sap$ no shutdown
config>service>ipipe>sap$ exit
config>service>ipipe# info

A:ALA-48>config>service# info
----------------------------------------------
...
        ipipe 202 customer 1 create
            sap 1/1/2:445 create
                description "eth_ipipe"
                ce-address 10.31.31.2
            exit
            sap 1/1/2:555 create
                description "eth_ipipe"
                ce-address 10.31.31.1
            exit
            no shutdown
        exit
...
----------------------------------------------
A:ALA-48>config>service#

An Ipipe service can be shut down without deleting any service parameters.

CLI syntax:

config>service#
ipipe service-id
  shutdown

Example:

A:ALA-41>config>service# ipipe 202
A:ALA-41>config>service>ipipe# shutdown

A:ALA-48>config>service# info
----------------------------------------------
...
       ipipe 202 customer 1 create
           shutdown
           sap 1/1/2:445 create
               description "eth_ipipe"
               ce-address 10.31.31.2
           exit
           sap 1/1/2:555 create
               description "eth_ipipe"
               ce-address 10.31.31.1
           exit
       exit
...
----------------------------------------------
A:ALA-48>config>service#

Use the following CLI syntax to re-enable an Ipipe service that was shut down.

CLI syntax:

config>service#
ipipe service-id 
   no shutdown

Example:

A:ALA-41>config>service# ipipe 202
A:ALA-41>config>service>ipipe# no shutdown

An Ipipe service cannot be deleted until the SAP is shut down. If protocols and, or a spoke-SDP are defined, they must be shut down and removed from the configuration as well.

Use the following CLI syntax to delete an Ipipe service.

CLI syntax:

config>service#
    — no ipipe service-id 
        — shutdown
        — no sap sap-id
            — shutdown
        — no spoke-sdp [sdp-id:vc-id]
            — shutdown

Example:

config>service# ipipe 207
config>service>ipipe# sap 1/1/2:449
config>service>ipipe>sap# shutdown
config>service>ipipe>sap# exit
config>service>ipipe# no sap 1/1/2:449
config>service>ipipe# spoke-sdp 16:516
config>service>ipipe>spoke-sdp# shutdown
config>service>ipipe>spoke-sdp# exit
config>service>ipipe# no spoke-sdp 16:516
config>service>ipipe# exit
config>service# no ipipe 207
config>service#