Polycom RealPresence 1500 Administrator's Manual page 280

 MGC or RealPresence Collaboration Server can be used on level 2.
Master-Slave Star Cascading Topology
● When creating a cascading link between two RealPresence Collaboration Servers:
 The RealPresence Collaboration Servers operate in CP (Continuous Presence) mode.
● When creating a cascading link between MGCs and RealPresence Collaboration Servers:
 The MGCs can only operate in VSW mode (not supported with Collaboration Server 1800).
The following table summarizes Video Session Modes line rate options that need to be selected for each
conference in the cascading hierarchy according to the cascading topology:
MIH Cascading – Video Session Mode and Line Rate
Topology MCU Type
Level 1 RealPresence
Collaboration Server
Level 2 RealPresence
Collaboration Server
Level 1 RealPresence
Collaboration Server
Level 2 RealPresence
Collaboration Server
Level 1 MGC
Level 2 RealPresence
Collaboration Server
Polycom®, Inc.
Video Session Mode
CP - HD
CP - CIF
CP - CIF 263
CP - CIF 264
Defining Cascading Conferences
Line Rate
1.5Mb/s, 1Mb/s, 2Mb/s
768Kb/s, 2Mb/s
768Kb/s, 2Mb/s
Endpoint
HDX
VSX
HDX, VSX
250