A tag-switching router on a tag-switching network establishing a single
tag distribution protocol (TDP) session with a peer for the advertisement
of tag bindings shared by two or more interfaces and contemporaneously
establishing with the peer one or more additional TDP sessions for the
advertisement of tag bindings dedicated for use by specific interfaces.
Each router interface has an assigned tag space comprised incoming tags
that are appended by the peer to input data packets forwarded by the
peer. A new Hello message carried in a TDP protocol data unit (PDU) is
introduced for use in a TDP discovery mechanism. The router periodically
multicasts a specific Hello message from each tag-switching enabled
interface and a router TDP identifier in the TDP PDU header identifies
the tag space that the router has assigned to the interface. When the
router receives a Hello message from the peer at one of its interfaces,
the router records the peer TDP identifier in a record associated with
the interface to create a link adjacency. The router and peer establish a
conventional TDP session to exchange tag binding sets. The router
transmits to the peer a Bind message containing advertised tag bindings
which, in turn, contain the incoming tags for the tag space identified by
the router TDP identifier in the TDP PDU header. The router receives from
the peer a Bind message from the peer containing learned tag bindings
which, in turn, contain the outgoing tags for the tag space identified by
the peer TDP identifier in the TDP PDU header. The router appends
outgoing tags to received data packets having destination addresses bound
to the learned tag bindings and forwards the tagged received data packets
to the peer from the associated interface.