Re: [tsvwg] Advance notice on request to poll TSVWG for adoption of draft-kaippallimalil-tsvwg-media-hdr-wireless-03

[Tom Herbert <[e-mail]>]

On Fri, Oct 27, 2023 at 4:35 PM Kaippallimalil John
<[e-mail]> wrote:
>
> Hi Tom, Joe,
>
>
>
> With regard to the concerns from Tom and Joe, the behavior needed is outlined in slide 3 of: https://datatracker.ietf.org/meeting/118/materials/slides-118-tsvwg-sessa-92-media-header-extensions-for-wireless-networks
>
>
>
> IPv6 HBP does not currently provide the capability needed:
>
> IPv6 HBH (MED in this case) is provisioned in the “Application Provider” (AP) domain. And the service provided in the same domain (AP domain in this case)
> But that is not what we want. MED is inserted by AP domain, and read in the wireless provider domain.

Hi John,

Can you clarify what "inserted" means in this context? (the word has
confusingly been used in different contexts). For instance, there are
three uses I know of:

1) A packet was created by a hosts with the data ("inserted" probably
isn't the best term for this)
2) A packet is encapsulated inflight and the data is attached to the
outer headers
3) The data is inserted into a packet while it's inflight with (no
encapsulation)

#1 and #2 are generally acceptable (technically, in both cases a host
is creating the packets so HBH options or UDP options can be set in
the packet safely). #3 is a bit more controversial, but there have
been proposals for this like inserting a segment routing header in
packets in flight.

Please also clarify the processing of the wireless node.

1) Is the wireless always the destination endpoint of UDP
encapsulation? If so then it would be appropriate for it to process
UDP options in the encapsulation since it's the destination of the
encapsulated packet
2) Does the wireless node is inspect the UDP options in flight as an
anonymous router in the path that forwards packets and isn't the
destination of the packet? In that case, I think using UDP Options is
problematic (or putting the information into the UDP payload like SPUD
proposed)

> The data in MED is sent per packet and

FAST allows data to be changed on a per packet basis for flow. If the
modifiable variant of the FAST HBH option is used then intermediate
nodes can change the data inflight.

> Every router on path is going to read/process the IPv6 HBH option. This is also not what is intended.

RFC8200 has relaxed the requirements of RFC2460 so that routers may or
may not process Hop-by-Hop OPtions. draft-ietf-6man-hbh-processing and
draft-ietf-6man-eh-limits make further clarifications to make HBH
practical.

> Only the wireless router acting on behalf on the client, with explicit provisioning (session setup, policy in figure) needs to read.

That's the same expectation we have in FAST. Only an ingress router
into a network is expected to process a ticket in HBH options.

>
>
>
> The difference will be more obvious when (if) we need to consider encrypted metadata.

FAST allows for the signal to be encrypted.

>
> (PS: In this draft, we don’t see the need to encrypt the metadata as the signals are purely advisory and does not leak content or user information.)

Maybe, but for a proposed standard you'll need a strong justification
if that's the answer :-).

>
> However, if we decided that encryption was needed:
>
> With FAST/ IPv6 HBH, the key management is for the Application Domain (AP) to read, not the wireless domain. (otherwise involves complex multi-domain key agreements).

Just like UDP Options, FAST and IPv6 HBH are just carriers of
information. There's no semantics enforced on the content. So any data
that is carried in UDP Options could just as easily be in HBH options.
The difference is about who is permitted to process the information:
UDP Options can only be processed by the destination, HBH options can
be processed by any, all, one, or no nodes in the path.

> With MED, the client to Wireless-CP/Policy signaling can install the MED keys in a simple manner (in 3GPP domain, that would just be small extensions)

That's independent of the information carrier, so the same
infrastructure will work just as easily with HBH options.

>
>
>
> But just to be clear, in the draft, the metadata (MED) and its handling is completely separated from the container/transport (UDP options).

