Dale Worley wrote:
Wainwright, John" <[EMAIL PROTECTED]> schrieb am 05.05.05 20:47:21:
If I use "a=sendonly" in the INVITE message when putting a call on hold
what
response should I expect back if the endpoint does not support this attribute ?
Do I still get the 200OK and determine the attribute is not supported by
the
absence of the "a=recvonly" attribute implying I need to fall back to
using
"C=0.0.0.0"
Section 14.2 of RFC 3261 says, in regard to receiving a re-INVITE within an established dialog, "If the new session description is not acceptable, the UAS can reject it by returning a 488 (Not Acceptable Here) response for the re-INVITE. This response SHOULD include a Warning header field."
True. But that is trumpted by SDP requirement to ignore attributes (a=) that are not understood.
I think the only time the answerer would be justified in sending a 488 as consequence of receiving an a=sendonly would be if it understands but doesn't support it. For instance that might make sense for a media player.
An answerer that receives an offer with a=sendonly, if it doesn't understand it, will not understand the concept if directionality based on attributes. So it will think this is a regular offer, and respond with a regular answer. Since it doesn't understand these attributes, it won't have the expected a={recvonly | inactive}. This is an invalid response for an answerer that understands the a=sendonly, but is valid for one that doesn't. So it serves as an indicator that the a=sendonly wasn't understood.
Paul _______________________________________________ Sip-implementors mailing list [email protected] http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
