Re: p2: Expectation extensions

Amos Jeffries <squid3@treenet.co.nz> Tue, 23 April 2013 13:59 UTC

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Subject: Re: p2: Expectation extensions
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On 23/04/2013 7:22 p.m., Mark Nottingham wrote:
> p2 5.1.1 requires that an unrecognised expectation be replied to with a 417 Expectation Failed.
>
> In my testing, it's fairly common for servers to ignore an unregistered expectation (e.g., "foo").
>
> Given how many problems we already have with Expect, should we consider disallowing further extensions here, and removing this requirement?

So whats gained by making it an expectation if the expectation is 
ignored? nothing.

Removing it also removes the fail-closed property of Expect:. I know the 
property is a great annoyance to new featrue rollout. But it does offer 
the concrete assurance that what is expected is supported which is quite 
useful when designing security related extensions. We have the Prefer 
header coming up to provide the expectation negotiation with fail-open 
semantics.

So overall I think we keep this, the servers not implementing it are 
already non-conformant with Expect.

Amos