Glossary
GL-6
Cisco ATA 186 and Cisco ATA 188 Analog Telephone Adaptor Administrator’s Guide (H.323)
OL-4008-01
SIP Session Initiation Protocol. Protocol developed by the IETF MMUSIC Working Group as an
alternative to H.323. SIP features are compliant with IETF RFC 2543, published in Ma rch 1999. SIP
equips platforms to signal the setup of voice and multimedia calls over IP networks.
SIP endpoint A terminal or gateway that acts as a source or sink of Session Initiation Protocol (SIP) voice data. An
endpoint can call or be called, and it generates or te rminates the information stream.
SLIC Subscriber Line Interface Circuit. An integrated circuit (IC) providing central office-like telephone
interface functionality.
SOHO Small office, home office. Networking solutions and access technologies for offices that are not
directly connected to large corporate networks.
T
TCP Transmission Control Protocol. Connection-oriented transport layer protocol that provides reliable
full-duplex data transmission. TCP is part of the TCP/IP protocol stack.
TFTP Trivial File Transfer Protocol. Simplified version of FTP that allows files to be transferred from one
computer to another over a network, usually without the use of client authentication (for example,
username and password).
TN power systems A TN power system is a power distribution system with one point connected directl y to earth (ground).
The exposed conductive parts of the installation are connected to that point by protective earth
conductors.
TOS Type of service. See CoS.
U
UAC User agent client. A client application that initiates the SIP request.
UAS User agent server (or user agent). A server application that contacts the user when a SIP request is
received, and then returns a response on behalf of the user. The response accepts, rejects, or redirects
the request.
UDP User Datagram Protocol. Connectionless transport layer protocol in the TCP/IP protocol stack. UDP
is a simple protocol that exchanges datagrams without acknowledgm ents or guaranteed delivery,
requiring that error processing and retransmission be handle d by other protocols. UDP is defined in
RFC 768.
user agent See UAS.
V
VAD Voice activity detection. When enabled on a voice port or a dial peer, silence is not transmitted over
the network, only audible speech. When VAD is enabled, the sound quality is slightly degraded but
the connection monopolizes much less bandwidth.