or protocol data units (PDUs), 255 Pbps (petabits per second), 385 Packet radio data networks, 584-586 PBXs (private branch exchanges) Packet-switched networks, 215-243 IP PBXs, 322-323defined, 7 advantages/disadvantages of, 98 network access for, 106-107 ATM, 229-238 open-source PBXs, 323-324 ATM and IP, 238-242 PSTN access services for, 108 circuit switching VS., 99-100 PCM (Pulse Code Modulation), 119, 324 connection-oriented, 84-85, 97, 218 PCS (Personal Communication Services), 587-588 connectionless, 85, 95-97, 218 PDC (Personal Digital Cellular), 567, 592 Frame Relay and, 221-229 PDH (Plesiochronous Digital Hierarchy), 114-123 generations of, 98-99 digital signal hierarchy, 120-123 Internet using, 254 elements of, 115-120 MFA Forum and, 243 overview of, 114 next generation of, 141 standards in, 115 overview of, 215-219 voice compression standards, 119 X.25 and, 219-220 PDPs (policy decision points), 444 Packet switching, 92-93 PDUs (packet or protocol data units), 255 Packet transfer, 192 Peer-to-peer mode, 645 PacketCable, 518-519 Peer-to-peer networking, 478-483 Packets 10GigE, 480-481 defined, 216 defining, 475 IP, 255-256 EFM, 482 overview of, 93-95 with G.SHDSL, 503 PAL (Phase Alternating Line) LANs for, 174 analog TV using, 397 overlay model VS., 483 ATSC DTV standard for, 404-405 overview of, 478-480 requirements for digitized streams, 391 Resilient Packet Ring and other standards, signal degradation in, 390 482-483 Index Peering PLC (powerline communications). See PLT agreements, 294 (powerline telecommunications) defined, 266 Plesiochronous Digital Hierarchy. See PDH Penultimate hop popping, 448 (Plesiochronous Digital Hierarchy) PEPs (policy enforcement points), 444 PLT (powerline telecommunications) Per-trunk signaling, 131 architecture, 530-532 Performance engineering, 706 future of, 532-534 Permanent virtual circuits (PVCs), 10, 225 overview of, 530 Personal area networks (PANs), 149. See also PN (pseudorandom number), 570 WPANs (wireless personal area PoC (Push-to-Talk over Cellular), 700-701