RE: Proposal: Run QUIC over DTLS
Lucas Pardue <Lucas.Pardue@bbc.co.uk> Mon, 05 March 2018 23:58 UTC
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From: Lucas Pardue <Lucas.Pardue@bbc.co.uk>
To: Eric Rescorla <ekr@rtfm.com>, IETF QUIC WG <quic@ietf.org>
Subject: RE: Proposal: Run QUIC over DTLS
Thread-Topic: Proposal: Run QUIC over DTLS
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Date: Mon, 05 Mar 2018 23:58:03 +0000
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Hi EKR, This is a very interesting proposal, especially because I have little experience with DTLS. (I also have little experience with QUIC's use of TLS 1.3 so can't comment too strongly in that regard). One aspect of the current QUIC design I like is the separation between key exchange and packet protection. Which allows some alternative use cases. So I read your draft and was not sure if DTLS maintains that possibility or not. Section 6.4 seems to touch on this topic but I wasn't sure if you are asserting the flexibility exists nor or could exist with some work. The link to draft-putman-tls13-preshared-dh "Authenticated Key Agreement using Pre-Shared Asymmetric Keypairs" is quite well aligned to to the use case I was thinking of. It would be nice to leverage such work rather than have to reinvent it for QUIC's current design. Regards Lucas ________________________________ From: QUIC [quic-bounces@ietf.org] on behalf of Eric Rescorla [ekr@rtfm.com] Sent: 05 March 2018 23:05 To: IETF QUIC WG Subject: Proposal: Run QUIC over DTLS Hi folks, Sorry to be the one randomizing things again, but the asymmetric conn-id thing went well, so here goes.... TL;DR. I'd like to discuss refactoring things to run QUIC over DTLS. DETAILS When we originally designed the interaction between TLS and QUIC, there seemed like a lot of advantages to embedding the crypto handshake on stream 0, in particular the ability to share a common reliability and congestion mechanism. However, as we've gotten further along in design and implementation, it's also become clear that it's archictecturally kind of crufty and this creates a bunch of problems, including: * Stream 0 is unencrypted at the beginning of the connection, but encrypted after the handshake completes, and you still need to service it. * Retransmission of stream 0 frames from lost packets needs special handling to avoid accidentally encrypting them. * Stream 0 is not subject to flow control; it can exceed limits and goes into negative credit after the handshake completes. * There are complicated rules about which packets can ACK other packets, as both cleartext and ciphertext ACKs are possible. * Very tight coupling between the crypto stack and the transport stack, especially in terms of knowing where you are in the crypto state machine. I've been looking at an alternative design in which we instead adopt a more natural layering of putting QUIC on top of DTLS. The basic intuition is that you do a DTLS handshake and just put QUIC frames directly in DTLS records (rather than QUIC packets). This significantly reduces the degree of entanglement between the two components and removes the corner cases above, as well as just generally being a more conventional architecture. Of course, no design is perfect, but on balance, I think this is a cleaner structure. I have a draft for this at: https://datatracker.ietf.org/doc/draft-rescorla-quic-over-dtls/ And a partial implementation of it in Minq at: Mint: https://github.com/ekr/mint/tree/dtls_for_quic Minq: https://github.com/ekr/minq/tree/quic_over_dtls I can't speak for anyone else's implementation, but at least in my case, the result was considerable simplification. It's natural at this point to say that this is coming late in the process after we have a lot invested in the current design, as well as to worry that it will delay the process. That's not my intention, and as I say in the draft, many of the issues