Re: [tcpm] I-D Action:draft-ietf-tcpm-tcp-auth-opt-01.txt

touch@ISI.EDU Fri, 18 July 2008 15:59 UTC

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Date: Fri, 18 Jul 2008 08:59:51 -0700
From: touch@ISI.EDU
To: Stefanos Harhalakis <v13@v13.gr>
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Cc: Adam Langley <agl@imperialviolet.org>, tcpm@ietf.org
Subject: Re: [tcpm] I-D Action:draft-ietf-tcpm-tcp-auth-opt-01.txt
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Quoting Stefanos Harhalakis <v13@v13.gr>:

..
> There are not many more things to report that those discussed in the list:
> * The ability to store more options when necessary
> * 4 bytes of extra space for data when TSs and SACKs are included
> * 4xN less bytes transmitted over the network in each session (where N is the
> 
> number of segments with TS+SACK that are sent)
> 
> From a very sallow test/accounting I've just performed (1 minute run) on a 
> linux firewall for a not so large, not congested network, it seems that about
> 
> 3-4% of the TS segments also include a SACK header and that there could be 
> saved about 1 byte every 7-8 TS-enabled segments (not counting SYN
> segments).
..
> that where transmitted as NOOP and could be saved (only counts 32 bit 
> words)).
> 
> Is it worth?

If nothing changes, probably not. However, legacy TCP is likely to be around for
a while, so conservation is critical to using that space for other things.

Also, the space is most critical in the SYNs; that is the only place where
capabilities are negotiated.

Joe

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