The SR OS LDP IPv6 implementation uses a 128-bit LSR-ID as defined in draft-pdutta-mpls-ldp-v2-00. See LDP Process Overview for more information about interoperability of this implementation with 32-bit LSR-ID, as defined in RFC 7552.
Hello adjacency is brought up using link Hello packet with source IP address set to the interface link-local unicast address and a destination IP address set to the link-local multicast address FF02:0:0:0:0:0:0:2.
The transport address for the TCP connection, which is encoded in the Hello packet, is set to the LSR-ID of the LSR by default. It is set to the interface IPv6 address if the user enabled the interface option under one of the following contexts:
The interface global unicast address, meaning the primary IPv6 unicast address of the interface, is used.
The user can configure the local-lsr-id option on the interface and change the value of the LSR-ID to either the local interface or to another interface name, loopback or not. The global unicast IPv6 address corresponding to the primary IPv6 address of the interface is used as the LSR-ID. If the user invokes an interface which does not have a global unicast IPv6 address in the configuration of the transport address or the configuration of the local-lsr-id option, the session does not come up and an error message is displayed.
The LSR with the highest transport address bootstraps the IPv6 TCP connection and IPv6 LDP session.
Source and destination addresses of LDP/TCP session packets are the IPv6 transport addresses.