Cisco Cisco Expressway
Appendix 4: Interoperating capabilities and
limitations
limitations
Known interoperating capabilities
Upspeeding from a voice call to a video call
If a voice call is made from a Lync client to a video endpoint registered to Unified CM and then the video
button is selected to enhance the call to a video call, the video endpoint will correctly upspeed to video.
button is selected to enhance the call to a video call, the video endpoint will correctly upspeed to video.
When interworking a Lync client to an H.323 endpoint, the call will only upspeed from voice to video if the
upspeed request occurs before the endpoint sends a BRQ lowering the connection bandwidth.
upspeed request occurs before the endpoint sends a BRQ lowering the connection bandwidth.
Maximum call resolution
The maximum resolution of an SVC to AVC converted call is 720p 30fps.
Known interoperating limitations
Video codecs
If Lync 2010 is used, the video endpoints registered to the Unified CM must support H.263; this is the
common video codec supported by endpoints and the Lync client. (The Lync client does not support H.264.)
common video codec supported by endpoints and the Lync client. (The Lync client does not support H.264.)
The Lync 2010 client for Apple Mac OS X only supports RTVideo, no standards-based video codecs (H.263
or H.264). To make video calls between this client and standards-based video endpoints, a Cisco AM GW is
needed to transcode between RTVideo and H.263/H.264.
or H.264). To make video calls between this client and standards-based video endpoints, a Cisco AM GW is
needed to transcode between RTVideo and H.263/H.264.
Video codec selection
When the B2BUA receives a call with no SDP – that is, without a list of codecs that can be used for the call
(for example, a call that has been interworked from H.323), the B2BUA must populate the SDP with a “pre-
configured” list of codecs from which Lync can select, as Lync does not support INVITES with no SDP.
(for example, a call that has been interworked from H.323), the B2BUA must populate the SDP with a “pre-
configured” list of codecs from which Lync can select, as Lync does not support INVITES with no SDP.
The codecs offered and selected, therefore, may not reflect the best codecs that could have been selected
by the endpoints.
by the endpoints.
MXP endpoints
Video from MXP endpoints to Lync 2013 H.264 SVC is limited to 15fps (video with other endpoints is 30fps).
Joining a Lync conference (AV MCU)
Using a Lync client to invite a third party to join the call does not work if the third endpoint is an endpoint
registered to the Unified CM, or if the endpoint registered to the Unified CM is already in the call and another
Lync client is introduced into the call.
registered to the Unified CM, or if the endpoint registered to the Unified CM is already in the call and another
Lync client is introduced into the call.
This is because when the Lync client invites a third party to join a call, the Lync client tries to create a
conference using Microsoft proprietary messaging (xml in SIP messages), and this is not supported by
standards-based video endpoints.
conference using Microsoft proprietary messaging (xml in SIP messages), and this is not supported by
standards-based video endpoints.
Microsoft Lync and Cisco Expressway Deployment Guide (X8.2)
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Appendix 4: Interoperating capabilities and limitations