we have struggled over (headers especially) can be directly ported into this architecture (or perhaps just reused with QUIC-over-DTLS while letting ordinary DTLS do its thing) and this change would allow us to sidestep issued we are still fighting with, so on balance I believe we can keep the schedule impact contained. We are designing a protocol that will be used long into the future, so having the right architecture is especially important. Our goal has always been to guide this effort by implementation experience and we are learning about the deficiencies of the Stream 0 design as we go down our current path. If the primary concern to this proposal is schedule we should have an explicit discussion about those relative priorities in the context of the pros and cons of the proposal. The hackathon would be a good opportunity to have a face to face chat about this in addition to on-list discussion. Thanks in advance for taking a look, -Ekr ---------------------------- http://www.bbc.co.uk This e-mail (and any attachments) is confidential and may contain personal views which are not the views of the BBC unless specifically stated. If you have received it in error, please delete it from your system. Do not use, copy or disclose the information in any way nor act in reliance on it and notify the sender immediately. Please note that the BBC monitors e-mails sent or received. Further communication will signify your consent to this. ---------------------
- Proposal: Run QUIC over DTLS Eric Rescorla
- RE: Proposal: Run QUIC over DTLS Lucas Pardue
- Re: Proposal: Run QUIC over DTLS Ted Hardie
- Re: Proposal: Run QUIC over DTLS Salz, Rich
- Re: Proposal: Run QUIC over DTLS Eric Rescorla
- Re: Proposal: Run QUIC over DTLS Eric Rescorla
- Re: Proposal: Run QUIC over DTLS Mark Nottingham
- Re: Proposal: Run QUIC over DTLS Eric Rescorla
- Re: Proposal: Run QUIC over DTLS Ian Swett
- Re: Proposal: Run QUIC over DTLS Kazuho Oku
- Re: Proposal: Run QUIC over DTLS Subodh Iyengar
- RE: Proposal: Run QUIC over DTLS Hannes Tschofenig
- RE: Proposal: Run QUIC over DTLS Mikkel Fahnøe Jørgensen
- Re: Proposal: Run QUIC over DTLS Kazuho Oku
- Re: Proposal: Run QUIC over DTLS Marten Seemann
- Re: Proposal: Run QUIC over DTLS Mirja Kühlewind
- RE: Proposal: Run QUIC over DTLS Lubashev, Igor
- RE: Proposal: Run QUIC over DTLS Lucas Pardue
- Re: Proposal: Run QUIC over DTLS Patrick McManus
- Re: Proposal: Run QUIC over DTLS Eric Rescorla
- Re: Proposal: Run QUIC over DTLS Christian Huitema
- Re: Proposal: Run QUIC over DTLS Eggert, Lars
- Re: Proposal: Run QUIC over DTLS Roberto Peon
- RE: Proposal: Run QUIC over DTLS Mike Bishop
- Re: Proposal: Run QUIC over DTLS Eric Rescorla
- Re: Proposal: Run QUIC over DTLS Christian Huitema
- Re: Proposal: Run QUIC over DTLS Victor Vasiliev
- Re: Proposal: Run QUIC over DTLS Subodh Iyengar
- Re: Proposal: Run QUIC over DTLS Ted Hardie
- Re: Proposal: Run QUIC over DTLS Martin Duke
- Re: Proposal: Run QUIC over DTLS Benjamin Kaduk
- Re: Proposal: Run QUIC over DTLS Phillip Hallam-Baker
- Re: Proposal: Run QUIC over DTLS Brian Trammell (IETF)
- RE: Proposal: Run QUIC over DTLS Hannes Tschofenig
- Re: Proposal: Run QUIC over DTLS Christopher Wood
- Re: Proposal: Run QUIC over DTLS Brian Trammell (IETF)
- Re: Proposal: Run QUIC over DTLS Leif Hedstrom
- RE: Proposal: Run QUIC over DTLS Gabriel Montenegro
- Re: Proposal: Run QUIC over DTLS Christian Huitema
- Re: Proposal: Run QUIC over DTLS Eric Rescorla
- Re: Proposal: Run QUIC over DTLS Mirja Kühlewind
- Re: Proposal: Run QUIC over DTLS Ted Hardie
- Re: Proposal: Run QUIC over DTLS Eric Rescorla
- Re: Proposal: Run QUIC over DTLS Mikkel Fahnøe Jørgensen
- Re: Proposal: Run QUIC over DTLS Ted Hardie
- Re: Proposal: Run QUIC over DTLS Brian Trammell (IETF)
- Re: Proposal: Run QUIC over DTLS Philipp S. Tiesel
- Re: Proposal: Run QUIC over DTLS Mark Nottingham
- Re: Proposal: Run QUIC over DTLS Eric Rescorla