Re: [tsvwg] Comment on draft-ietf-tsvwg-transport-encrypt

Erik Kline <> Sat, 29 February 2020 00:10 UTC

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From: Erik Kline <>
Date: Fri, 28 Feb 2020 16:10:26 -0800
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To: Spencer Dawkins at IETF <>
Cc: Tom Herbert <>, tsvwg <>
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Subject: Re: [tsvwg] Comment on draft-ietf-tsvwg-transport-encrypt
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It also seems possible that some UDP options ( might come along
that could help things like QUIC effectively have a path-modifiable portion
that (a) isn't a HbH extension header and (b) isn't covered by something
cryptographic that would break if it were modified in-flight.

On Fri, Feb 28, 2020 at 1:03 PM Spencer Dawkins at IETF <> wrote:

> Hi, Tom,
> On Fri, Feb 28, 2020 at 2:31 PM Tom Herbert <
> <>> wrote:
>> While the draft certainly has improved both in tone and content, I
>> still feel like there is one area that is very under-represented.
>> Namely the possibility of using extension headers to carry necessary
>> transport information that the network needs. I have brought this up
>> several times, and don't believe it has been adequately addressed.
>> Section 5 discusses extension headers (in a rather offhand manner). It
> You're talking about Section 5.2, right?
>> is presented in a very negative light focused on the why they won't
>> work. The crux of the argument in the draft is that extension headers
>> are not deployable, RFC7872 is referenced as the basis for that
>> conclusion. But as we pointed out, and even acknowledged in the draft
>> text now, that is from 2016, so the data and questionable. But even if
>> it were still relevant the conclusion drawn from it that EHs are not
>> usable in any form is highly debatable.
>> What the draft fails to mention is that Hop-by-Hop extensions headers
>> are the ONLY protocol conformant way to signal intermediate nodes with
>> data, including transport layer information, other than what is
>> contained in the IP header. Intermediate nodes that parse packets
>> beyond the network layer are not protocol conformant. This is not just
>> an academic purist statement, this is DPI which is what has led to
>> protocol ossification and hence is a primary motivation for transport
>> headers being encrypted in the first place (see QUIC reasoning on
>> this). Extension headers are also being dismissed because of protocol
>> non-conformance in intermediate nodes. As often noted, RFC8200 has
>> relaxed requirements concerning HBH options so that intermediate nodes
>> can ignore. I believe that RFC8200 was published after RFC7828
>> potential impact of that change was not measured.
>> So then one interpretation of the draft is that it is trying to
>> justify one type of protocol non-conformance, on the basis it is
>> useful in practice, yet on the other hand rejects the correct solution
>> to the problem on the because of another type of protocol
>> non-conformance making it not deployable. There seems to be a
>> significant irony at work here.
> ISTM that the draft (if we're talking about 5.2) is talking about
> interdomain use of hop-by-hop extension headers, which might reasonably be
> deployed in a domain that you make decisions about (the subject of 5.1),
> but are (let's say) more challenging to deploy if you're expecting them to
> work between arbitrary endpoints attached to arbitrary domains,
> interconnected over arbitrary topologies.
> I don't disagree with the points you're making, but ISTM that if the
> working group wants to say hop-by-hop extension headers can be a plan, that
> should appear in 5.1, unless someone can point to at least one success
> story of hop-by-hop extension headers being widely deployed and used across
> domain boundaries.
> Best,
> Spencer
>> Tom