Re: [ippm] [tsvwg] New Internet Draft: Congestion Signaling (CSIG)

[Tom Herbert <[e-mail]>]

On Fri, Feb 9, 2024 at 10:53 PM Nandita Dukkipati <[e-mail]> wrote:
>
> Hi Tom,
>
> We updated the draft, correcting some nit errata, and to not let the draft expire. It's not discussed in any other mailing lists.

Thanks Nandita.

I still have fundamental concerns about the protocol layering in this
draft, please see my previous comments on that. The draft defines a
protocol for end-to-end network to host signaling and IMO, such a
protocol belongs in the network layer but the draft puts the protocol
in L2 and L4 and seems to avoid L3 without explanation. IOAM defines a
very similar method of signaling and RFC9486 is a good model for
network layer protocol that provides network to host signaling.

Tom

>
> Nandita
>
> On Thu, Feb 8, 2024 at 3:53 PM Tom Herbert <[e-mail]> wrote:
>>
>> Hi,
>>
>> I noticed there is now an -01 version of the draft posted on Feb. 2.
>> Is this draft being discussed on some other list?
>>
>> Thanks,
>> Tom
>>
>> On Sat, Sep 9, 2023 at 9:09 AM Tom Herbert <[e-mail]> wrote:
>> >
>> > Hi, thanks for draft!
>> >
>> > The first thing that stands out to me is the carrier of the new packet headers. In the forward path it would be in L2 and in reflection it would be L4. As the draft describes, this would entail having to support the protocol in multiple L2 and multiple L4 protocols-- that's going to be a pretty big lift! Also, L2 is not really an end-to-end protocol (would legacy switches in the path also forward the header)l?).
>> >
>> > The signaling being described in the draft is network layer information, and hence IMO should be conveyed in network layer headers. That's is L3 which conveniently is the average of L2+L4 :-)
>> >
>> > IMO, the proper carrier of the signal data is Hop-by-Hop Options. This is end-to-end and allows modification of data in-flight. The typical concern with Hop-by-Hop Options is high drop rates on the Internet, however in this case the protocol is explicitly confined to a limited domain so I don't see that as a blocking issue for this use case.
>> >
>> > The information being carried seems very similar to that of IOAM (IOAM uses Hop-by-Hop Options and supports reflection). I suppose the differences are that this protocol is meant to be consumed by the transport Layer and the data is a condensed summary of path characteristics. IOAM seems pretty extensible, so maybe it could be adapted to carry the signals of this draft?
>> >
>> > A related proposal might be FAST draft-herbert-fast. Where the CSIG is network to host signaling, FAST is host to network signaling for the purposes of requesting network services. These might be complementary and options for both may be in the same packet. FAST also uses reflection, so we might be able to leverage some common implementation at a destination.
>> >
>> > Tom
>> >
>> > On Fri, Sep 8, 2023, 7:43 PM Abhiram Ravi <abhiramr=[e-mail]> wrote:
>> >>
>> >> Hi IPPM folks,
>> >>
>> >> I am pleased to announce the publication of a new internet draft, Congestion Signaling (CSIG): https://datatracker.ietf.org/doc/draft-ravi-ippm-csig/
>> >>
>> >> CSIG is a new end-to-end packet header mechanism for in-band signaling that is simple, efficient, deployable, and grounded in concrete use cases of congestion control, traffic management, and network debuggability. We believe that CSIG is an important new protocol that builds on top of existing in-band network telemetry protocols.
>> >>
>> >> We encourage you to read the CSIG draft and provide your feedback and comments. We have also cc'd the TSVWG, CCWG, and ICCRG mailing lists, as we believe that this work may be of interest to their members as well.
>> >>
>> >> Thank you for your time and consideration.
>> >>
>> >> Sincerely,
>> >> Abhiram Ravi
>> >> On behalf of the CSIG authors