Re: [tcpm] Fwd: New Version Notification for draft-yang-tcpm-ets-00.txt

[Bob Briscoe <[e-mail]>]

Hi, Kevin, Yuchung,

Here's the draft I referred to in the chat during your talk (and Richard 
mentioned it verbally): 
https://tools.ietf.org/html/draft-scheffenegger-tcpm-timestamp-negotiation-05

Here's the rationale behind the point both Richard and I tried to make 
in the tcpm WG just now:

You could define your new option solely with the last two negotiation 
fields.

Because the existing timestamp fields are already defined as opaque. So 
you can have a separate option just for the negotiation of what the 
existing timestamp option means (ie. its resolution).

Then, you don't force TCP to use a large option on the SYN, where space 
is critical. (But it  can use both options if there is space.)
This also gives you a fall-back if the other peer doesn't support the 
new option, but does support the old timestamp option.

The downside, is 2 extra bytes if TCP does use both options on the SYN. 
There might be other ways to arrange this, but the important thing is 
the requirements:
* fall-back during incremental deployment
* provide alternative ways to minimize space on SYN, so implementers can 
juggle priority of fitting in other options.

Cheers


Bob

On 03/11/2020 00:25, Yuchung Cheng wrote:
> Hi tcpm & iccrg,
>
> We are proposing a new TCP timestamp option to measure the network 
> delay more precisely (e.g. excluding delayed ACK effects) for 
> congestion control, e.g. Swift published SIGCOMM 2020. The precision 
> of the measurements can potentially be further enhanced by NIC 
> hardware timestamps. We are working on a reference implementation for 
> Linux as well.
>
> We'll also present it in the upcoming tcpm meeting. Feedbacks are very 
> welcome.
>
> ---------- Forwarded message ---------
> From: <[e-mail] <mailto:[e-mail]>>
> Date: Mon, Nov 2, 2020 at 3:29 PM
> Subject: New Version Notification for draft-yang-tcpm-ets-00.txt
> To: Eric Dumazet <[e-mail] <mailto:[e-mail]>>, 
> Yuchung Cheng <[e-mail] <mailto:[e-mail]>>, Neal 
> Cardwell <[e-mail] <mailto:[e-mail]>>, Kevin 
> Yang (Yudong) <[e-mail] <mailto:[e-mail]>>
>
>
>
> A new version of I-D, draft-yang-tcpm-ets-00.txt
> has been successfully submitted by Kevin (Yudong) Yang and posted to the
> IETF repository.
>
> Name:           draft-yang-tcpm-ets
> Revision:       00
> Title:          TCP ETS: Extensible Timestamp Options
> Document date:  2020-11-02
> Group:          Individual Submission
> Pages:          13
> URL: https://www.ietf.org/archive/id/draft-yang-tcpm-ets-00.txt
> Status: https://datatracker.ietf.org/doc/draft-yang-tcpm-ets/
> Htmlized: https://datatracker.ietf.org/doc/html/draft-yang-tcpm-ets
> Htmlized: https://tools.ietf.org/html/draft-yang-tcpm-ets-00
>
>
> Abstract:
>    This document presents ETS: an Extensible TimeStamps option for TCP.
>    It allows hosts to use microseconds as the unit for timestamps to
>    improve the precision of timestamps, and advertise the maximum ACK
>    delay for its own delayed ACK mechanism.  Furthermore, it extends the
>    information provided in the [RFC7323] TCP Timestamps Option by
>    including the receiver delay in the TSecr echoing, so that the
>    receiver of the ACK is able to more accurately estimate the portion
>    of the RTT that resulted from time traveling through the network.
>    The ETS option format is extensible, so that future extensions can
>    add further information without the overhead of extra TCP option kind
>    and length fields.
>
>
>
>
> Please note that it may take a couple of minutes from the time of 
> submission
> until the htmlized version and diff are available at tools.ietf.org 
> <http://tools.ietf.org>.
>
> The IETF Secretariat
>
>
>
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Bob Briscoe                               http://bobbriscoe.net/
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