ZyXEL Communications MSC1024G Series User Manual page 546

Chapter 18 VoIP
Figure 377 H.248 Interface, SCs and MCs
Standby SC
MGC
• The active SC uses the IP address of the H.248 interface to communicate with the MGC.
• Each SC has an IP address for communicating with the MCs (the active SC has one IP
address and the backup SC has a different IP address).
• Each MC has one IP address it uses to communicate with the SC.
18.1.4.1 Media Gateway Terminology
Communication in an H.248 network depends on two concepts contained in the MG:
"Terminations" and "Contexts".
• A Termination is a logical entity representing a connection to a media stream. A
Termination sources and/or sinks connections to the media stream. Every connection to
the MG is uniquely represented by a Termination.
A Termination may represent either a physical connections (such as an analog phone
connection) or an ephemeral connection (such as an RTP stream). Generally, ephemeral
Terminations exist for only as long as they are in use. In contrast, physical Terminations
exist for as long as they are provisioned in the gateway.
Each Termination is assigned a unique identity at the moment of its creation by the MG.
• A Context is a grouping of Terminations. Terminations within the same Context can
intercommunicate. A Termination can belong to only one Context at a time, and Contexts
cannot intercommunicate. Contexts connect two or more Terminations, with the exception
of one - the Null Context. The Null Context contains all physical Terminations not
currently belonging to another Context. Terminations in the Null Context cannot
intercommunicate.
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Backup Media Gateway
Active SC
Media Gateway
IP NETWORK
H.248 signaling
RTP payload
Interface
MSC1000G/1024G/1224G Series User's Guide
MC
MC
MC
MC