VLL services

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 more information about 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 received frame. 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:

  • multisegment pseudowires

  • 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 or to set the QoS information, or both, 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 is operationally down, the Epipe service that contains that connection is also operationally down. The user can configure a single SAP within an Epipe without affecting 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 remains up; it does not transition to down. The SAP remains 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 the E-NNI peer is shutdown in such a way that it causes the SAP to become operationally down.

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 on a SAP configured on a LAG that has no ports.

The VLL Connection Admission Control (CAC) is supported for the 7705 SAR Gen 2 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 datapath 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 multichassis 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.

Cpipe service is the Nokia implementation of TDM PW VLL as defined in the IETF PWE3 working group.

The 7705 SAR Gen 2 supports TDM circuit applications that transport delay-sensitive TDM traffic over a packet network. For example, in the case of cell site aggregation, Cpipe services provide transport service for 2G connectivity between the base transceiver station and the base station controller, and for 3G backhaul applications (for example, EVDO traffic from T1/E1 ports with MLPPP). Cpipe services over MPLS or GRE tunnels are supported.

The legacy TDM traffic is transported encapsulated in a TDM VLL over the packet-switched network (PSN). The entire T1/E1 frame or part of a frame (n ✕ 64 kb/s) is carried as a TDM VLL over the PSN. At the far end, the transport layer frame structure is regenerated when structured circuit emulation is used, or simply forwarded as part of the payload when unstructured circuit emulation is used.

TDM VLLs can be configured with both endpoints (SAPs) on the same 7705 SAR Gen 2. This is referred to as TDM SAP-to-SAP or local TDM service. TDM SAP-to-SAP emulates a TDM multiplexing and switching function on the 7705 SAR Gen 2.

A TDM SAP-to-SAP connection is set up in the 7705 SAR Gen 2 and a pseudowire is configured between the two endpoints.

Cpipe services support structured circuit emulation mode (CESoPSN) for n ✕ 64 kb/s timeslots in DS1 and E1 circuits, as described in RFC 5086.

The following figure shows the format of the CESoPSN TDM payload (with and without CAS) for packets carrying trunk-specific n ✕ 64 kb/s service.

For CESoPSN without CAS, select the packet size so that an integer number of frames are transported. That is, if n timeslots per frame are to be encapsulated in a TDM PW, the packet size must be a multiple of n (where n is not equal to 1). For example, if n = 4 timeslots, the packet size can be 8, 12, 16, and so on. If only one timeslot per frame is being transported, the packet size must be an even number.

For CESoPSN with CAS, the packet size is an integer number of frames. A single T1/E1 port can have a mix of CAS and non-CAS traffic in each DS0/64 kb/s channel. You must configure the relevant T1/E1 port or channel group for CAS signal mode before provisioning the TDM PW with CAS, or the system will disallow the signal mode configuration. The extra bytes for ABCD (CAS) signaling bits are not included when setting the packet size.

For a single T1/E1 port that contains a mix of CAS and non-CAS signaling, all non-CAS channel Cpipes inherit the CAS channel restriction on 24/16 frames payload size. For a T1 port, the payload size is equal to the number of CAS and/or non-CAS timeslots ✕ 24 frames/multiframe ✕ n multiframes, where n = 1 to 8. For an E1 port, the payload size is equal to the number of CAS and/or non-CAS timeslots ✕ 16 frames/multiframe ✕ n multiframes, where n =1 to 8.

E1 circuits as defined in RFC 4553, and structured circuit emulation mode (CESoPSN) for n ✕ 64 kb/s timeslots in DS1 and E1 circuits as defined in RFC 5086.

The following table lists the adapter cards, modules, and chassis that support CESoPSN.

The CE-bound interworking function (IWF) uses the sequence numbers in the control word to detect lost and incorrectly ordered packets. Incorrectly ordered packets that cannot be reordered are discarded.

For unstructured CES, the payload of received packets with the L bit set is replaced with an all-ones pattern. For structured CES, the payload of received packets with the L bit set is replaced with an all-ones or a user-configurable bit pattern. This is configured using the idle-payload-fill command. For structured CES with CAS, the signaling bits are replaced with an all-ones or a user-configurable bit pattern.

All circuit emulation services can have a status of up, loss of packets (LOP), or admin down, and any jitter buffer overruns or underruns are logged.

Transparent SDH/SONET over packet (TSoP) is a method for transporting clear channel OC3/STM1 or clear channel OC12/STM4 traffic over a packet network using OC3/STM1 TSoP SFPs and OC12/STM4 TSoP SFPs. With TSoP, the entire signal is encapsulated in a pseudowire and transported over the network to a single destination, which simplifies operation. TSoP is modeled after the SAToP method for pseudowire transport of DS1, E1, DS3, or E3 circuits (RFC 4553).

