vocal VoIP 系统结构

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Table 1-1. VOCAL System Components  
Component
Description
VOCAL System
This is the telephony application.
Figure 1-1
shows an abstract representation of the VOCAL system server modules. A description of each server appears in the next section, see
"Servers"
.
Protocols
The VOCAL system uses several protocols to communicate between its components. The call signaling processes use SIP messaging to communicate internally within the VOCAL system and externally with gateways, translators and IP phones.
For more information about SIP, see
"SIP Overview"
. For more information about the other protocols used in the system, see
"Compatible Protocols"
.
GUI
The graphical user interface (GUI) enables technicians to provision the system, and administrators to set up users and monitor the system's performance. The GUI is web-enabled and requires a Java plug-in to run in a web browser. For more information, see
"Launching the Web Browser"
.
IP Phone
VOCAL supports a variety of phone appliances including SIP phones and SIP User Agent (UA) software applications. SIP phones may be connected to the VOCAL system over any IP network.
Translators
MGCP- and H.323-based appliances require translators to convert their messages into SIP before they can communicate with the VOCAL system.
Gateways
Gateways not only provide entry points between networks, they also provide translation between SIP-based networks and other network types. The VOCAL system works with two types of gateways, the Residential Gateway and the Trunking Gateway.
Residential Gateway
Residential gateways translate analog signals into IP packets, to permit subscribers with analog phone sets/devices to make and receive SIP-based calls.
Trunking Gateway
Trunking gateways permit SIP-based networks to exchange calls with end-points on the PSTN, by providing translation between SIP messages and one of these signal types:

• Analog
  
• Channel Associated Signaling (CAS)
  
• Primary Rate Interface (PRI)

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