Subject: [PANRG] Multipath protocols for people who aren't running over 5G networks (there may be a few of them)

From: Spencer Dawkins at IETF <[email-masked]>
Date: Thu, 24 Mar 2022 13:01:19 +0100

Dear PANRG,

I had talked with Jen about saying something about this during PANRG, but
thought it better to send this email to the mailing list and give back my
time for other talks.

*Tl;dr: What I'd like to do is to think about how to support the kinds of
capabilities that multipath protocols can rely on 5G core network
infrastructure to support, for multipath operation that isn't part of the
5G Core Network.*

If that's interesting to you, please reply to this email, so we can think
about that together.

More details further down.

Best,

Spencer

*The Too Long Part: *

Now that virtually every transport protocol has at least the beginnings of
a multipath capability, I think it's worth starting to uplevel the
discussion about multipath, and PANRG still seems to be a perfectly
reasonable place to do that.

To take QUIC as one transport with a multipath capability, because I think
the proponents explained this well, the -00 version of
https://datatracker.ietf.org/meeting/112/materials/slides-112-quic-unified-multipath-quic-extension-00
explains that  https://quicwg.org/multipath/draft-ietf-quic-multipath.html
is providing very minimal capabilities that don't even include all of the
capabilities of the three drafts that fed into it.

https://quicwg.org/multipath/draft-ietf-quic-multipath.html#name-high-level-overview
describes these minimal capabilities.

Switching hats for a moment, I think *the QUIC working group is Doing The
Right Thing*, for people with 5G networks, because you would be relying on
a lot of 5G infrastructure to provide guidance to the implementation (for
example, how many connections make sense, and what path selection
strategies make sense), and you don't need additional capabilities in the
definition of Multipath QUIC.

I haven't looked as closely at MP-DCCP, but
https://www.ietf.org/archive/id/draft-ietf-tsvwg-multipath-dccp-04.html#name-operation-overview
makes me think that's also true for MP-DCCP.

And if you think I'm characterizing the various multipath extensions
incorrectly, that's a good thing to say!