Hi Spencer, This is Magnus's charter so I don't want to be expansive in my comments as AD.
I think the next step would be for the WG to come to consensus on this work, whatever that happens to be. My gentle suggestion is that a standards-track design for simultaneous flow on multiple paths is premature, and probably not QUIC-specfiic. However, a short experimental draft to enable this in QUIC would allow the research community to make progress faster. On Thu, Oct 1, 2020 at 7:40 AM Spencer Dawkins at IETF < [email protected]> wrote: > Hi, Martin, > > On Thu, Oct 1, 2020 at 9:21 AM Martin Duke <[email protected]> > wrote: > >> The concerns that Christian and MT raise are the same ones I was alluding >> to, but I do think a draft like this one that adds the necessary bits of >> protocol to enable multipath experimentation is the right scope. I don't >> feel strongly whether we should adopt this and fix it, or fix it and then >> adopt it. >> > > I had asked you and Magnus yesterday what our next steps on multicast > should be. > > Am I reading this correctly as "start working on this draft, on the QUIC > mailing list, and let the working group do the right thing"? > > I'd be fine with that, but wanted to check. > > Best, > > Spencer > > >> Martin >> >> On Thu, Oct 1, 2020 at 1:23 AM Martin Thomson <[email protected]> wrote: >> >>> I share Christian's concerns about the draft, but it's not just ACKs, >>> it's the entire Uniflow concept that I would call into question. >>> >>> On Thu, Oct 1, 2020, at 17:25, Christian Huitema wrote: >>> > I am not sure that the current "mpquic" draft is the right approach. >>> > Specifically, I do not agree that having one packet number space per >>> > path is the right approach. This contradicts the design of QUIC V1, in >>> > which data sent on multiple paths shares a common packet number space. >>> > For example, in QUIC V1, we can start a connection on one path, >>> migrate >>> > to another path, and keep the same packet number space throughout. I >>> > find that a very nice property -- and also an essential property if we >>> > want to support NAT rebinding. Handling multipath with a single number >>> > space requires some book-keeping on the sender side to match >>> > acknowledgements and sending paths, but we have working code for that. >>> > >>> > I am also not convinced that we properly understand the concept of >>> > "path". There is very little in the QUIC V1 protocol that requires >>> > transmission paths to be symmetric: any packet sent from a node to a >>> > valid address of the peer will be accepted, provided the crypto works. >>> > The linkage such requirement comes from the statement that a server >>> > starts directing traffic to a validated path when it sees the client >>> > using the same pair of addresses. This is an "implicit" linkage; I >>> > would expect that the first role of a multipoint extension would be to >>> > replace that by an "explicit" statement of preferences. >>> > >>> > I am worried that we have a set of unresolved security issues around >>> > paths, largely linked to the requirement to support NAT rebinding. If >>> > we support NAT, the IP headers must be outside the authentication >>> > envelope of the crypto. There are plausible attacks in which the >>> > attacker splices a cryptographically valid packet and a forged IP >>> > header. We have some defensive heuristics, but if we study multipath I >>> > hope we will end up with something better. >>> > >>> > -- Christian Huitema >>> > >>> > On 9/30/2020 5:51 PM, Ian Swett wrote: >>> > > Given the responses, can we narrow down the way forward(ideally on a >>> different thread) to directions that are less open-ended? I'll suggest >>> some options, but the chairs and/or ADs need to decide. >>> > > 1) No future work on multipath in the QUIC WG, in the belief the >>> existing connection migration functionality is sufficient. >>> > > 2) Adopt the existing draft as a starting point for QUIC >>> multipath(draft-deconinck-multipath-quic < >>> https://tools.ietf.org/html/draft-deconinck-multipath-quic>), with the >>> explicit goal of not expanding the scope of the document. >>> > > 3) Adopting multipath as a core QUIC WG deliverable. >>> > > >>> > > I favor #2, but these may not be the right options. Normally I'd >>> say people should work this out in person, but that doesn't seem viable at >>> the moment. I'm happy to set up a long(3-4+hr) Google Meet to discuss this >>> via videoconference if that helps move the discussion forward. >>> > > >>> > > Or we can form a design team, which typically takes O(3 months) to >>> finish. >>> > > >>> > > Ian >>> > > >>> > > On Wed, Sep 30, 2020 at 3:15 PM Spencer Dawkins at IETF < >>> [email protected]> wrote: >>> > >> Hi, Martin, >>> > >> >>> > >> Just a couple of thoughts here: >>> > >> >>> > >> On Wed, Sep 30, 2020 at 12:16 PM Martin Duke < >>> [email protected]> wrote: >>> > >>> (Speaking as an individual) >>> > >>> >>> > >>> There is some back-and-forth as to whether these are useful cases >>> are not. I'll take it on faith, given the proponents, that there is a real >>> hope of deploying this. However, I share the desire to not have the WG >>> fully consumed by MP-QUIC for the foreseeable future. >>> > >> >>> > >> That sounds right. I'm assuming that getting the core QUIC >>> specifications published and doing any cleanup work necessary SHOULD/MUST >>> take priority, in the BCP 14 sense of those words. >>> > >> >>> > >> As Lars' initial note said, I'd also like to see the manageability, >>> applicability, and datagram extension working group drafts, already adopted >>> by QUIC, moving forward. >>> > >> >>> > >>> I don't think the community has well-established solutions for >>> many problems in this space (e.g. scheduling). However, I think QUIC is a >>> far better platform for experimentation than the alternatives, and would >>> support a draft similar to draft-deconinck-multipath-quic < >>> https://tools.ietf.org/html/draft-deconinck-multipath-quic> that >>> provided the required protocol extensions to make that happen [1]. >>> > >> >>> > >> I agree that scheduling is challenging - 3GPP is certainly spending >>> time defining different strategies for behaviors, even in addition to the >>> ones we described in >>> https://datatracker.ietf.org/doc/draft-bonaventure-quic-atsss-overview/. >>> > >> >>> > >> And I agree that the QUIC protocol would be a better platform for >>> experimentation than anything I can think of (other suggestions are, of >>> course, welcome). >>> > >> >>> > >>> IIUC the hard, unsolved problems are common to all MP protocols, >>> so I don't think further research and future standards in this area are >>> specific to QUIC or appropriate for the QUIC Working Group. But >>> experimental QUIC extensions would accelerate this work, are appropriate >>> for the WG, and may get us to a place where we could confidently develop >>> standards about it. >>> > >> >>> > >> Targeting Experimental status for work in this area sounds like a >>> fine plan to me (much better than not thinking about multicast in the IETF >>> for a while longer). >>> > >> >>> > >> I know you have a variety of tools at your disposal to direct this >>> work (MP-TCP was done in its own working group, for both Experimental and >>> Standards-Track versions of the protocol specifications). Do the right >>> thing, of course. >>> > >> >>> > >> What do you and Magnus need from members of the community, to help >>> move forward on this? >>> > >> >>> > >> Best, >>> > >> >>> > >> Spencer >>> > >> >>> > >>> Martin Duke >>> > >>> >>> > >>> [1] I would prefer that this draft be Experimental, and have >>> numerous nits about the design that are not relevant to this thread. >>> > >> >>> > >> >>> >>>
