8 uplink service classes, 354-355 trap manager, 560 upper-layer protocols (ULPs), 323, 325. See also trap messages, 560 ULP entries Trap verb, 557 upper sideband, 81 traveling-wave tubes (TWTs), 222 upright (erect) sideband, 81 tree network, 292, 294f upstream services, 448, 450 tree structure, 310 impairments related to, 451 ILMI ATM UNI MIB, 571f usable bandwidth, 273 tributary unit group (TUG), 504 usage/network parameter control (UPC/NPC), 532 tributary unit-n (TU-n), 503-504 User Datagram Protocol (UDP), 556 troubleshooting, network, 542-544 user-network interface (UNI), 516, 517f, 522 trunk amplifiers, 439 ATM, 514-516 coaxial cable, 437 ATM layering at, 522, 523 trunk-dimensioning information, 61, 62 ILMI functions for, 568-569 trunk facilities, return loss on, 103 user parts, 364 trunk gateway, 398 CCITT Signaling System No. 7, 381-384 trunk-group overload, 551 user plane (U-plane), 516, 522 INDEX VarBindList, 558 of, 388-389 Variable Binding field, in SNMP messages, 558 media gateway controller and, 395-400 variable bit rate (VBR) service, 512 voice telephony, impulse noise and, 50 variance, 60 voice telephony transmission, 89-105 VC cross-connect, 528 subscriber loop design, 93-102 velocity of propagation, 97. See also propagation telephone subset operation, 91-93 velocity VF repeaters (amplifiers), 103-104 of radio waves, 25 voice channel definition, 90-91 verbs, 557 voice traffic, intensity of, 89 Version field, in SNMP messages, 557 voice transmission vertical lines, 422 as a QoS parameter, 42-44 vertical redundancy checking (VRC), 255 quantization in, 112-113 vertical scanning generator, 408-409 VoIP data traffic, 89. See also voice over IP (VoIP) vertical synchronizing pulses, 408-409 VoIP gateway, 390-392 very-small-aperture terminal (VSAT) networks, functions of, 391 229-231 voltage, 576 topology of, 230f in ac circuits, 594-596 very-small-aperture terminal systems, 197 in closed circuit, 578-579 VF (voice-frequency) channel, 90 decibels and, 621-623 VF repeaters/amplifiers, 101 polarity, 166 VF 