Re: Design: Ignored Unknown Frame Types and Intermediaries
Martin Thomson <martin.thomson@gmail.com> Mon, 13 May 2013 21:15 UTC
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Date: Mon, 13 May 2013 14:13:37 -0700
Message-ID: <CABkgnnXJRHu_LsD+Fq9dTNi9Sqfmj0GQMBGO9QzZy6DCfxSJAQ@mail.gmail.com>
From: Martin Thomson <martin.thomson@gmail.com>
To: Roberto Peon <grmocg@gmail.com>
Cc: James M Snell <jasnell@gmail.com>, Yoav Nir <ynir@checkpoint.com>, "ietf-http-wg@w3.org" <ietf-http-wg@w3.org>
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Subject: Re: Design: Ignored Unknown Frame Types and Intermediaries
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On 13 May 2013 11:37, Roberto Peon <grmocg@gmail.com> wrote: > James: > Can you construct a case where, if you follow the rule spelled out in my > earlier email, you fail to achieve interop (because I can't)? It's trivially possible to construct a scenario where this happens, but only if you don't write down a "MUST ignore" rule. Once the rule is in place, then you are constraining future extensibility. A "MUST ignore" rule is the easiest rule to get right, but there are other models you can use. > The rule is, essentially: > If a party to the communication ignores (or removes) something it don't > understand, that must not screw up the session. The ignore/remove distinction is very important. You can't selectively remove; it's all or nothing. Either remove everything you don't know about or leave it all in. This consideration, along with James' hop-by-hop question does suggest a relatively simple way out: All unsupported/unknown frames that have a non-zero stream identifier MUST be ignored. If a stream is forwarded by an intermediary, all unsupported/unknown frames MUST either be forwarded or removed; an intermediary MUST NOT selectively forward unsupported frame types. Unsupported/unknown frames with a zero stream identifier MUST be ignored and MUST NOT be forwarded. > That implies that, when you add anything that must be interpreted, it then > must be declared in the version string (i.e. new version) and thus agreed > upon by both parties up front, and if you don't negotiate that other > version, you don't get to add frames whose removal would screw up the > session. Yeah, we addressed that early on. If you want to guarantee that the other guy is going to support something, either work out how to agree in-session (with those ignored frames) or negotiate a new protocol.
- Re: Design: Ignored Unknown Frame Types and Inter… James M Snell
- Design: Ignored Unknown Frame Types and Intermedi… James M Snell
- Re: Design: Ignored Unknown Frame Types and Inter… Yoav Nir
- Re: Design: Ignored Unknown Frame Types and Inter… Roberto Peon
- Re: Design: Ignored Unknown Frame Types and Inter… Yoav Nir
- Re: Design: Ignored Unknown Frame Types and Inter… James M Snell
- Re: Design: Ignored Unknown Frame Types and Inter… Roberto Peon
- Re: Design: Ignored Unknown Frame Types and Inter… Martin Thomson
- Re: Design: Ignored Unknown Frame Types and Inter… James M Snell
- Re: Design: Ignored Unknown Frame Types and Inter… Roberto Peon
- Re: Design: Ignored Unknown Frame Types and Inter… James M Snell
- Re: Design: Ignored Unknown Frame Types and Inter… Roberto Peon
- Re: Design: Ignored Unknown Frame Types and Inter… Yoav Nir
- Re: Design: Ignored Unknown Frame Types and Inter… Albert Lunde
- Re: Design: Ignored Unknown Frame Types and Inter… Yoav Nir
- Re: Design: Ignored Unknown Frame Types and Inter… James M Snell
- Re: Design: Ignored Unknown Frame Types and Inter… Roberto Peon