Re: [sipcore] Reason as a parameter rather than an escaped header

Paul Kyzivat <pkyzivat@cisco.com> Thu, 11 November 2010 14:59 UTC

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Date: Thu, 11 Nov 2010 23:00:02 +0800
From: Paul Kyzivat <pkyzivat@cisco.com>
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To: "Worley, Dale R (Dale)" <dworley@avaya.com>
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Subject: Re: [sipcore] Reason as a parameter rather than an escaped header
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inline

On 11/11/2010 5:09 PM, Worley, Dale R (Dale) wrote:

> But it looks like we need to continue this hack for compatibility.  So let us:
> - publicly state this is a hack
> - not repeat the mistake in other cases

yep

>>> The Reason header is intended to tag the Reason why the hi-targeted-to
>>> URI was retargeted and thus it goes with the "old" hi-entry versus the
>>> "new" one.
>>
>> Just stating it that was exposes the problem.
>> The intent of the Reason header is specified in RFC3326.
>> Any use that isn't consistent with that is an abuse.
>> Its intended to indicate why a *request* is being sent.
>
> Yes, but it quickly mutated into a carrier in responses to provide
> additional information as to why the response was generated.
> Consider:
>
>     draft-jesske-dispatch-reason-in-responses-02

1 - quickly? The Reason header is old.
2 - did I miss something? what is the status of the jesske draft?
     isn't it still just an individual draft?

>> So then we allow it continue to metastasize, e.g. by defining new Reason
>> values that aren't ever expected to be used in requests, and that
>> wouldn't make any sense if they were?
>
> That seems likely.  It's probably a good thing.  It's a bit sketchy to use
> the same header to describe why a request was generated and also why
> a response was generated, but it's not going to cause confusion.

I disagree its a good thing.

If we need new response codes we can define them, so we shouldn't in 
general need new response codes to clarify response codes.

Perhaps the Q.850 stuff is a special case since we are there relating 
things from a different and independent namespace. Even then its a bit dicy.

But my point wasn't reasons for requests vs. reasons for responses. It 
was about reasons for requests vs. reasons for H-I entries. And IIUC the 
reasons in Marianne's draft are *not* reasons for responses. They are 
reasons for retargeting, generally without there having been any 
response. They are indeed a reason for a request. And it is a reason for 
the request with the new target, not the reason for the request with the 
old target.

	Thanks,
	Paul