Exactly, that's why HBH options can be substituted for UDP options in
the design with no semantic differences in the content.


>
> If IPv6 HBH  or other transport can evolve to support this kind of handling needed, then the draft can be updated to use MED and that (other) transport.
>
> The key aspect in the draft is the metadata (MED) and how it should be processed on path.

Yes, I like those aspects, and the sentiment that a draft like this
should focus on the semantics and processing of the data aligns with
my view. This draft  is a good use case of host to network signaling,
but there are others like draft-reddy-tsvwg-explcit-signal (which also
proposes to use UDP options as the carrier) and draft-ravi-ippm-csig
(which proposes using L2 to carry the signal). With the potential
benefits of collaboration between applications or hosts and the
network, I believe we are going to see even more proposals. In host to
network signaling, there are two parts: the carrier of the signal, and
the content of the signal. IMO, if we define a common generic and
extensible carrier for host to network signaling, then the various
proposals in the area could focus on the semantics and processing of
the content and not worry so much about the carrier protocol.

Tom




>
>
>
> Regards,
>
> John
>
>
>
>
>
> From: tsvwg <[e-mail]> On Behalf Of [e-mail]
> Sent: Friday, October 27, 2023 5:44 PM
> To: Tom Herbert <tom=[e-mail]>
> Cc: tsvwg <[e-mail]>
> Subject: Re: [tsvwg] Advance notice on request to poll TSVWG for adoption of draft-kaippallimalil-tsvwg-media-hdr-wireless-03
>
>
>
> +1 ;-)
>
> —
>
> Dr. Joe Touch, temporal epistemologist
>
> www.strayalpha.com
>
>
>
> On Oct 27, 2023, at 2:55 PM, Tom Herbert <tom=[e-mail]> wrote:
>
>
>
> On Fri, Oct 27, 2023 at 2:26 PM Spencer Dawkins at IETF
> <[e-mail]> wrote:
>
>
> Dear TSVWG,
>
> We have requested a slot during the IETF 118 meeting to propose that the co-chairs poll the working group for adoption of https://datatracker.ietf.org/doc/draft-kaippallimalil-tsvwg-media-hdr-wireless/, as a basis for further work.
>
> The chairs have given us a 15-minute slot during the Thursday TSVWG session.
>
> Face-to-face meeting time is precious, so we thought it would be helpful if we invited people to look over the draft, and let us know if you see significant impediments to adopting this draft. That would reduce the time we need in the meeting itself.
>
>
> Hi Spencer,
>
> I believe that the use of UDP Options to carry information that is
> processed by intermediate nodes is a significant impediment to
> adoption.
>
>
> From the draft: "The Wireless Node is responsible for forwarding
>
> packets to the Client over the Wireless Network.  The Wireless Node
> inspects metadata but does not alter the UDP option."
>
> There was discussion on the list and I believe that there is general
> consensus that UDP Options are neither designed nor intended to carry
> network layer information like this. They are for carrying End-to-End
> transport layer information.
>
> IMO the proper alternative for carrying network layer information is
> Hop-by-Hop Options like in FAST
> (https://www.ietf.org/archive/id/draft-herbert-fast-04.txt).
>
> Tom
>
>
>
>
>
>
>
> As a reminder,
>
> This draft has been presented at IETF 116, 117 and now 118
> We had considerable discussion at previous IETF meetings and on the TSVWG mailing list
> That feedback has been uniformly helpful, and we've taken it into consideration in the -03 update.
> Adoption has been discussed previously at IETF 117
>
> The updated draft (-03) is described in slides that are uploaded at https://datatracker.ietf.org/doc/draft-kaippallimalil-tsvwg-media-hdr-wireless/
>
> A diff from version -02, discussed at IETF 117, is here: https://datatracker.ietf.org/doc/draft-kaippallimalil-tsvwg-media-hdr-wireless/
>
> Please feel free to follow up on this mailing list, or privately with the document authors.
>
> Best,
>
> Spencer
>
>
>
>