SDP help

[moods]

I am reading NSR2 self-study guide and having hard times with SDP.

It`s described as the transport tunnel for the distributed service. The configuration is clear, but I guess that I do not totally understand the concept.(Cisco does not have this)

a.) Is it required only for distributed L2 services? (signaling of the service labels and define the transport to the remote node)

· Can we have operational VPLS without SDP? Manually created T-LDP (for signaling of service labels) + LDP/LSP for transport labels?


b.) I saw that can be used with L3 services too. I do not understand why? MP-BGP advertise the service labels and mpls is configured on “core” network.

Thanks for clarification

[mivens]

Think of it less as signalling for the labels and more for the technology used for the encapsulation/tunnelling of the traffic.

As you pointed out, you can use MPLS to transport traffic for a VPN service across a network. But another way you could do it, for example, could be to use a GRE tunnel. In Alcatel-speak, in that case you would be using an GRE SDP rather than an MPLS SDP for your service.

An SDP abstracts that transport used for the service from the rest of the configuration.