[asterisk-users] SIP OPTIONS... Error?

[Alex Balashov]

On 09/19/2011 01:11 PM, Bruce Ferrell wrote:
> On 09/19/2011 09:33 AM, Alex Balashov wrote:
>> Every request needs a From tag.
>>
>
> Uh... OK. Isn't this a From tag:
>
> From: <sip:ping at XX.XX.XX.XX>
>
> Line three of what I send?

No, that's a From URI.

A From tag is a header parameter that is appended to the URI, 
delimited by a semicolon:

    From: <sip:ping at XX.XX.XX.XX>;tag=abc123xyz

Although, RFC 3261 Section 12.1.1 ("UAS behavior") does seem to 
contradict me:

    A UAS MUST be prepared to receive a request without a tag in
    the From field, in which case the tag is considered to have
    a value of null.

However, it goes on to say:

    This is to maintain backwards compatibility with RFC 2543,
    which did not mandate From tags.

In other words, a non-backward-compatible 3261 implementation will 
always generate From tags for all requests.

-- 
Alex Balashov - Principal
Evariste Systems LLC
260 Peachtree Street NW
Suite 2200
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