Glossary
GL-6
Cisco ATA 187 Analog Telephone Adaptor Administration Guide for SIP (Version 1.0)
OL-21862-01
SLIC
Subscriber Line Interface Circuit. An integrated circuit (IC) providing central office-like phone
interface functionality.
SOHO
Small office, home office. Networking solutions and access technologies for offices that are not
directly connected to large corporate networks.
T
T.38
T.38 is an ITU recommendation for allowing transmission of fax over IP networks in real time.
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 directly 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 acknowledgments or guaranteed delivery,
requiring that error processing and retransmission be handled 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.