Samsung Ubigate iBG3026 Configuration Manual page 381

From an architectural standpoint, the physical components of a SIP network
can be grouped into two categories: clients(endpoints) and servers. Figure 28.1
illustrates the architecture of a SIP network.
1.
SIP Client
Phones
−
Gateways
−
2.
SIP Server
Proxy server
−
Redirect server
−
Registrar server
−
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User agent which can attempt or receive a call voluntarily.
Intermediary entity which can perform a translation function between
SIP conferencing endpoints and terminals of other type.
A gateway performs the translation between transmission formats and
translation between communications procedures. In addition, the
gateway translates between audio and video codecs and performs call
setup and clearing on both the LAN side and the switched-circuit
network side.
An intermediary entity that acts as both a server and a client for the
purpose of making requests on behalf of other clients. Proxy servers
can provide functions such as authentication, authorization, network
access control, routing, reliable request retransmission, and security.
A user agent server that provides the client with information about the
next hop or hops that a message should take and then the client
contacts the next-hop server directly.
A server that accepts REGISTER requests and places the information it
receives in those requests into the location service for the domain it
handles. Registrar servers are often co-located with a redirect or proxy
server.
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