MPLS TE Fast ReRoute

pc_varanda · ‎06-12-2012

Hi Experts,

I'm just getting started with MPLS TE and wondering on how fast the "fast reroute" feature can be.

I'm planning to create two tunnels for a specific traffic of my network, and looks like MPLS TE with FRR is the most reliable option if we are talking about a really 0% packet loss network.

I saw on some documentations that with MPLS TE is possible to reroute the traffic with 50 ms of RTT and no packet loss at all, considering that the backup tunnel is so reliable as the primary is.

Is this true? I'm new on this subject so I would like to know more about what I could achieve in terms of high availability.

Regards

Paulo Varanda

narainarun · ‎06-13-2012

Hi,

Yes MPLS-TE with FRR gives faster convergence in range of 50ms (usually 50ms is standard convergence time for SDH/Sonet network). But there are some pre-requisities for MPLS-TE FRR to provide that faster convergence.

Tunnel Headend -- Router 1 --- Router 2 ---- Router 3--- Tunnel Tailend

-- Router 4 ---- Router 5----

MPLS-TE FRR protects a particular link or a particular node.

For link protection, the concept is to have a primary tunnel protected by a backup tunnel. The backup tunnel path should be on completely different and fault tolerant physical path when the primary tunnel path fails i.e. both the tunnels should not be in same SRLG links. In the above case if link between Router1-Router2-Router3 fails the tunnel should fallback over Router 4 and Router 5.

Detecting the link or node goes down should require a keepalive mechanism, usually RSVP hellos are used to detect the failure.

Node protection by default provides link protection. So when Router 2 goes down the traffic falls back over backup path.

MPLS-TE FRR wokrs by pre-signalling LSP over both primary and secondary paths even before the failure occurs. In normal conditions (with multiple path-option), only when primary LSP on primary path goes down, LSP gets signalled over secondary path option.

HTH

Arun