B-17
Appendix B: Glossary
DSX Hierarchy Digital Signal X. The signal hierarchy used with T-carrier systems.
Table G-2. Digital Signal X (DSX) hierarchy
DSX-1 Digital Signal X-1. A 1.544 Mbps T1 connection.
DTE Data Terminal Equipment. A device that controls data flowing to or from a
computer. On a Frame Relay network, the DTE receives data from the LAN in
the form of multiple protocol packets and encapsulates each packet into a
Frame Relay frame. The header of such a frame is called the Data Link
Connection Identifier (DLCI) and contains the frame’s ultimate destination.
See also DCE.
DTMF Dual Tone Multi-Frequency. The signal to the phone company that is generated
when ordinary telephone touch keys are pressed. In the United States, this is
known as “touch-tone” dialing.
DVB Digital Video Broadcasting. A suite of internationally accepted, open
standards for digital television maintained by the DVB Project, an industry
consortium with more than 300 members. The DVB standards use current,
existing satellite, cable and terrestrial infrastructures.
DVMRP Distance Vector Multicast Routing Protocol. An OSI Layer 3 multicast routing
protocol for use within a single AS. DVMRP generates a multicast routing table
and forwards packets accordingly. It uses Internet Group Management
Protocol (IGMP) messages to exchange information with other routers. For
more information, see RFC 1075 (at http://www.ietf.org/rfc/rfc1075.txt).
DWDM Dense Wavelength Division Multiplexing. A technology that puts data from
different sources together on fiber optic. Each signal is carried on its own
separate light wavelength, and up to 80 (and theoretically more) separate
wavelengths or channels of data can be multiplexed into a lightstream trans-
mitted on a single optical fiber. In a system with each channel carrying 2.5
Physical
carrier
DSD DSX interface DSO multiple T1 multiple Transmission
rate
— DS0 — 1 — 64 Kbps
T1 DS1 DSX-1 24 — 1.544 Mbps
T2 DS2 DSX-2 96 4 6.312 Mbps
T3 DS3 DSX-3 672 28 44.736 Mbps
T4 DS4 DSX-4 4032 168 274.176 Mbps
T5 DS5 DSX-5 8064 336 560.160 Mbps
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