Accton Technology SIP Gateway VG3300 Series - Manual (Page 8)

VG3300
series user guide
SIP Clients
SIP clients include the following:
Phones—Can act as either a UAS or UAC. Soft phones (PCs that have phone capabilities installed)
and SIP IP phones can initiate SIP requests and respond to requests.
Gateways—Provide call control. Gateways provide much functionality. The most common one is a
translation function between SIP conferencing endpoints and other terminal types. This function
includes translation between transmission formats and between communications procedures. In
addition, the gateway also translates between audio and video Codec and performs call setup and
clearing on both the LAN side and the switched-circuit network side.
SIP Servers
SIP servers include the following:
Proxy server—The proxy server is an intermediate device that receives SIP requests from a client
and then forwards the requests on behalf of the client's. Basically, proxy servers receive SIP
messages and forward them to the next SIP server in the network. Proxy servers can provide
functions such as authentication, authorization, network access control, routing, reliable request
retransmission, and security.
Redirect server—Provides the client with information about the next hop or hops that a message
should take, then the client contacts the next hop server or UAS directly.
R egistrar server—Processes requests from UACs for registration of their current location. Registrar
servers are often co-located with a redirect or proxy server.
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