SRv6 Epipe services

Epipe services support SRv6 End.DX2 behavior. Currently, the SRv6 SID for End.DX2 is signaled by EVPN-VPWS AD per-EVI routes.

The following CLI configures an Epipe service for SRv6:

+--epipe
   +--segment-routing-v6 <instance-id> 
   |  +--locator <locator-name>  
   |  |  +--function 
   |  |  |  +--end-dx2 <integer>
   |  +--bgp-evpn
   |  |  +-- segment-routing-v6 <number>
   |  |  |   +-- admin-state <keyword>
   |  |  |   +-- default-route-tag <number>
   |  |  |   +-- ecmp <number>
   |  |  |   +-- force-vc-forwarding <keyword>
   |  |  |   +-- oper-group <reference>
   |  |  |   +-- route-next-hop
   |  |  |   |   +-- ip-address <ip-address>
   |  |  |   |   +-- system-ipv4
   |  |  |   |   +-- system-ipv6
   |  |  |   +-- source-address <global-unicast-ipv6-address>
   |  |  |   +-- srv6
   |  |  |       +-- default-locator <reference>
   |  |  |       +-- instance <reference>

Where the following conditions apply:

The SRv6 Epipe is configured with the locator that is used. This determines the SID structure and value that is advertised in the AD per EVI route for the service.
A single SRv6 instance with a single locator is supported on Epipes.
The SRv6 Epipe uses an End.DX2 function value that, if not configured, is dynamically allocated by the system, out of the dynamic range available for the locator. If the end-dx2 function is configured, then this value is used instead of a dynamic value.
The following is supported in SRv6 Epipes:

ecmp

used for aliasing on remote SRv6 EVPN ES destinations

force-vlan-vc-forwarding

used to preserve one VLAN tag in the payload of the SRv6 tunnel. On termination, the VLAN tag is transparently passed through the termination SRv6 FPE.

default-route-tag

used to allow easy matching of the service routes on export policies

oper-group

required for fault-propagation and fate-sharing with the monitoring objects

route-next-hop

required to control the advertised BGP next hop for the EVPN AD per-EVI route. When EVPN Multi-homing is used, this value must match the ES originating-ip and the ES route-next-hop value.

EVPN-VPWS is the control plane technology to signal SRv6 Epipes. The local-attachment-circuit Ethernet-tag value is advertised in an AD per-EVI route that may have a zero or non-zero ESI (if multi-homing is used). The AD per-EVI routes are advertised along with the Layer-2 SRv6 Services TLV encoding with an End.DX2 behavior and using the transposition procedures described in Transposition procedures when advertising service routes. Upon reception the ingress PE creates an EVPN destination, as long as the received route includes the remote expected Ethernet-tag and route-target. The following CLI excerpt shows a configuration example and the created EVPN SRv6 destination on the PE:

*A:PE-3# configure service epipe 200 
*A:PE-3>config>service>epipe# info 
----------------------------------------------
            segment-routing-v6 1 create
                locator "LOC-1"
                    function
                        end-dx2 200
                    exit
                exit
            exit
            bgp
            exit
            bgp-evpn
                local-attachment-circuit ac-23 create
                    eth-tag 23
                exit
                remote-attachment-circuit ac-5 create
                    eth-tag 5
                exit
                evi 200
                segment-routing-v6 bgp 1 srv6-instance 1 default-locator "LOC-1" create
                    source-address 2001:db8::3
                    ecmp 2
                    route-next-hop system-ipv6
                    no shutdown
                exit
            exit
            sap lag-1:200 create
                no shutdown
            exit
            no shutdown
----------------------------------------------
*A:PE-3>config>service>epipe# /show service id 200 segment-routing-v6 destinations 

===============================================================================
TEP, SID
===============================================================================
Instance  TEP Address                        Segment Id
-------------------------------------------------------------------------------
1         2001:db8::5                        cafe:1:0:5:c:8000::
-------------------------------------------------------------------------------
Number of TEP, SID: 1
-------------------------------------------------------------------------------
===============================================================================

===============================================================================
Segment Routing v6 Ethernet Segment Dest
===============================================================================
Instance  Eth SegId                       Num. Macs     Last Change
-------------------------------------------------------------------------------
No Matching Entries
===============================================================================

SRv6 Epipes support EVPN Multi-homing. Their associated Ethernet Segments (ES) can be shared among MPLS services and other SRv6 services.

