bfd-like mechanism for LANPHY connections between providers

Sudeep Khuraijam skhuraijam at liveops.com
Wed Mar 16 19:00:20 CDT 2011


Correct me if I am wrong but to detect a failure by default BGP would wait the "hold-timer" then declare a peer dead and converge.
Hence the case for BFD.

There a difference of several orders of magnitude  between BFD keepalive intervals  (in ms) and BGP (in seconds) with generally configurable multipliers vs. hold timer.
With Real time media and ever faster last miles, BGP hold timer may find itself inadequate, if not in appropriate in some cases.

For a provider to require a vendor instead of RFC compliance is sinful.

Sudeep
On Mar 16, 2011, at 1:42 PM, Jensen Tyler wrote:

Correct me if I am wrong but to detect a failure by default BGP would wait the "hold-timer" then declare a peer dead and converge.

So you would be looking at 90 seconds(juniper default?) + CPU bound convergence time to recover? Am I thinking about this right?

-----Original Message-----
From: Jeff Wheeler [mailto:jsw at inconcepts.biz]
Sent: Wednesday, March 16, 2011 1:55 PM
To: nanog at nanog.org<mailto:nanog at nanog.org>
Subject: Re: bfd-like mechanism for LANPHY connections between providers

On Wed, Mar 16, 2011 at 2:33 PM, Jensen Tyler <JTyler at fiberutilities.com<mailto:JTyler at fiberutilities.com>> wrote:
We have many switches between us and Level3 so we don't get a "interface down" to drop the session in the event of a failure.

This is often my topology as well.  I am satisfied with BGP's
mechanism and default timers, and have been for many years.  The
reason for this is quite simple: failures are relatively rare, my
convergence time to a good state is largely bounded by CPU, and I do
not consider a slightly improved convergence time to be worth an
a-typical configuration.  Case in point, Richard says that none of his
customers have requested such configuration to date; and you indicate
that Level3 will provision BFD only if you use a certain vendor and
this is handled outside of their normal provisioning process.

For an IXP LAN interface and associated BGP neighbors, I see much more
advantage.  I imagine this will become common practice for IXP peering
sessions long before it is typical to use BFD on
customer/transit-provider BGP sessions.

--
Jeff S Wheeler <jsw at inconcepts.biz<mailto:jsw at inconcepts.biz>>
Sr Network Operator  /  Innovative Network Concepts



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Sudeep Khuraijam | I speak for no one but I










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