Polycom Welding System 3725-77601-001H Manual Do Utilizador

Polycom CMA System Operations Guide 

398

Polycom, Inc.

The CMA system has two routing modes.

In this simplest gatekeeper mode, the CMA system gatekeeper resolves IP 

addresses to their E.164 addresses and aliases (similar to the function of a 

domain name server) and grants endpoints permission to place calls. Once the 

gatekeeper performs these two functions, it plays no further role in the call. 

Call signaling and media streams are sent directly between the endpoints in 

the call. 
In Direct mode, the number of concurrent calls supported by a CMA system 

is derived from the number of device licenses at a 3/5 ratio (calls/devices). So, 

for example, a system in Direct mode licensed for 5000 devices supports up to 

3000 calls.
Use Direct mode when implementing a hierarchical architecture. A 

hierarchical architecture is one with multiple gatekeepers, where one 

gatekeeper—the CMA system in Direct mode—acts as the directory 

gatekeeper at the top of the hierarchy. On the directory gatekeeper, you must 

configure all of the other member gatekeepers as neighbors and on the 

member gatekeepers you must configure the directory gatekeeper as a 

neighbor. However, the member gatekeepers do not have to be neighbored 

with each other.
When in Direct mode, some advanced CMA system features do not work. 

These features include Simplified Dialing, Conference on Demand, Alternate 

Routing, Least Cost Routing, MCU board hunting, and firewall traversal for a 

Polycom VBP system in "Enterprise" or "E" mode. (Firewall traversal for a 

Polycom VBP system in "Service Provider or "S" mode does work.) 
The advantage of Direct mode is that conferences stay connected even if the 

gatekeeper fails. 
The disadvantage of Direct mode (along with the loss of advanced 

functionality) is that during a failure and restart the gatekeeper loses track of 

active calls that it was not involved in setting up. In this case, after a failure and 

restart, the gatekeeper’s bandwidth calculations will be incorrect until those 

calls end. Also, since the Conference Monitoring function uses gatekeeper 

data, the monitoring information for those calls may be incorrect or 

incomplete.

In this advanced mode, the CMA system gatekeeper, besides performing the 

functions of a Direct mode gatekeeper, also acts as a proxy for the call 

signaling H.225 messages that set up the call. In this mode, only the media 

streams are sent directly between the endpoints in the call.