Re: [v6ops] Flow Label Load Balancing

Fernando Gont <fernando@gont.com.ar> Sat, 28 November 2020 08:42 UTC

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To: Mark Smith <markzzzsmith@gmail.com>
Cc: Tom Herbert <tom@herbertland.com>, IPv6 Operations <v6ops@ietf.org>, tcpm <tcpm@ietf.org>
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From: Fernando Gont <fernando@gont.com.ar>
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Date: Sat, 28 Nov 2020 05:01:50 -0300
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Subject: Re: [v6ops] Flow Label Load Balancing
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On 28/11/20 03:42, Mark Smith wrote:
> 
> 
> On Sat, 28 Nov 2020, 14:52 Fernando Gont, <fernando@gont.com.ar 
> <mailto:fernando@gont.com.ar>> wrote:
> 
>     On 27/11/20 21:32, Mark Smith wrote:
>      >
>      > On Sat, 28 Nov 2020, 10:32 Tom Herbert, <tom@herbertland.com
>     <mailto:tom@herbertland.com>
>      > <mailto:tom@herbertland.com <mailto:tom@herbertland.com>>> wrote:
>     [....]
>      >
>      > If hosts start trying to take control of steering traffic by
>     varying the
>      > flow label value within a flow, making the network's job harder,
>     and the
>      > network being blamed for the possibility bad network performance
>     that
>      > may result, the response will be both quick and easy - network
>     operators
>      > will switch off looking the Flow Label.
> 
>     THat is *exactly* why I noted that I'm concerned that we seem to be on
>     the path of making the FLow Label unusable.
> 
> 
> I see the Flow Label as a hint, but only a hint, of what the hosts wants 
> from the network. It's useful as an expression of what the host would 
> like to have.

As you correctly noted, it's supposed to be an identifier of the flow, 
because it's hard to get for the port numbers.

I don't think it can bee seen as ad expression of what the host wants to 
ahve, because the Flow ID has no semantics, and the host doesn't even 
know what's in the network.



> However, if that hint causes me any trouble, I'll ignore it and then 
> devolve to trying to deliver the packet based just on its destination 
> address.

If you *needed* (or could make use of) the FL, then, if it causes 
trouble, you either resort to finding the five-tuple, or quite likely 
end of dropping packets.

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