GL-3
Cisco IP Phone Models 7905G and 7912G Administrator Guide (SIP)
OL-4277-01
Glossary
compression
The running of a data set through an algorithm that reduces the space required
to store or the bandwidth required to transmit the data set. Compare with
companding and expansion.
CoS
Class of service. An indication of how an upper-layer protocol requires a
lower-layer protocol to treat its messages. In SNA subarea routing, CoS
definitions are used by subarea nodes to determine the optimal route to establish
a given session. A CoS definition comprises a virtual route number and a
transmission priority field. Also called ToS.
D
DHCP
Dynamic Host Configuration Protocol. Provides a mechanism for allocating IP
addresses dynamically so that addresses can be reused when hosts no longer
need them.
dial peer
An addressable call endpoint. In Voice over IP (VoIP), there are two types of
dial peers: POTS and VoIP.
DNS
Domain Name System. System used on the Internet for translating names of
network nodes into IP addresses.
DSL
Digital subscriber line. Public network technology that delivers high bandwidth
over conventional copper wiring at limited distances. There are four types of
DSL: ADSL, HDSL, SDSL, and VDSL. All are provisioned via modem pairs,
with one modem located at a central office and the other at the customer site.
Because most DSL technologies do not use the whole bandwidth of the twisted
pair, there is room remaining for a voice channel.
DSP
Digital signal processor. Specialized hardware and software algorithms that
perform complex processing of digitized data that was originally analog data.
Typically segments a voice signal into frames and stores the frames in voice
packets.
DTMF
Dual tone multifrequency. A type of signaling that combines two distinct
frequencies to generate a tone for each digit or character dialed, which is used by
customers to signal the network. Sometimes referred to as “touchtone,” because a
customer generally touches keypad keys to generate the tones.
