The choice of which response to generate to reject a call is a conscious
decision on the part of the implementer depending on how he wants the
rejection to be perceived by the caller.
A 486 is used when the *goal* is for the caller to be informed that the
callee is busy.
A 480 can be used so that the caller will think the callee isn't there.
And a 603 is used to signal an explicit rejection. (It also, arguably,
terminates any other forks, which may be a desirable feature for the
callee.)
Its not hard to imagine a phone with buttons for all three of these.
Paul
Iñaki Baz Castillo wrote:
> Hi, SIP response codes for rejecting a call is a pain, each implementator
> does
> a different thing. RFC 3261 doesn't help a lot with the ambiguity of
> 480/486/603 codes.
>
> In fact, when the user rejects explicitely a call (by pressing "Reject"
> button) some UA's generate a "480 Temporarily Unavailable" (as SJphone,
> Thomson S2030), others generate a "486 Busy Here" (as X-Lite, Siemens), and
> others a "603 Decline" (as Twinkle).
>
> Personally I don't understant why "486 User Busy" is used for rejecting a
> call.
> Also, the use of "6XX" is not good since the UAS cancels the other ringing
> UAS
> (in case of parallel forking) what it's not good in many cases.
>
> So there is a "draft" [1] suggesting the use of "441 Decline". IMHO this MUST
> exist in the original RFC 3261. The absence of it has generated the actuall
> situation in which each implementator rejects a call in a different way.
>
> So... why this draft is still a draft?
>
> draft-worley-6xx-considered-harmful
> http://tools.ietf.org/html/draft-worley-6xx-considered-harmful-00
>
> Thanks for any explanation.
>
>
>
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