ZyXEL Communications MSC1024G Series User Manual page 547

A Context is created when the MGC adds the first Termination to the Context. A Context
is destroyed when the last Termination is removed from the Context.
The following figure shows an example Context, C1. This Context possesses two
Terminations, T1 and T2. T1 is a PSTN connection, and T2 is an IP connection. Because both
Terminations belong to the same Context, they can communicate.
Figure 378 H.248 Connection Example
PSTN
Terminations can move from one Context to another. In the next example, the MG has two
Contexts, C1 and C2. There are currently three active Terminations; T1, T2 and T3. T3 tries
to call T1, but T1 is engaged in a call with T2 (in Context C1). When the call is completed, T1
moves to Context C2 and begins the call with T3 (in this example, the MG must support call
waiting).
Figure 379 H.248 Call Waiting Example
PSTN
Each Termination has the following attributes: "properties", "events", "signals" and
"statistics".
• Properties describe aspects of the Termination (defining it, for example, as representing
an RTP stream).
• Events are call-related occurrences such as off-hook, digits dialed, on-hook, and so on.
Events may trigger messages to the MGC, or may result in action taken by the MG.
MSC1000G/1024G/1224G Series User's Guide
MEDIA GATEWAY
C1
T1
MEDIA GATEWAY
C1
T1
C2
T1
Chapter 18 VoIP
T2
T2
T3
IP
IP
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