Subject: Re: [tcpm] Fwd: New Version Notification for draft-touch-tcpm-experimental-options-00.txt

From: Wesley Eddy <[email-masked]>
Date: Wed, 09 Nov 2011 09:51:09 -0500

On 10/24/2011 5:57 PM, Joe Touch wrote:
> Hi, all,
>
> The following document describes an informal proposal I made on the list
> a while back. Hopefully we can discuss it in Taiwan.
>

After reading and thinking about it, I think we should adopt this.

I think this should be more than just Informational, if people agree
that it's the best way to disambiguate between concurrent experiments,
then I would think that it should be a Best Current Practice.

Some specific comments:

- I believe there are other devices (e.g. Bluecoat) that are also
   using the experimental codepoints (not just the AO precursor and
   the TCP-CT code).

- We might add some analysis that says:

   Hosts (or routers) that have deployed the pre-TCP-AO option using
   the experimental codepoints will generally be limited to BGP-speakers
   or other infrastructure, and not consumer devices or servers at the
   edges of the network that would be participating in other TCP
   experiments.  There is not expected to be an issue with use of this
   nonce for new experimental options to conflict with these.

   Middleboxes deployed using the experimental codepoints for discovering
   each other are expected to pass-through experimental options using the
   nonce discussed in this document, based on discussion with the vendor.
   These middleboxes have their own mechanism for disambiguating their
   use of the codepoints from other uses.

- I think we would encourage new experimental options to strongly make
   use of this nonce mechanism, but say something about the fact that
   if they don't, their odds of causing trouble for other experimental
   options that do use a nonce are small, however the odds of code that
   uses non-nonced   options getting confused while attempting to
   parse nonced options may be greater!  Thus, it's strongly encouraged
   to use a nonced format, and in one's best interest.

- Consider borrowing (or adapting) some of the text from section 1 of
   draft-eddy-tcpm-addl-exp-options-00, in order to motivate why we need
   to encourage this rather than continue to allow the option space to
   be reduced by squatting.

Thanks for writing this!

-- 
Wes Eddy
MTI Systems

---

From: Jerry Chu <[email-masked]>
Date: Sun, 13 Nov 2011 23:37:38 -0800

Hi Joe,

On Mon, Oct 24, 2011 at 2:57 PM, Joe Touch <[email-masked]> wrote:

> Hi, all,
>
> The following document describes an informal proposal I made on the list a
> while back. Hopefully we can discuss it in Taiwan.
>

This sounds like a good idea, to remove IANA involvement hence encouraging
more
rapid experiments, at a small cost of using more bytes in the precious
option space.

I have only a couple of comments:

1. "The nonce is selected by the protocol designer when the experimental
   option is defined. The Nonce is selected any of a variety of ways,
   e.g., using the Unix time() command or bits selected by an arbitrary
   function (such as a hash)."

Although the first sentence above was clear in saying the nonce was picked
statically at the design time, the second sentence almost sounded like one
picked dynamically.

Also I wonder besides pure randomness, is there other idea the can be used
to further minimize the chance of collision, e.g., including the length
field as
a differentiator or embedding some notion of calendar time in the nonce...

2. "The length of the nonce is intended to be 32 bit in network standard
   byte order. It can be shorter if desired (e.g., 16 bits), with a
   corresponding increased probability of collision and thus false
   positives."

Is one byte nonce allowed, considering how tight the option space has
become thus every byte of saving counts, or it's not worth the saving
because most stack implementations choose to alight each option...?

Also is the choice of the nonce size all up to the protocol designers?
If so, perhaps some guideline can be provided on how to minimize the
chance of collision. E.g., an experimental option with a data field
containing
possibly wide range of value may suffice with just one byte nonce because
the chance of collision is low (?). Also should the length field be
considered
as a differentiator when choosing the size of the nonce?

Jerry

> Joe
>
> -------- Original Message --------
> Subject: New Version Notification for draft-touch-tcpm-experimental-**
> options-00.txt
> Date: Mon, 24 Oct 2011 14:53:10 -0700
> From: [email-masked]
> To: [email-masked]
> CC: [email-masked]
>
> A new version of I-D, draft-touch-tcpm-experimental-**options-00.txt has
> been successfully submitted by Joe Touch and posted to the IETF repository.
>
> Filename:        draft-touch-tcpm-experimental-**options
> Revision:        00
> Title:           Shared Use of Experimental TCP Options
> Creation date:   2011-10-24
> WG ID:           Individual Submission
> Number of pages: 6
>
> Abstract:
>   This document describes how TCP option codepoints can support
>   concurrent experiments. The suggested mechanism avoids the need for
>   a coordinated registry, and is backward-compatible with currently
>   known uses.
>
>
>
>
>
> The IETF Secretariat
> ______________________________**_________________
> tcpm mailing list
> [email-masked]
> https://www.ietf.org/mailman/**listinfo/tcpm<https://www.ietf.org/mailman/listinfo/tcpm>
>

---

From: Yuchung Cheng <[email-masked]>
Date: Tue, 15 Nov 2011 13:06:33 -0800

I also support this draft and have similar comments to Jerry's plus:

If we expect running implementations, shouldn't the target status be standard?