netdev - Re: [PATCH net-next 6/6] sched: Eliminate use of flow_keys in sch

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Date:	Mon, 02 Mar 2015 12:02:27 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Tom Herbert <therbert@...gle.com>
Cc:	netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 6/6] sched: Eliminate use of flow_keys in
 sch_sfq

On Mon, 2015-03-02 at 11:51 -0800, Tom Herbert wrote:
> On Mon, Mar 2, 2015 at 11:43 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> > On Mon, 2015-03-02 at 11:34 -0800, Tom Herbert wrote:
> >
> >> Spraying would be quite easy by modulating txhash from TCP and using
> >> either  UDP encapsulation like GUE or IPv6 flow labels. Only problem
> >> is that this would constantly be changing rxhash at the receiver for
> >> the connection, although flow labels might 'just work' with IPv6
> >> Toeplitz in NICs.
> >
> > When I said 'regular IPv4/tcp traffic' this did not include any added
> > encapsulation.
> >
> > Most NIC are not able to properly offload TCP (TSO) with such
> > encapsulations.
> >
> IPv6 flow labels should work through TSO, they would just be
> replicated for each segment. You would need switches that can hash
> based on flow label though, and of course IPv6 deployed in the network
> :-).


Yeah, but I explicitly talked about native IPv4 + TCP ;)

not IPv6 + TCP, or IPv6 + IPV4 + TCP or some encapsulation...

Trend is to generalize random packet spraying, even within a flow.

https://www.cs.purdue.edu/homes/kompella/publications/infocom13.pdf

This forces us to build a resilient TCP stack.


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