Introduction
I showed how to use MPLS transport tunnel signalling protocols such as LDP and RSVP-TE to establish Underlay MPLS tunnels to carry Overlay network services such as ePipe, VPLS and VPRN (L3VPN) for Nokia, Cisco and Juniper routers in my earlier articles. RSVP-TE offers Traffic Engineering (TE) capability where path of each LSP can be manually defined hop-by-hop or signalled based on meeting certain QoS requirements instead of just following the IGP’s shortest path as in the case of LDP. TE allows a carrier to maximize its network resource utilization beyond IGP’s shortest paths that sometime overloads certain shortest-path links while other links are being idled and are only used during network failure fall over.
While many carriers have been quite successful in consolidating their legacy networks such as TDM, ATM, Frame Relay, and IP into a single IP/MPLS QoS-ready network in the past decade and use the IP/MPLS QoS-ready platform to offer new network services, many carriers find themselves running both non-TE LDP and RSVP-TE transport tunnel signalling protocols in their MPLS networks. This is because while RSVP-TE offers Underlay network TE LSP signalling capability, the protocol generates too many LSP soft-state refresh messages and every router along a RSVP-TE signalled TE LSP or network path needs to store some RSVP-TE state…