TSoP SFPs are inserted into Ethernet SFP ports, and the 7705 SAR Gen 2 treats them as standard Ethernet SFPs. To set up the TSoP service, an Epipe must be created across the network connecting two OC3/STM1 TSoP SFPs or two OC12/STM4 TSoP SFPs. The TSoP SFPs implement DCR for service clock delivery. Both nodes must be synchronized against a common clock for DCR.

TSoP SFPs are supported on the 7705 SAR-Hx and 7705 SAR-Mx.

To implement pseudowire redundancy, a VLL service accommodates more than a single object on the SAP side and on the spoke-SDP side.

The following figure 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, create up to two explicitly named endpoints per VLL service. The endpoint name is locally significant to the VLL service. In the preceding figure, endpoints are referred to as endpoint X and endpoint Y.

In the preceding figure, endpoint Y can also have a SAP 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 only 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 only one primary spoke-SDP per VLL endpoint is supported.

• secondary spoke-SDP

  A maximum of four secondary spoke-SDPs per endpoint are supported. 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. At the time this endpoint object is created, the user must explicitly indicate that the spoke-SDP is an ICB; however, a few scenarios are possible where the user can configure the spoke-SDP as an ICB or as a regular spoke-SDP on a specified node. The CLI for those cases indicate both options.

A VLL service endpoint can use only 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 the ICB spoke-SDP type 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 include 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 a VLL service with endpoints. Any allowed combination of objects, as specified in Redundant VLL service model, can be used on endpoints X and Y.

This section uses the specific combination of objects shown in Redundant VLL endpoint objects as an example to describe the more general rules.

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 figure 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 designated forwarder (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 DF 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 the 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 VPLS 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, configuring 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 control-word 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 7705 SAR Gen 2 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 include 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 section describes encapsulations and PW types for VLL services.

When applied to Epipe services, service ingress QoS policies only create the unicast queues defined in the policy. The multipoint queues are not created on the service.

With Epipe services, egress QoS policies function as with other services where the class-based queues are created as defined in the policy. Both Layer 2 or Layer 3 criteria can be used in the QoS policies for traffic classification in a service.

Epipe and Ipipe services can have a single filter policy associated on both ingress and egress. Both MAC and IP filter policies can be used on Epipe services.

Epipe services are point-to-point Layer 2 VPNs capable of carrying any Ethernet payloads. Although an Epipe is a Layer 2 service, the 7705 SAR Gen 2 Epipe implementation does not perform any MAC learning on the service, so Epipe services do not consume any MAC hardware resources.

The PW control word (CW) is a 32-bit field that is inserted between the VC label and the Layer 2 frame. The presence of the control word is indicated by the C bit of the FEC element used in LDP signaling. The PW control word is described in RFC 4385.

The PW control word is supported for all implemented PW types:

• Epipes (Ethernet VLLs)

• Cpipes (TDM VLLs in CESoPSN circulation emulation mode)

For Epipes (except MEF 8 services), the control word is optional. If it is enabled, it will be set to all zeros and ignored on egress.

For Cpipes and Epipe MEF 8 services, the control word is mandatory and cannot be configured.

When the packet length is less than 64 bytes (that is, the length of the Layer 2 payload plus the length of the control word), the length field in the control word is set to the length of the packet. Otherwise, the length field is set to 0. The CE-bound PE uses the length field in the control word to determine the size of padding added by the PSN, so that the PE can extract the PW payload from the PW packet. If the control word is not set for packets less than 64 bytes, the PE cannot determine the original packet length and forwards the payload, including the padding bits. When the CE receives the padded packet, the packet is dropped.

The following points describe the behavior of the 7705 SAR Gen 2 when it receives a Label Mapping message for a PW. It is assumed that no Label Mapping message for the PW has been sent to the next PW router yet. The 7705 SAR Gen 2 operating system performs the following:

• If the received Label Mapping message has C = 0 (where C refers to the C bit of the FEC element), a Label Mapping message with C = 0 is sent forward to the next router (or hop). In this case, the control word is not used.

• If the received Label Mapping message has C = 1 and the PW is locally configured such that the use of the control word is mandatory, the 7705 SAR Gen 2 sends a Label Mapping message with C = 1. In this case, the control word is used.
  Note: : CESoPSN (Cpipes) and Epipe MEF 8 services always require the control word.

