Glossary E-7
DDS (Digital Data Service)
An AT&T dial-up data service offering for 2.4 to 56 Kbps over subscriber loop cable. Requires
a Data Service Unit, DSU, at customer premise for interface to the DDS trunk.
Device Code
The first 8 bits of a FastPacket Address.
DFM (Data Frame Multiplexing)
An optional feature that saves data channel bandwidth by analyzing data channel content and
suppressing repetitive data patterns.
Dial Access Switching
Another name for the INS Dial-Up Frame Relay application.
Dial-Up Frame Relay
An INS application that uses a DAS Server Shelf and software to enhance Cisco WAN switching
networks with frame relay soft permanent virtual circuits (SPVCs) for dial-up dial-backup
connections.
DLCI (Data Link Connection Identifier)
A field in a frame relay data packet that identifies the destination for the data.
domain
A grouping of nodes sharing common interests or attributes.
domain name
A unique name consisting of the letter “D” immediately followed by a number (1–8) delineated
by a “.” (period) from the node name (1–8 characters maximum). Example: D1.alpha.
domain number
A number from 1–8 assigned with the cnfdmn command. The number assigned is part of the
domain name.
DPNSS
Digital Private Network Signalling System. A common-channel message-oriented signalling
protocol commonly used by private branch exchanges (PBXes). The INS Voice Network
Switching application supports DPNSS signalling.
DS0 (Digital Signal 0)
A 64 Kbps channel used to transmit encoded voice and/or data. There are 24 DS0 channels in a
circuit T1 (DS1) line. DS0 data is transmitted using one or more DS0 circuits in a T1 or E1 circuit
line.
DS0A
An extension of DS0 that defines the format for assembling various low-speed data circuits (1.2
to 19.6 Kbps) into a single 64 Kbps DS0 channel.
DS1 (Digital Signal 1)
A digital transmission standard that carries 24 individual channels in a bipolar, high-speed line
signal at 1.544 Mbps. DS1 signal level is 3V.
