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Re: [babel] Congestion control [was: Open issues...]

Dave Taht <dave.taht@gmail.com> Fri, 26 July 2019 23:30 UTC

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From: Dave Taht <dave.taht@gmail.com>
Date: Fri, 26 Jul 2019 16:30:19 -0700
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To: Juliusz Chroboczek <jch@irif.fr>
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Subject: Re: [babel] Congestion control [was: Open issues...]
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On Fri, Jul 26, 2019 at 2:41 PM Juliusz Chroboczek <jch@irif.fr> wrote:
>
> > B) As you have larger numbers of routes (1000s), congestion control
> > becomes a problem
>
> I'm pretty sure that packet pacing (spreading the announcements over the
> update interval rather then sending them all as a burst as we currently do)
> would solve your issues, Dave.

I think it would make a big difference yes. Ain't a lot of code,
either, and the upcoming
release of openwrt is mostly 4.14 based. I can go toss the patch together again.

> This won't happen for 1.9, which I'd like to release before the summer ends.

Would love to see that make this openwrt release.

>
> > My "solution" for some congestion control issues is to start dynamically
> > increasing the route announcement interval for stabler routes, while
> > still announcing the most important ones (like defaults) in the
> > hello. the protocol has an underused feature where we can announce a per
> > route interval larger than the default.
>
> Indeed.  This can be done in addition to packet pacing.

I think this is a good long term solution to larger numbers of routes
on stabler networks.

In either case the "fitting" algorithm for these two approaches either
separate or combined has to somehow stay below the allocated
bandwidth, and we need more experience with unicast and real networks
than we have as yet.

It's not enough though, to get to my (personal) goal of being able to
carry a full ipv6 route table (64k routes); too many scalability
issues
in the code itself.

>
> -- Juliusz

I also keep hoping somehow someday we'll get to atomic updates. The
nexthop code finally landed in 5.2? (3?) netlink, so that can safely
wait til after 1,9.


-- 

Dave Täht
CTO, TekLibre, LLC
http://www.teklibre.com
Tel: 1-831-205-9740

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