External SBC Device Management
Polycom, Inc. 127
On the External SBC page, you can add or remove H.323 SBC (session border
controller) units (Polycom VBP appliances are supported) from the list of such
devices that the system can use. In an H.323 environment, H.323 SBCs regulate
access across the firewall.
This is a supercluster-wide configuration.
For most configurations, H.323 SBCs should be configured on a per site basis
on the Sites page. There are three reasons to configure an H.323 SBC on the
External SBC page:
•To create a prefix service that allows dialing through the specific SBC by
prefix.
•To define a postliminary script to be applied when dialing through the
SBC.
•For bandwidth management.
The Polycom DMA system is capable of performing call admission control
(CAC) while processing an LRQ from a neighbor gatekeeper. This allows
the system to reject the call for resource or policy reasons early in the setup
process (in response to the LRQ), rather than waiting until later in the call
setup.
In order to perform early CAC, the Polycom DMA system must know the
caller’s media address, which isn’t provided in the LRQ and is
unknowable for an ordinary gatekeeper. If the gatekeeper is also an SBC,
however, it proxies the media. The Polycom DMA system can assume that
its media address is the same as its signaling address, and proceed with
early CAC. The Polycom DMA system performs early CAC only in
response to LRQs received from SBCs configured on the External SBC
page.
The following table describes the fields in the list.
Note
This page is only for H.323 SBCs. SIP SBCs are configured as SIP peers. See
“External SIP Peer” on page108.
Table 5-23 Fields in the External SBC list
Column Description
Name The name of the SBC.
Description Brief description of the SBC.
Address Host name or IP address of the SBC.