• If the received Label Mapping message has C = 1 and the PW is locally configured such that the use of the control word is not supported, the 7705 SAR Gen 2 sends a new Label Mapping message in which the C bit is set to correspond to the locally configured preference for use of the control word (that is, C = 0).

Pseudowire (PW) redundancy protects a PW and any services on the PW against endpoint failures. This differs from LSP redundancy and FRR, which offer protection against link and node failures within the backhaul network.

As shown in Pseudowire redundancy, to provide redundant PWs, the 7705 SAR Gen 2 must signal PWs to two endpoints at the MTSO (7x50-1 and 7x50-2), which is done using two spoke SDPs on the 7705 SAR Gen 2. This configuration removes any single point of failure from a particular network. If 7x50-1 loses all of its connectivity to the network or to the RNC, the 7705 SAR Gen 2 can reroute the PW traffic to 7x50-2, which switches traffic to the RNC.

For end-to-end protection, PW redundancy is supported in the following scenarios:

• PW redundancy with multichassis LAG (MC-LAG)

• PW redundancy with VPLS or PW switching (for Epipes)

PW redundancy applies to all VLL services available on the 7705 SAR Gen 2: Cpipe and Epipe.

Pseudowire redundancy, as described in the previous section, operates in active/active mode. That is, the primary pseudowire is up and ready to transmit and receive traffic, and the secondary pseudowire is up and ready to receive traffic. In the following figure, if both pseudowires were active, this mode of operation would offer seamless redundancy in most cases. However, this mode could also potentially stress the IGP; for example, in active/active mode, the number of advertised routes is greater than in active/standby mode. Another example is the duplication of Ethernet control frames to the 7705 SAR Gen 2 from a VPLS or VPRN service on an 7750 SR node through both primary and secondary VLLs.

Active/standby mode, also called standby signaling, is introduced to address these issues. Standby signaling is supported on all VLLs: Cpipes and Epipes

Standby signaling has two components: standby-signaling master and standby-signaling slave.

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

1. Associate the service with a customer ID.

2. Define SAP parameters.

   • Optional - select egress and ingress QoS or scheduler policies, or both (configured in the config>qos context).

   • Optional - 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. It can be enabled for Ethernet PW (Epipe). The control word may be needed because, when ECMP is enabled on the network, packets of a specific PW 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 comes up only 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 multisegment 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 using same-fate SAPs for each Epipe access (two Ethernet member ports 1/1/1 and 2/1/1/1 are used):

*A:node-2>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:node-2>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:node-2>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:node-2>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# epipe service-id [customer customer-id] [vpn vpn-id] [vc-switching]
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 configurations for each service:

*A:ALA-48>config>service# info
----------------------------------------------
...

        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
...

The following figure 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.

PE-1

The following example shows the configuration on PE-1:

*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 figure shows an example of VLL resilience with pseudowire switching.

T-PE-1

The following example shows the configuration on T-PE-1.

*A:ALA-48>config>service>epipe# info
----------------------------------------------
            endpoint "x" create
            exit
            endpoint "y" create
            exit
            sap 1/1/1:100 endpoint "x" create
            exit
            spoke-sdp 1:100 endpoint "y" create
                precedence primary
            exit
            spoke-sdp 2:200 endpoint "y" create
                precedence 1
            exit
            spoke-sdp 3:300 endpoint "y" create
                precedence 1
            exit
            no shutdown
----------------------------------------------
*A:ALA-48>config>service>epipe#

T-PE-2

The following is an example configuration output on T-PE-2.

*A:ALA-49>config>service>epipe# info
----------------------------------------------
            endpoint "x" create
            exit
            endpoint "y" create
                revert-time 100
            exit
            spoke-sdp 4:400 endpoint "y" create
                precedence primary
            exit
            spoke-sdp 5:500 endpoint "y" create
                precedence 1
            exit
            spoke-sdp 6:600 endpoint "y" create
                precedence 1
            exit
            no shutdown
----------------------------------------------
*A:ALA-49>config>service>epipe#

S-PE-1

The following is an example configuration output on S-PE-1.

*A:ALA-50>config>service>epipe# info
----------------------------------------------
...
            spoke-sdp 1:100 create
            exit
            spoke-sdp 4:400 create
            exit
            no shutdown
----------------------------------------------
*A:ALA-49>config>service>epipe#

Use the following command to add an accounting policy to an existing SAP.

configure service epipe sap accounting-policy

The following example displays an accounting policy configuration.

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

Use the following command to shut down an Epipe service without deleting the service parameters.

configure service epipe service-id shutdown

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

configure service epipe service-id no shutdown