Zte zxmsg 5200, Техническое руководство

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ZXMSG 5200 (V2.0) Technical Manual
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Communications (H.248 Protocol
Description)
Logic Connection Model
The H.248 protocol use a connection model describing logical entities or
objects that are controlled by MGC in MG. Two abstract concepts are used
in the connection model: Termination and Context.
The termination can initiate/terminate one or more streams. The context
defines topology and connection relations between terminations. A special
context “null context” contains all terminations that have no connection
with other terminations. In the ZXMSG 5200, for example, all idle
subscriber circuits can be terminations in null contexts.
1. Contexts
Context refers to topology and connection relations between multiple
terminations. If more than two terminations are involved in a context,
topology is used to describe the directions of streams among
terminations.
The terminations in null contexts, although not belonging to any
definite context, have their own parameters. MGC can modify and
check the parameters and set events to be checked on terminations.
Generally, the Add command is used to add new terminations to a
context. In adding terminations, if MGC has not defined an existing
context, MG will generate a new context. A termination can quit from a
context by using the Subtract command, or move from one context to
another by using the Move command. A termination can only exist in
one context at a time. When the last termination quits or moves out of
a context, the context will be deleted.
The maximum quantity of terminations in a context is limited by MG.
Those MGs that provide point-to-point connections are allowed a
context having two terminations at most. Those MGs that provide
multipoint conferences can have three or more terminations.
The context has the following attributes:
i.
ContextID
ii.
The topology (who hears/sees whom)
The topology of context describes media stream directions between
terminations in the context. The termination mode (send/receive/_)
on the contrary describes media stream directions at MG’s inlets
and outlets.
iii.
The priority
The priority provides information for MG to process a context
preferentially. MGC also uses the priority to automatically and
smoothly control the priority of traffic in certain circumstances