[AusNOG] BGP hold timer values

[Alex Samad - Yieldbroker]

Thanks.

Brings me back to BFD, how many providers use this. Is anyone using this with eBGP

A

From: Andrew Jones [mailto:Andrew.Jones at optus.com.au]
Sent: Wednesday, 28 January 2015 9:33 AM
To: Alex Samad - Yieldbroker; Tom Berryman
Cc: ausnog at lists.ausnog.net
Subject: RE: [AusNOG] BGP hold timer values

There is a lot more factors in play for BGP to converge than just hello/hold timers.

This is a good article to read:

http://blog.ine.com/2010/11/22/understanding-bgp-convergence/

Cheers,

Andrew Jones

From: AusNOG [mailto:ausnog-bounces at lists.ausnog.net] On Behalf Of Alex Samad - Yieldbroker
Sent: Tuesday, 27 January 2015 11:19 PM
To: Tom Berryman
Cc: ausnog at lists.ausnog.net<mailto:ausnog at lists.ausnog.net>
Subject: Re: [AusNOG] BGP hold timer values

Hi

I will have to monitor that.

We suffered from an outage recently, with a provider we have 2 links with.  We have multiple providers.
As a review of the incident the business asked about the 3m hold timer. In theory the way I read it, is the routes could be held for up to 3 min whilst the link is down...


One of the questions was why did it take soo long ~ 8-9min for traffic to appear on the other link.  Waiting for feedback on that
I am presuming with a lower hold timer/keep alive I can get pretty fast response as its only on this providers network I am failing over.

Alex


From: Tom Berryman [mailto:Tom at connectivityit.com.au]
Sent: Tuesday, 27 January 2015 11:09 PM
To: Alex Samad - Yieldbroker
Cc: David Hughes; ausnog at lists.ausnog.net<mailto:ausnog at lists.ausnog.net>
Subject: Re: [AusNOG] BGP hold timer values

There is a bit more than just a few extra packets (as your cost) - BGP can/does have notable CPU impact on low-mid range routing gear.

With eBGP, you are talking propagation of your routes to the internet, so not all of the internet is going to see your changes for maybe up to 180 seconds. That said, it's likely most of it will be sooner than that.

Tom



On 27 Jan 2015, at 11:01 pm, Alex Samad - Yieldbroker <Alex.Samad at yieldbroker.com<mailto:Alex.Samad at yieldbroker.com>> wrote:

Hi

Okay its eBGP, currently have 4 providers, some with multiple connections. So I am thinking 6 / 20 might be good for me, business requirement for approx. 30sec response.
I am presuming all I am looking at is extra BGP packets .. every 6 sec compared to 1 min..


Alex
-----Original Message-----
From: David Hughes [mailto:david at hughes.com.au]
Sent: Tuesday, 27 January 2015 9:37 PM
To: Alex Samad - Yieldbroker
Cc: ausnog at lists.ausnog.net<mailto:ausnog at lists.ausnog.net>
Subject: Re: [AusNOG] BGP hold timer values


I gave a lightning talk about this sort of thing a while ago at an APRICOT.  I just
googled to find the slides and can now see just how many years ago it was.
Gotta say I'm feeling old :)

But, it's probably still relevant although the defaults may have changed.  This
reflected what we were running at the time - and we were trying to be
pretty aggressive.

http://archive.apnic.net/meetings/21/docs/sigs/routing/routing-
pres-hughes-bgp.pdf

For reference I'm currently happy to run

eBGP
: 10 / 30
iBGP
: 5 / 15

And I'd run this even to a single upstream.  If it fails at least you'll have
something in your logs to say why you fell off the net for a while.  Silent
failures are a bugger to troubleshoot.


Thanks

David
...



On 27/01/2015, at 6:47 PM, Alex Samad - Yieldbroker
<Alex.Samad at yieldbroker.com<mailto:Alex.Samad at yieldbroker.com>> wrote:
Hi

I'm wonder what is considered "best practice" or good/responsible hold
timer values for BGP.

Currently I'm set at 3m, but I am considering lowering this to 30s and keep
alive down to 20s, potentially even lower. Or if possible to use BFD & BGP,
what's the uptake on BFD ?

Alex
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