RSVP-TE TE++ LDP Tunneling

The LSPs established by LDP are tunneled through the LSPs established by RSVP. LDP effectively treats the traffic-engineered LSPs as single hops. If you enable LDP tunneling across RSVP-established LSPs, LDP automatically establishes the session with the router at the other end of the RSVP LSP. An RVSP-assigned label is automatically added to the label stack of the packets with LDP-assigned labels, and packets are pushed through the RSVP LSP. However, LDP control packets are routed hop-by-hop, rather than carried through the LSP. This routing allows you to use simplex (one-way) traffic-engineered LSPs. Traffic in the opposite direction flows through LDP-established LSPs that follow unicast routing rather than through traffic-engineered tunnels, unless LDP tunneling over RSVP is enabled in the opposite direction, too. This feature enables support for LDP tunneling over container LSPs in an RSVP-TE TE++ architecture.