Chapter 1
Product Overview
SIP Clients
SIP clients include:
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SIP Servers
SIP servers include:
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What Is the Cisco SIP IP Phone?
Cisco SIP IP phones are full-featured telephones that can be plugged directly into an IP network and can
be used very much like a standard private branch exchange (PBX) telephone. The Cisco SIP IP phone is
an IP telephony instrument that can be used in VoIP networks.
The Cisco SIP IP phone model terminals can attach to the existing data network infrastructure, via
10BASE-T/100BASE-T interfaces on an Ethernet switch. When used with a voice-capable Ethernet
switch (one that understands type of service [ToS] bits and can prioritize VoIP traffic), the phones
eliminate the need for a traditional proprietary telephone set and key system and PBX.
The Cisco SIP IP phone complies with RFC 2543.
OL-2206-01
Phones—Can act as either a UAS or UAC. Softphones (PCs that have phone capabilities installed)
and Cisco SIP IP phones can initiate SIP requests and respond to requests.
Gateways—Provide call control. Gateways provide many services, the most common being 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 codecs and performs call setup and
clearing on both the LAN side and the switched-circuit network side.
Proxy server—The proxy server is an intermediate device that receives SIP requests from a client
and then forwards the requests on the client's behalf. 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—Receives SIP requests, strips out the address in the request, checks its address
tables for any other addresses that may be mapped to the one in the request, and then returns the
results of the address mapping to the client. Basically, redirect servers provide the client with
information about the next hop or hops that a message should take and then the client contacts the
next hop server or UAS directly.
Registrar server—Processes requests from UACs for registration of their current location. Registrar
servers are often co-located with a redirect or proxy server.
What Is the Cisco SIP IP Phone?
Cisco SIP IP Phone Administrator Guide Version 3.0
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