EVPN Multi-homing for SRv6 Epipes follows these guidelines:

The ES used by SRv6 Epipes is only supported in evi-rt mode, therefore separate AD per-ES routes per service are advertised for SRv6 Epipes.
If evi-rt-set is configured in the ES, the SRv6 services are skipped when packing route-targets for the AD per-ES route. This is the same behavior as having a Epipe services with a configured vsi-export policy; the system also skips the route-targets for Epipes with vsi-export when packing multiple route-targets in the same AD per-ES route.

The advertised AD per-ES route for the SRv6 Epipe includes a Layer-2 SRv6 Services TLV with a SID value of zero. The used behavior code point is End.DT2M. In addition, the AD per-ES route is also advertised with an ESI Label extended community that encodes the implicit-null value in the ESI label field. A debug example of a received AD per-ES route for SRv6 follows:

22 2021/05/21 18:23:10.247 UTC MINOR: DEBUG #2001 Base Peer 1: 2001:db8::2
"Peer 1: 2001:db8::2: UPDATE
Peer 1: 2001:db8::2 - Received BGP UPDATE:
    Withdrawn Length = 0
    Total Path Attr Length = 125
    Flag: 0x90 Type: 14 Len: 48 Multiprotocol Reachable NLRI:
        Address Family EVPN
        NextHop len 16 Global NextHop 2001:db8::2
        Type: EVPN-AD Len: 25 RD: 192.0.2.2:200 ESI: 01:d8:47:ff:00:00:00:00:01:
00, tag: MAX-ET Label: 0 
    Flag: 0x40 Type: 1 Len: 1 Origin: 0
    Flag: 0x40 Type: 2 Len: 0 AS Path:
    Flag: 0x40 Type: 5 Len: 4 Local Preference: 100
    Flag: 0xc0 Type: 16 Len: 16 Extended Community:
        target:64500:200
        esi-label:3/Single-Active
    Flag: 0xc0 Type: 40 Len: 37 Prefix-SID-attr:
       SRv6 Services TLV (37 bytes):-
         Type: SRV6 L2 Service TLV (6)
         Length: 34 bytes, Reserved: 0x0
         SRv6 Service Information
         Service Information Sub-TLV Type 1
            Type: 1 Len: 30 Rsvd1: 0x0
            SRv6 SID: ::
            SID Flags: 0x0 Endpoint Behavior: 0x18 Rsvd2: 0x0
            SRv6 SID Sub-Sub-TLV
               Type: 1 Len: 6
               BL:0 NL:0 FL:0 AL0 TL:0 TO:0

The creation of ES destinations follows the same rules as in EVPN-VPWS services with MPLS transport, except that the ES destination is resolved to remote SRv6 SIDs, as shown in the following example:

*A:PE-5# show service id 200 segment-routing-v6 destinations 

===============================================================================
TEP, SID
===============================================================================
Instance  TEP Address                        Segment Id
-------------------------------------------------------------------------------
No Matching Entries
===============================================================================

===============================================================================
Segment Routing v6 Ethernet Segment Dest
===============================================================================
Instance  Eth SegId                       Num. Macs     Last Change
-------------------------------------------------------------------------------
1         01:d8:47:ff:00:00:00:00:01:00   0             06/18/2021 17:04:15
-------------------------------------------------------------------------------
Number of entries: 1
-------------------------------------------------------------------------------
===============================================================================
*A:PE-5# show service id 200 segment-routing-v6 esi 01:d8:47:ff:00:00:00:00:01:00 

===============================================================================
Segment Routing v6 Ethernet Segment Dest
===============================================================================
Instance  Eth SegId                       Num. Macs     Last Change
-------------------------------------------------------------------------------
1         01:d8:47:ff:00:00:00:00:01:00   0             06/18/2021 17:04:15
-------------------------------------------------------------------------------
Number of entries: 1
-------------------------------------------------------------------------------
===============================================================================

===============================================================================
Segment Routing v6 Dest TEP Info
===============================================================================
Instance  TEP Address                   Segment Id          Last Change
-------------------------------------------------------------------------------
1         2001:db8::2                   cafe:1:0:2:c:8000:: 06/18/2021 17:04:15
-------------------------------------------------------------------------------
Number of entries : 1
-------------------------------------------------------------------------------
===============================================================================