[SIPForum-discussion] Allow Header usage

[vijay baskar]

Hi,

Is the Allow header is mandatory in INVITE and 200 OK, after reading the RFC
it looks like it is mandatory.
But there are some UA still accepting the INVITE/200 OK without Allow
header.

Please clarify.



>From RFC 3261:

 13.2.1 Creating the Initial INVITE
*Since the initial INVITE represents a request outside of a dialog, its
construction follows the procedures of **Section 8.1.1. Additional
processing is required for the specific case of INVITE. An Allow header
field (Section **20.5) SHOULD be present in the INVITE. It indicates what
methods can be invoked within a dialog, on the UA **sending the INVITE, for
the duration of the dialog. For example, a UA capable of receiving INFO
requests within **a dialog [34] SHOULD include an Allow header field listing
the INFO method. ** *
* *
13.3.1.4 The INVITE is Accepted
 *The UAS core generates a 2xx response. This response establishes a dialog,
and therefore follows the **procedures of Section 12.1.1 in addition to
those of Section 8.2.6. A 2xx response to an INVITE SHOULD **contain the
Allow header field and the Supported header field, and MAY contain the
Accept header field. ** *


Thanks in advance.

BRs
Vijay
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