SI reference model, 165-168 ers), 105-106 prerequisites for, 3-4 DCSs (digital cross-connect) systems TCP/IP four-layer reference model, 168-171 backbone for WANs, 211 Data communications equipment (DCE), 152-154, features of, 88 overview of, 118-119 Data competitive local exchange carriers SDH/SONET, 128-129 (DCLECs), 105-106 DDSs (digital data services), 205-206 Data Encryption Standard (DES), 376 Dedicated network connections, 11 Data eyeglasses, xlviii-xlix Defense Advanced Research Projects Agency Data flow (DARPA), 248 asynchronous/synchronous transmission, Defense Research and Engineering Network 162-164 (DREN), 279 coding schemes, 160-162 Deficit Round Robin (DRR), 297-299 DTE and DCE in, 152-154 Delay. See Latency error control in, 164-165 Demarcation point, 107 modems and modulation in, 154-159 Dense Wavelength Division Multiplexing. See physical interface in, 152-154 DWDM (Dense Wavelength Division simplex, half-duplex, and full-duplex transmis- Multiplexing) sion, 159-160 Department of Defense (DoD), 279 transmission channel in, 152-154 DES (Data Encryption Standard), 376 Data link layer protocols, OSI, 168 Designated router (DR), OSPF, 261 Data networking. See Data communications Deterministic technique, 183 Data Over Cable Service Interface Specifications. Diabetes infusion pump implant, xlii See DOCSIS (Data Over Cable Service Inter- Dialup users, Internet, 285-286 face Specifications) DIAMETER protocol, 375, 421 Data rates Dickson, W. K. L., 398 802.11a and 802.11g, 645 DID (direct inward dialing) trunks, 108 GEO satellites, 67 Differential Binary PSK (DBPSK), 644 twisted-pair, 51 Differential Phase-Shift Keying (DPSK), 562 ZigBee, 673 Differential Quadrature PSK (DQPSK), 644 Data service, 202 Diffie-Hellman algorithm, 379 Data service units (DSUs), 205-206, 288 DiffServ (Differentiated Services) Data storage grids, lii defined, 299 Data terminal equipment (DTE), 152-154, 202 overview of, 300-301 Datagram Congestion Control Protocol (DCCP), VoIP QoS and, 329-330 VPN QoS and, 357 Datagrams, 96, 169