Re: [Lsr] Why only a congestion-avoidance algorithm on the sender isn't enough

Christian Hopps <chopps@chopps.org> Sun, 03 May 2020 23:27 UTC

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From: Christian Hopps <chopps@chopps.org>
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Date: Sun, 3 May 2020 19:27:20 -0400
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Subject: Re: [Lsr] Why only a congestion-avoidance algorithm on the sender isn't enough
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> On Apr 30, 2020, at 9:57 AM, Henk Smit <henk.ietf@xs4all.nl> wrote:
> 
> I still think we'll end up re-implementing a new (and weaker) TCP.

Hi Henk,

Thanks for the thoughtful writeup. Let's not be too cynical at the start though! :)

I'd note that our environment is a bit more controlled than the end-to-end internet environment. In IS-IS we are dealing with single link (logical) so very simple solutions (CTS/RTS, ethernet PAUSE) could be viable. That aside, yes, there are queues and opportunity for loss between the receiving linecard interface and the IS-IS process on the router, but that path is much more accessible (controllable) to the control loop than all the routers and networks between 2 endpoints for an internet TCP connection.

Also, while it's generally accepted that end-to-end internet based protocols need to be TCP friendly (e.g., the datagram-based congestion control algorithms (DCCP)), I'm not sure this requirement needs to be applied the same way for IS-IS. Thus our choice of algorithms may well be less restricted.

Thanks,
Chris.
[as WG member]