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RE: Reasons to deploy MPLS-TE

  • From: Puddinhead Wilson <puddinghead_wilson007@yahoo.co.uk>
  • Date: Thu, 6 May 2004 19:56:07 +0100 (BST)
  • Cc: mpls-ops@mplsrc.com
  • Resent-Date: Thu, 6 May 2004 15:55:32 -0400
  • To: sthaug@nethelp.no

Hi,
 
I agree BGP forwards only 1 route, yet how would you say FRR is slower?
 
take this case of how it wokrs in LDP/OSPF
1. we wait for an LSP to down to be detected
2. we then use new LSP after detection and using the protocol's database to see alternate route to node after receiving the "tigger".
 
Incase of BGP it would be:
1. VPNv4 route withdrawn, and hence the BGP update propgates a new route immediately after running decision making alogirhtm (implicit withdraw et al )
2. this amounts to *almost* the same propogation delay as case 1 above...does it not?
 
> If *FRR* is the biggest driver of TE, then that can be achieved by
> using BGP as an LDP also :) (or using any other LDP) as they would
> give us multiple LSPs to the same VPNv4 prefix :)?? Will they not?

The point of FRR, as I understand it, is mainly to let you reroute to
a predefined path in the seconds before your normal IGP converges to
a new path. I don't see how BGP can help you there - remember a BGP
speaker will only announce *one* best path to other BGP speakers.

Steinar Haug, Nethelp consulting, sthaug@nethelp.no

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