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Re: WGLC: p2 MUSTs

From: Roy T. Fielding <fielding@gbiv.com>
Date: Sat, 3 Aug 2013 18:48:22 -0700
Cc: IETF HTTP WG <ietf-http-wg@w3.org>
Message-Id: <6DAAF751-4C18-4A71-AD54-B8338B9B1B47@gbiv.com>
To: Alex Rousskov <rousskov@measurement-factory.com>
On Apr 30, 2013, at 1:46 PM, Alex Rousskov wrote:

>> The CONNECT method requests that the recipient establish a tunnel to
>> the destination origin server [...], until the connection is closed.
> The "until the connection is closed" part is misleading and inaccurate.
> There are two connections in a CONNECT tunnel: (a) between a CONNECT
> sender and CONNECT recipient and (2) between CONNECT recipient the the
> next HTTP hop. The tunnel termination condition is rather complex and is
> detailed later in the same section. It may be a good idea to drop the
> "until..." part. At least I cannot suggest a way to describe it
> correctly as an ending of an already long sentence :-).

Changed to "until the tunnel is closed".

>> When a tunnel intermediary detects that either side has closed its
>> connection, any outstanding data that came from that side will first
>> be sent to the other side and then the intermediary will close both
>> connections. If there is outstanding data left undelivered, that data
>> will be discarded.
> These "will"s should be rephrased as intermediary MUSTs IMO. I also
> suggest moving them higher, before the informal risk discussion.

Moved, fixed, and rephrased to "A tunnel is closed when ..."

>> A client MUST NOT send header fields in a TRACE request containing
>> sensitive data
> The above rule seems too onerous to proxies. Replace "MUST NOT send"
> with "MUST NOT generate"?


>> Use of the 100 (Continue) Status
>> Requirements for HTTP/1.1 clients:
>> ...
>> Requirements for HTTP/1.1 proxies:
> Should we explicitly exclude proxies from the first group of
> requirements by saying "Requirements for user agents" instead of
> "Requirements for clients"?

No, the first set applies to proxies that want to use 100-continue
for their own reasons.

>> MUST contain an updated Max-Forwards field with a value decremented by one (1).
> A lot of proxies violate this MUST because they cannot grok and, hence,
> cannot decrement large integer values. Interoperability problems might
> happen when a client generates Max-Forwards with a maximum value it can
> store (e.g., to count the number of hops to the origin server) but the
> proxy cannot store such a large value (e.g., 64bit vs 32bit).
> Perhaps we can relax this rule by allowing proxies to decrement by "at
> least one", so that a huge value can be replaced with the maximum value
> the proxy can represent?

Changed to

  If the received Max-Forwards value is greater than zero,
  the intermediary MUST generate an updated Max-Forwards field
  in the forwarded message with a field-value that is the lesser of:
  a) the received value decremented by one (1), or
  b) the recipient's maximum supported value for Max-Forwards.

>> A client MUST be prepared to accept one or more 1xx
> Drop "be prepared" to demand acceptance rather than preparedness?

Fixed in prior commit.

>> Proxies MUST forward 1xx responses, unless the connection between the
>> proxy and its client has been closed,
> This "unless" clause should be dropped as implied. Otherwise, we would
> have to add it to every "MUST forward" requirement! :-)


>> A sender MUST generate the IMF-fixdate format when sending an
>> HTTP-date value in a header field.
> Please polish to remove the implication that proxies must fix dates when
> forwarding HTTP-date values. For example: "A sender MUST use the
> IMF-fixdate format when generating a header field containing an
> HTTP-date value".
> Or perhaps simply: "A sender MUST generate HTTP-date values in the
> IMF-fixdate format".


> And here is a list of requirements that are missing an explicit actor on
> which the requirement is placed. Most of these should be easy to
> rephrase to place the requirement on the intended actor (e.g., "A proxy
> MUST" instead of "header field MUST":
>> the content codings MUST be listed in the order in which they were applied


>> then the resource MUST disable or disallow that action

resource owner

>> The Expect header field MUST be forwarded


>> the forwarded message MUST contain an updated Max-Forwards field

Fixed above.

>> The Max-Forwards header field MAY be ignored for all other request methods. 


>> a response with an unrecognized status code MUST NOT be cached.


Committed in

Received on Sunday, 4 August 2013 01:48:47 UTC

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