Identifies the ingress LSR ID of the primary tunnel.
When the MPLS signalling protocol is rsvp(2),LSR ID
equals to the Tunnel Sender Address in the Sender
Template object or the Extended Tunnel Id in the
SESSION object. When the MPLS signalling protocol is
crldp(3), LSR ID equals to the Ingress
LSR Router ID in the LSPID TLV object.