On Wed, 9 Jun 2021 at 01:18, Adam Thompson <athompson@merlin.mb.ca> wrote:

If your work results in actionable recommendations such as "don't use BGP out-delay timers to mitigate XYZ in circumstance LMNO, do ABC instead", that's fantastic.  Please keep us advised, and do post aggregated survey results here once you close the survey.

What is actionable? What is the goal? The question as OP presented contains some assumptions

a) better convergence is needed
b) MRAI is important part of the solution space

Neither are provable. We already know how to make DFZ convergence really fast (or at least orders of magnitude faster than it is), that information exists, but that isn't deployed because customers are not asking for it, so providers are not aware that there is room for improvements.

Things don't optimise to be as good as they can be, things optimise to be as bad as the market allows them to be. And the market accepts the DFZ convergence.

If you do decide to optimise for DFZ convergence, without commercial pressure, you will risk lower availability, because you'll be using configuration less tested by other customers and everyone knows how terrible quality every NOS is. Everyone finds novel bugs, in the same damn protocols we've ran +20 years. It's like running Windows and Linux and regularly finding out listing files in a directory breaks your service, year after year after year.

For those who are interested in better convergence
   - change your interface down reporting to 0 (there may be delay before interface down is reported to system, so that optical protection works without causing outage)
   - use 'add-path' or at least 'best-external' in iBGP, so that you always have backup eBGP route immediately available once best is invalidated (normally you have lot of delay to find next best, once you lose your best eBGP)
   - tie your route validity to IGP, so you can invalidate your BGP the moment IGP disappears
   - ensure IGP converges fast (another topic)
   - set MRAI to 0
   - use PIC edge
   - ensure your BGP NLRI can be as large as MTU allows
   - ensure your convergence isn't bottle necked by slow peer in group
   - ensure you are not dropping received TCP packets on punt path
   - ensure your fast external fallover works (eBGP down, on int down) this is quite easy to break
   - then ensure everyone else in the DFZ does the same thing



But from a business POV, don't do any of this, you will have more bugs and lower availability and your customers will be less happy.



I am specifically interested in the answer to "Have you ever had to adjust BGP out-delay with any of your peers, and why?"  It would be great if we could derive that answer from the survey results, but anecdotal replies here would also be helpful.  All you larger(-than-me) network operators out there: when would I need to use out-delay?  Why?  What does it accomplish?

Good luck in reformulating your survey to get better engagement,
-Adam

Adam Thompson
Consultant, Infrastructure Services
1593169877849
100 - 135 Innovation Drive
Winnipeg, MB, R3T 6A8
(204) 977-6824 or 1-800-430-6404 (MB only)
athompson@merlin.mb.ca
www.merlin.mb.ca


From: NANOG <nanog-bounces+athompson=merlin.mb.ca@nanog.org> on behalf of Saku Ytti <saku@ytti.fi>
Sent: June 8, 2021 01:06
To: shahrooz@cs.umass.edu <shahrooz@cs.umass.edu>
Cc: nanog list <nanog@nanog.org>; Arun Venkataramani <arun@cs.umass.edu>
Subject: Re: A survey on BGP MRAI timer values in practice
 
On Mon, 7 Jun 2021 at 19:32, <shahrooz@cs.umass.edu> wrote:

> We often read that the Internet (i.e. BGP) has a long convergence delay.
> But why is it so slow? And can we (researchers) do anything about it?

Create business incentives to improve it. This is a non-technical
problem, we've long had technical tools to make it fast, there just
isn't incentive to make it fast. Customers are not asking operators
for better convergence speeds.

> Please help us out to find out by answering our short anonymous survey
> (<10 minutes).

Can you tell me what have you done so far? What are the default MRAI
values for each AFI/SAFI for IOS, IOS-XR, Junos, SROS, VRP and EOS?
Then people responding don't have to check what their NOS does, they
can refer to your table and tell the default value, since this is what
>99% will be using.

Now your survey has built-in selection bias, people who answer it are
people who know what it is and who are concerned about it and have
changed it, this is not a representative group and you will start your
work with very bad data.



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  ++ytti


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  ++ytti