Re: [tcpm] RFC 1323: Timestamps option

On Fri, 26 Jan 2007, David Borman wrote:

> One of the topics that has been discussed in the past for the
> revision of RFC 1323 is to relax the requirement on when to send the
> Timestamps option.  I'd like to come to some resolution on this issue.
>
> Current:
> The Timestamps option is negotiated during the initial SYN exchange.
> If both sides support it, then every packet in the connection has to
> have the Timestamps option.

... snip ...

>
> My viewpoint
> ------------
> Right now, I'm inclined to leave the Timestamps option alone; you
> negotiate it during the SYN exchange, and then include it on every
> packet.  I'm willing to be convinced otherwise, but now I've placed a
> stake in the ground, and the mailing list will have to decide if
> there is sufficient reason to change the behavior.

The real problem is a zero configuration issue:  for the 100 million or so US
home users on DSL (or worse, compressing modems), timestamps offer little
gain and often substantial penalty.  For the 10 Million(?) US university
users, timestamps are necessary for good performance.  Who do you think the
manufacturers cater to? The simple answer is the home user, but many current
systems use some sort of heuristic (e.g. is the interface faster than 100
Mb/s?).

The current situation forces us to try to educate 9.99 million non-network
savvy users how to inspect and tweak their kernels.

I want ZERO config from at least 9.6 kbs to 9 Gbps.  Some form of late
timestamp negotiation is required before this can become the default.

(BTW Japan and Europe, with true high speed to the home might change the
equation quite a bit.  This path leads to some ugly market positions.)

Thanks,
--MM--

P.S.  The default WSCALE for MS Vista and mainline Linux is now 8 and 7
respectively for large memory systems, so the harder part of the zero config
problem has already been solved.  These correspond to 16 and 8 MByte TCP
buffers. Roll out is going to take a while, but that will give people a chance
to notice how the traffic might affect the network.  QoS anyone?

Thanks,
--MM--
-------------------------------------------
Matt Mathis      http://www.psc.edu/~mathis
Work:412.268.3319    Home/Cell:412.654.7529
-------------------------------------------
Evil is defined by mortals who think they know
"The Truth" and use force to apply it to others.

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