Re: bfd-like mechanism for LANPHY connections between providers

[Sudeep Khuraijam <skhuraijam () liveops com>]

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 () inconcepts biz]
Sent: Wednesday, March 16, 2011 1:55 PM
To: nanog () nanog org<mailto:nanog () nanog org>
Subject: Re: bfd-like mechanism for LANPHY connections between providers

On Wed, Mar 16, 2011 at 2:33 PM, Jensen Tyler <JTyler () fiberutilities com<mailto:JTyler () 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 () inconcepts biz<mailto:jsw () inconcepts biz>>
Sr Network Operator  /  Innovative Network Concepts



____________________________________________
Sudeep Khuraijam | I speak for no one but I