The SR OS implementation provides the option for configuring and encoding a 32-bit LSR-ID in the LDP IPv6 Hello message to achieve interoperability in deployments strictly adhering to RFC 7552.
The LSR-ID of an LDP Label Switched Router (LSR) is a 32-bit integer used to uniquely identify it in a network. SR OS also supports LDP IPv6 in both the control plane and data plane. However, the implementation uses a 128-bit LSR-ID, as defined in draft-pdutta-mpls-ldp-v2 to establish an LDP IPv6 Hello adjacency and session with a peer LSR.
The SR OS LDP IPv6 implementation complies with the control plane procedures defined in RFC 7552 for establishing an LDP IPv6 Hello adjacency and LDP session. However, the SR OS LDP IPv6 implementation does not interoperate with third-party implementations of this standard, because the latter encode a 32-bit LSR-ID in the IPv6 Hello message, while SR OS encodes a 128-bit LSR-ID.
When this feature is enabled, an SR OS LSR is able to establish an LDP IPv6 Hello adjacency and an LDP IPv6 session with an RFC 7552 compliant peer or targeted peer LSR, using a 32-bit LSR-ID and a 128-bit transport address.