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Re: Global Crossing Contact / BGP and SONET interaction question

  • From: Ian Mason
  • Date: Wed Jul 26 09:04:54 2006

On 26 Jul 2006, at 08:29, Forrest W Christian wrote:

Randy Epstein wrote:
I don't have an answer to the root cause of your problem, and I'm not looking for a discussion on route dampening (there are enough debates onthis issue to make your head spin), but may I suggest you raise your hold timers to prevent your BGP sessions from going down on short disturbances as these?
From what I can tell the disturbances are less than a second in duration. It doesn't appear that this is a hold-timer issue, although I would like GX to set it at something higher than 90 seconds (mine is already at a higher value- but the lower value wins during negotiation). I really suspect that either a) GX has some semi-weird configuration where the SONET ring switching from the normal to the protect path and back causes BGP to reset on the border router I'm attached to or b) There is a separate issue which is causing BGP to flap. Or of course, something else completely different.

Unfortunately, I haven't been able to figure out how to talk to anyone at GX which actually has access to the routers and knows anything about BGP.

The timing of protection switching on a SONET ring is of completely the wrong order to upset a BGP session. From memory there's a designed in upper bound of 200 mS from fault to fully restored with typical values being more like 50 mS.

One possibility that occurs to me is that the A end here might be using a router with a SONET card, and the router software is propagating a SONET event through the stack causing BGP to react to an event it wouldn't even see on a physically separate SONET ADM. That is pure speculation though.