Re: [v6ops] Flow Label Load Balancing

Fernando Gont <fernando@gont.com.ar> Sat, 28 November 2020 03:50 UTC

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To: Tom Herbert <tom@herbertland.com>
Cc: Alexander Azimov <a.e.azimov@gmail.com>, tcpm <tcpm@ietf.org>, IPv6 Operations <v6ops@ietf.org>
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From: Fernando Gont <fernando@gont.com.ar>
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Subject: Re: [v6ops] Flow Label Load Balancing
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On 27/11/20 20:31, Tom Herbert wrote:
[....]
> 
> All we know in this case is that *TCP* has detected a connection is
> failing and there may be a potential problem with a path, we don't
> know that the network has detected any problems like some link is
> failing or will ever detect any problem. So in such a scenario, what
> recourse does the host have to try to salvage its connections?

None.

TCP times out and restransmits. And *the network* routes around failing 
paths.



> If the
> answer is that the host should always patiently wait for the network
> to figure out what is happening, then that's going to be a hard sell
> to application and host stack developers (remember the network is a
> black box from their perspective that they really don't trust).

Either that, of you switch to a different destination address if the 
transport protocol allows.



> If the
> answer is that the host is supposed to inform the network of issues
> with it's connections and then host and network work together to solve
> then that's great; 

The only thing the host can do is to switch to a different transport 
protocol if it allows.


> but then what is the general protocol that has been
> established to facilitate that and solved the problem of how hosts and
> network work together in concert to solve user's problems?

They don't really work together (modulo congestion control, one might 
argue), but rther complement each other (TCP times out and retransmits, 
and the network routes around failing paths).

Thanks,
-- 
Fernando Gont
e-mail: fernando@gont.com.ar || fgont@si6networks.com
PGP Fingerprint: 7809 84F5 322E 45C7 F1C9 3945 96EE A9EF D076 FFF1