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Cisco IP Telephony Troubleshooting Guide for Cisco CallManager Release 3.0(1)
© 2000 Cisco Systems, Inc. 7
Glossary
machine, or analog phone attached to a gateway. Examples include
1000, 24231, and so on.
DNIS
Dialed Number Identification Service.
DNS
Domain Name System. System used in the Internet for translating
names of network nodes into addresses.
DRQ
Disengage Request.
DTMF
Dual tone multifrequency. Use of two simultaneous voice-band tones for
dialing (such as touch tone).
Flow
Stream of data traveling between two endpoints across a network (for
example, from one LAN station to another). Multiple flows can be
transmitted on a single circuit.
Full duplex
Capability for simultaneous data transmission from both a sending
station and a receiving station.
G.711
Describes the 64-kbps PCM voice coding technique. In G.711, encoded
voice is already in the correct format for digital voice delivery in the
PSTN or through PBXs. Described in the ITU-T standard in its G-series
recommendations.
G.729
Describes CELP compression where voice is coded into 8-kbps
streams. There are two variations of this standard (G.729 and G.729
Annex A) that differ mainly in computational complexity; both provide
speech quality similar to 32-kbps ADPCM. Described in the ITU-T
standard in its G-series recommendations.
H.225
An ITU standard that governs H.225 session establishment and
packetization. H.225 actually describes several different protocols:
RAS, use of Q.931, and use of RTP.
H.245
An ITU standard that governs H.245 endpoint control.
H.323
Extension of ITU-T standard H.320 that enables videoconferencing over
LANs and other packet-switched networks, as well as video over the
Internet.
Half Duplex
Capability for data transmission in only one direction at a time between
a sending station and a receiving station. BSC is an example of a half-
duplex protocol.
Hookflash
Short on-hook period usually generated by a telephone-like device
during a call to indicate that the telephone is attempting to perform a
dial-tone recall from a PBX. Hookflash is often used to perform call
transfer.
ICCP
Intra-Cluster Control Protocol
ISDN
Integrated Services Digital Network. Communication protocol, offered
by telephone companies, that permits telephone networks to carry data,
voice, and other source traffic.
Jitter
The variation in the arrival times of voice packets.
µ-law (“mu-law”)
Companding technique commonly used in North America. µ-law is
standardized as a 64-kbps codec in ITU-T G.711.
MGCP
Media Gateway Control Protocol. A protocol for Cisco CallManager to
control VoIP gateways (MGCP endpoints).
MTP
Media Termination Point.
Partition
A Partition is a logical grouping of Directory Numbers and Route
Patterns with similar reachability characteristics. For simplicity, these
are usually named for their characteristic, such as "NYLongDistance",
"NY911", etc. When a DN or Route Pattern is placed into a certain
partition, this creates a rule for who can call that device or Route List.
PBX
Private Branch Exchange. Digital or analog telephone switchboard
located on the subscriber premises and used to connect private and
public telephone networks.