The purpose of this object is to uniquely identity a
tunnel within a network. When the MPLS signalling
protoocol is rsvp(2) this value SHOULD mimic the
Extended Tunnel Id field in the SESSION object.
When the MPLS signalling protoocol is crldp(3) this
value SHOULD mimic the Ingress LSR Router ID field
in the LSPID TLV object.