Re: [tcpm] Catalog approach for syn option aggregation draft

Hi Michael,

Yes, the pcap files I've used don't have much v6 traffic, so I only
collected 1.4M syn packets for IPv6. But, the most dominant value for MSS
is 1440 (more than 60%)
So, I think your suggestion makes sense to me.
Thank you so much!
--
Yoshi

On Fri, Jul 7, 2023 at 12:41 AM Scharf, Michael <
Michael.Scharf@hs-esslingen.de> wrote:

> Hi Yoshi,
>
>
>
> Regarding the MSS: Isn’t the MSS for IPv6 only 1440 byte?
>
>
>
> Just as a thought: Instead of encoding an MSS value, 1 bit could be used
> to convey “if set to 1, use the maximum MSS for the Ethernet MTU of 1500
> byte”?
>
>
>
> Disclaimer: I haven’t thought about the implications on IPv4/IPv6
> translation techniques. But, anyway, the bigger problem may be the
> installed base of MSS clamping…
>
>
>
> Michael
>
>
>
> *From:* tcpm <tcpm-bounces@ietf.org> *On Behalf Of * Yoshifumi Nishida
> *Sent:* Friday, July 7, 2023 8:40 AM
> *To:* tcpm@ietf.org Extensions <tcpm@ietf.org>
> *Subject:* [tcpm] Catalog approach for syn option aggregation draft
>
>
>
> Hi folks,
>
>
>
> During my presentation for syn aggregation draft in the last WG meeting,
> some folks suggested using a catalog approach to compress existing options
> such as MSS, wscale, etc.
>
> I am still thinking, but I've put some initial ideas about this approach
> in the updated version of the draft.
>
>
>
> In a nutshell, the idea is to use entire bits for 'Group 1'. As one group
> can carry 6 bits, we use 4 bits for window scale option, 1 bit for
> SACK-permit and another 1 bit for MSS.
>
> As window scale value ranges from 0 to 14, we can accomodate all values in
> 4 bits.
>
> SACK-permit carries 1 bit information, so using 1 bit is enough.
>
> MSS is a bit tricky as it can carry various values. But, as far as I've
> checked 24M syn packets in CAIDA and WIDE's packet captures, over 40% MSS
> options in SYN packets carries 1460.
>
> Hence, the draft uses 1 bit to indicate MSS=1460.
>
>
>
> Since I'm still wondering if this format is fine or there might be more
> efficient ways, your feedback is highly appreciated.
>
> If you're interested, please check the updated draft.
>
> Thank you so much!
>
> --
>
> Yoshi
>
>
>
>
>
>
>
> ---------- Forwarded message ---------
> From: <internet-drafts@ietf.org>
> Date: Wed, Jul 5, 2023 at 1:24 AM
> Subject: I-D Action: draft-nishida-tcpm-agg-syn-ext-04.txt
> To: <i-d-announce@ietf.org>
>
>
>
>
> A New Internet-Draft is available from the on-line Internet-Drafts
> directories.
>
>    Title           : Aggregated Option for SYN Option Space Extension
>    Author          : Yoshifumi Nishida
>    Filename        : draft-nishida-tcpm-agg-syn-ext-04.txt
>    Pages           : 11
>    Date            : 2023-07-05
>
> Abstract:
>    TCP option space is scarce resource as its maximum length is limited
>    to 40 bytes.  This limitation becomes more significant in SYN
>    segments as all options used in a connection should be exchanged
>    during SYN negotiations.  This document proposes a new SYN option
>    negotiation scheme that can aggregate multiple TCP options in SYN
>    segments into a single option so that more options can be negotiate
>    during 3-way handshake.  With its simple design, the approach does
>    not require fundamental changes in TCP.
>
> The IETF datatracker status page for this Internet-Draft is:
> https://datatracker.ietf.org/doc/draft-nishida-tcpm-agg-syn-ext/
>
> There is also an HTML version available at:
> https://www.ietf.org/archive/id/draft-nishida-tcpm-agg-syn-ext-04.html
>
> A diff from the previous version is available at:
> https://author-tools.ietf.org/iddiff?url2=draft-nishida-tcpm-agg-syn-ext-04
>
> Internet-Drafts are also available by rsync at rsync.ietf.org:
> :internet-drafts
>
>
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