Cisco Cisco Expressway
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Screen share transcoding loads the CPU more heavily than video (AV) calls. Testing shows that CPU load
increases in a roughly linear way when increasing the number of transcode sessions. There is a similar
characteristic when increasing the number of AV calls without screen sharing, so you should be able to get
more shares if the Expressway is processing fewer concurrent AV calls overall.
increases in a roughly linear way when increasing the number of transcode sessions. There is a similar
characteristic when increasing the number of AV calls without screen sharing, so you should be able to get
more shares if the Expressway is processing fewer concurrent AV calls overall.
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Higher resolutions and/or multiple monitors also affect performance. The transcoder will output the same
resolution that it receives from Lync, up to a maximum resolution of 1920x1200. Beyond that, the transcoder
will scale the shared screen down to fit within 1920x1200. If the received resolution exceeds 3840x2160, the
transcoder crops the screen to fit within that resolution before scaling it down. The transcoder will also scale
down if it needs to respond to constraints on resources, for example, bandwidth limitations.
resolution that it receives from Lync, up to a maximum resolution of 1920x1200. Beyond that, the transcoder
will scale the shared screen down to fit within 1920x1200. If the received resolution exceeds 3840x2160, the
transcoder crops the screen to fit within that resolution before scaling it down. The transcoder will also scale
down if it needs to respond to constraints on resources, for example, bandwidth limitations.
Screen Sharing Deployments
The following deployments support screen sharing from Lync:
Figure 2 Lync environment to conference managed by TelePresence Conductor trunked to Unified CM
Figure 3 Lync environment to SIP endpoint registered to Unified CM
Notes:
1.
If you are using the Optimize Resources feature with Lync screen sharing, you need TelePresence Conductor
version XC4.0 or later.
version XC4.0 or later.
2.
If you are using the Optimize Resources feature with Lync screen sharing, you need TelePresence Server
version 4.2 or later.
version 4.2 or later.
3.
Requires Cisco VCS Control for H.323 registrations, not shown in the diagram.
Video Codecs
If you use Lync 2010 for Windows, the other video endpoints must support H.263; this is the common video codec
supported by endpoints and the Lync client. (Lync 2010 for Windows does not support H.264)
supported by endpoints and the Lync client. (Lync 2010 for Windows does not support H.264)
The Lync 2010 client for Apple Mac OS X only supports RTVideo. It does not support H.263 or H.264. To make video
calls between this client and Cisco Collaboration video endpoints, you need the Cisco AM GW to transcode between
RTVideo and H.263/H.264.
calls between this client and Cisco Collaboration video endpoints, you need the Cisco AM GW 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.
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.
endpoints.
Conferencing
Cisco TelePresence Server
Supported Lync clients can join conferences hosted on a TelePresence Server.
The TelePresence Server must be trunked to Unified CM or controlled by a TelePresence Conductor that is trunked to
Unified CM.
Unified CM.
9
Cisco Expressway with Microsoft Lync Deployment Guide
Introduction