User's Manual
Chapter 5-Cascading Conferences
Polycom, Inc. 5-7
Guidelines
• Content is restricted. When another endpoint wants to send content, the first endpoint 
must stop sending content before the second endpoint can initiate or send content. 
• Endpoints that do not support H.239 can receive the Content using the Send Content to 
Legacy Endpoints option.
• When a participant joins a conference with active Content, content cannot be viewed by 
the new participant. Restart the Content.
• Cascaded MCUs/Gateways must be registered with the same Gatekeeper or 
neighboring Gatekeepers. MCUs and endpoints must also be registered with 
Gatekeepers.
• Gateway/MCU calls require definition of IVR Services. For more information see 
"Defining the IVR Service for Gateway Calls” on page 19-14.
Gateway to Gateway Calls via ISDN Cascading Link
When H.323 participants connects to another IP participants via a Gateway to Gateway call 
over an ISDN link, the dialing string includes the following components:
[GW A prefix in GK] - the prefix with which the Collaboration Server (gateway) is 
registered to the gatekeeper. 
[GW Profile ID] - The ID of the Gateway Profile defined on Gateway A to be used for 
routing the call to the Gateway B.
[GW Profile ISDN/PSTN number] - the dial-in number assigned to the Gateway Profile 
defined on Gateway B, including the required country and area codes.
Information required that is not part of the dialing string:
[Destination number] - the destination number as alias, IPv4 address or ISDN/PSTN 
number of participant B. 
The dialing string format:
H.323 Participants connecting to another IP participant via a Gateway to Gateway call over an 
ISDN link enter a dial string using the format: 
<GW A Prefix in GK><Gateway Profile_ID on GW A>*<Destination ISDN 
Dial-in number assigned to the Gateway Session Profile GW 
B>*<Destination Number, participant>
For example:
GW A prefix in Gatekeeper - (not used with SIP) 22 
Gateway Profile ID in GW A  9999
ISDN Dial-in Number assigned to the
Gateway Session Profile GW B   4444103 
IP Participant Alias     3456
H.323 participant dials: 229999*4444103 and when prompted for the Destination number 
enters 3456 followed by the pound key (#) using DTMF codes.
In version 7.1, H.239 content protocol is H.263 when sent over ISDN or H.323 Cascading link.










