[138808] in North American Network Operators' Group
Re: bfd-like mechanism for LANPHY connections between providers
daemon@ATHENA.MIT.EDU (Sudeep Khuraijam)
Wed Mar 16 20:01:15 2011
From: Sudeep Khuraijam <skhuraijam@liveops.com>
To: Jensen Tyler <JTyler@fiberutilities.com>
Date: Wed, 16 Mar 2011 17:00:20 -0700
In-Reply-To: <1A8A762BD508624A8BDAB9F5E1638F945FB4C3C43A@comsrv01.fg.local>
Cc: "nanog@nanog.org" <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
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 in=
tervals (in ms) and BGP (in seconds) with generally configurable multiplie=
rs vs. hold timer.
With Real time media and ever faster last miles, BGP hold timer may find it=
self 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 converg=
ence 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<ma=
ilto:JTyler@fiberutilities.com>> wrote:
We have many switches between us and Level3 so we don't get a "interface do=
wn" 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
