Table 3 says:
Require ar - c - c c c
where
c: Conditional; requirements on the header field depend on the
context of the message.
In your case, 421 satisfy this conditional requirement. Thus, the
Require header may be present in response/request based on the
context.
I do not think the RFC has contradicted the MUST requirement for 421
response. It has just take a generalized approach for making this
table entry for Require header.
I do not think this table is that elaborate to accommodate every
possible case and in which case, there would have been no significance
for "c" symbol.
Thus, you have to consider this table and the rest of the RFC content
for validation.
On Wed, May 6, 2009 at 9:09 AM, Ravi Kumar <[email protected]> wrote:
> Hi,
>
> Thanks for response for the last query.
>
>
> I have doubt about the table 3 uses. As per the section 21.4.16 421
> Extension Required
> The UAS needs a particular extension to process the request, but this
> extension is not listed in a Supported header field in the request.
> Responses with this status code MUST contain a Require header field
> listing the required extensions.
>
> And table 3 mention that this header field may present in all the request
> and response.
>
> So the sip entity should validate request or response based on the table 3
> or MUST clause in rfc. Because here seems some conflict between the table 3
> and the section 21.4.16.
> Because this is one place I have found different behavior in rfc.
> Please correct me if I am wrong.
>
> Thanks & Regards,
> Ravi Kumar
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>
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