working, 156-158 DID number portability, 88-89 endpoints, 143 emergency call routing, 93-94 enhanced services, SIP trunking for geographic boundaries, 89 SP networks, 70 high availability, 93 Enterprise deployments IP addressing, 95 connecting to SP, case study, 263-274 operational implications, 92 endpoints oversubscription, containing, 90 cellular phones, 18-19 QoS considerations, 91 desktop handsets, 15-16 regulatory considerations, 90 effects on SIP trunks, 19 DNS SRV records, load balancing, 134-136 softphones, 16-17 documentation, SBC vendor technical WiFi phones, 17-18 requirements, 182 session management, 77 DSPs (digital signal processors), 3, 48 SIP trunking solutions, 20-24 DTMF (dual-tone multi-frequency), application interconnection 148-150 SBC, 78-79 DTMF interworking, 107, 271-272 Enterprise session DTMF relay, 149-150 management, 77 dual digit drop, configuring, 239 IME, 79 interconnecting SBC, 76 IP networks, 77 equipment, capital costs, 47-49 Ethernet switches, 6 316 evaluating available SIP trunk offerings evaluating available SIP trunk IPv6 effect on, 307 offerings, 248 required technological changes, call load balancing, 251 304-307 DID porting realities, assessing, 249-251 emergency call handling, 251 failover rating, 251 Gates, Bill, 304 geographic coverage, identifying, geographic coverage, identifying, 249 geographic design considerations, network demarcation, identifying, geographical redundancy, 131 physical SIP trunk delivery, 251 global CAC, 126-127 provider offerings, assessing, 249 goals of UC, required technological TDM-equivalent feature availability, changes, 304-307 identifying, 249-250 Green revolution, impact on UC, 308 troubleshooting procedures, specifying, 252 executing trial plan, 254-255 expertise, cost of, 54 H.323, interconnecting with SIP, 270- handsets, 15-16 headquarters locations, transitioning failover rating, evaluating, 251 to SIP trunks, 39-40 fault tolerance healthcare, UC implementations, best practices, 261 303-304 SRST, 93 high availability, 130 fax, 155-156