Tuesday, January 21, 2014

Segment Routing Traffic Engineering

In my previous post of Segment Routing: Alternate of LDP and RSVP, already discussed about the advantages of using SR w.r.t LDP. The utmost advantage of using Segment Routing is to steer the traffic which is normally called “Traffic Engineering”.

In case of MPLS we called Traffic Engineering as MPLS-TE but in case of Segment Routing, it could be SR-TE (Segment Routing Traffic Engineering Tunnel. RSVP is required to build the MPLS-TE tunnels along with LDP but in Segment Routing, all you need is the Segment IDs only. It is free from heavy RSVP signaling.

There are different ways to create Segment Routing Traffic Engineering Tunnels:-
1. Manually Create SR-TE tunnel and explicitly define the path. This is equivalent to MPLS-TE tunnel and define explicitly path by giving the next hop addresses.

2. Manually Create SR-TE tunnel but for path computation use PCE (Path Control Element). In this case headend router will become the PCC (Path Computation Client) and some software which sits outside of the network but has full view of topology will become a PCC. PCEP (Path Computation Element Protocol) is used between PCC and PCE. For reference http://tools.ietf.org/html/draft-sivabalan-pce-segment-routing-00

3. Dynamically Create SR-TE tunnel and compute path by using PCE. PCE is having API where user can push the headend and tailend routers information with some kind of SLAs. PCE will dynamically create the tunnel push it to router (PCC). Once this is done, PCC will ask for dynamic path also. For reference http://www.enog.org/presentations/enog-6/201-SR_ENOG.pdf

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