Binding SID (BSID) for Static SRv6 TE Tunnels

The SRv6 binding SID (BSID) helps isolate or decouple different source-routed domains, improving network scalability. The BSID allows the seggregation of the network into multiple TE tunnels, each comprising its own stack, backup paths, and compute model. This feature introduces the allocation of SRv6 BSID under SRv6 TE tunnel.

With the ingress SRv6-TE feature a service payload is encapsulated in an IPv6 tunnel with an SRH that directs the traffic to take a specific TE path in the network. This SID stack can grow in size thereby increasing the overhead of the packet. Some devices in the network might not support such big stacks in incoming packets. In addition to this, it is impractical to encode the whole stack in the ingress node in inter-domain networks. Encoding the whole stack might result in a very heavy TE database and might also cause convergence issues. If there is a transit MPLS domain, then the labels and SRv6 SIDs might result in too much of an overhead.

The SRv6 binding SID provides a solution to this increasing overhead of a packet. With this feature, you can allocate SRv6 binding SID under an SRv6-TE tunnel. The ingress node only requires a subset of TE database of other domains. The convergence is taken care of at transit nodes that are provisioned with the binding SID resulting in a comparitively reduced size stack at the ingress node. You can further reduce the stack size with micro SRv6 SID compression.

The SRv6 binding supports both classic and micro SIDs:

• Classic SRv6 binding SID: This is a variation of the END behaviour of classic SIDs, where the Endpoint is bound to an SRv6 policy with encapsulation.

  • END.B6.Encaps

    This is a non-reduced mode implementation and thus the outer IPv6 encap’s destination address is in the SRH.

    A transit node configured with the binding SID receives an incoming packet with its destination address matching the END.B6.Encaps through longest prefix match and encapsulates the outgoing packet with an SRH.
  • END.B6.Encaps.Red

    Endpoint is bound to an SRv6 policy with reduced SRH encapsulation. There may or may not be an SRH for the outer IPv6 Encap. The outer IPv6 Encap’s destination address is not added to the SRH.

• Micro SRv6 Binding SID

  This is a variation of the END behaviour of micro SIDS, where the Endpoint is bound to an SRv6 policy with encapsulation.

  • END.B6.Encaps with Next-C-SID

    This is a non-reduced mode implementation for micro SIDs and thus the outer IPv6 encap’s destination address is in the SRH of the micro SID.

  • END.B6.Encaps.Red with Next-C-SID Endpoint is bound to an SRv6 policy with reduced SRH encapsulation for micro SIDs. There may or may not be an SRH for the outer IPv6 Encap. The outer IPv6 Encap’s destination address is not added to the SRH of micro SIDs.

To enable transit functionality of a static SRv6 TE tunnel through SRv6 Binding SID:

• For classic SIDS, include the srv6-binding-sid statement at the [edit protocols source-packet-routing source-routing-path] hierarchy level.

• For micro SIDS, the micro-srv6-binding-sid statement at the [edit protocols source-packet-routing source-routing-path] hierarchy level.