gao.yang2@xxxxxxxxxx wrote:
I just find a potential problem of
draft-ietf-sipping-sip-offeranswer-11. I am not sure will you want have
a new version, so I send this discussion offline.
I am working on another version. I am including sipping in my response
so others have the opportunity to comment. (I trust that is ok.)
Section 5.2.5. of draft-ietf-sipping-sip-offeranswer-11:
When the new offer is sent in response to an offerless (re)INVITE,
*all codecs supported by the UA are to be included*, not just the ones
that were negotiated by previous offer/answer exchanges. *The same is*
* true for media types* - so if UA A initially offered audio and video
to UA B, and they end up with only audio, and UA B sends an offerless
(re)INVITE to UA A, A's resulting offer should re- attempt video, by
reusing the zeroed m-line used previously.
While Re-INVITE without Offer:
For codecs, I think the UAS should include as many codecs that the UA is
willing(section 14.2 of RFC3261) to support. I think we should let the
UA has the right to decide which codecs can be use or not for this
current call. At the same time, the UAS should be with responsibility
for failure of session if it cut down the number of codecs. UAS's
willing of codecs can be implemented as local policy or some other forms
of configuration.
Yes, this just requires minor tweak to wording.
Its consistent with the recommendations on sendonly/...
For media types, it is almost the same as codecs, about UA's willing.
But I think we should emphasize on avoiding of introducing new media
types without user's permission, such as just introducing new media
types by equipment or software. Beacause I have met such charging
arguement from users in some operating telecom-network.(If you want the
detail of the charging arguement, I'd like to share it with you).
So, if there is no indication of permission of introducing new media
types from the end user, UAS should just include current using media
types. And if the other side(user of UAC) want to add media types, it
can using another new Offer.
I get your point and agree. Its the same concept - include everything
the UA would be willing to use, not just that which it thinks the peer
wants to use.
Thanks,
Paul
Thanks,
Gao
Section 14.2 of RFC3261:
A UAS providing an offer in a 2xx (because the INVITE did not contain
an offer) SHOULD construct the offer as if the UAS were making a
brand new call, subject to the constraints of sending an offer that
updates an existing session, as described in [13] in the case of SDP.
Specifically, this means that it SHOULD include as many media formats
and media types that the UA *is willing to support*. The UAS MUST
ensure that the session description overlaps with its previous
session description in media formats, transports, or other parameters
that require support from the peer. This is to avoid the need for
the peer to reject the session description.
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