1 performance/sizing, 178-180 operations and management security, 173-175 issues, 176-178 session management, 162-168 performance/sizing issues, support, 182-183 178-180 system specification, 178 security issues, 173-175 SIP trunking models scalability, 130 show commands, 240-241 SIP trunk capacity engineering, 137 signaling encryption, 124 security considerations signaling methods, call centers, 28 ACLs, 114 signaling protocols, comparing, 4-5 authentication, 122-123 SIP header manipulation, configuring, best practices, 261 238-239 costs, 53-54 SIP normalization, 121, 145-148 firewalls, 116-119 SIP protocol attacks, protecting hostname validation, 115 against, 120-122 SIP registration, configuring, 239 implications, evaluating, 248 levels of exposure, 113-114 SIP trunking models centralized, 84-85 media encryption, 124 call patterns, 94-95 registration, 122-123 cost, 92 SBC vendor technical requirements, 173-175 DID number portability, 88-89 signaling encryption, 124 emergency call routing, 93-94 SIP protocol attacks, protecting geographic boundaries, 89 against, 120-122 high availability, 93 toll fraud, 123-124 operational implications, 92 topology hiding, 116 oversubscription, containing, 90 selecting QoS considerations, 91 protocols, best practices, 258-259 regulatory considerations, 90 SIP provider direct media model, 96-97 best practices, 256 distributed, 85-86 bidder background, 186-188 call patterns, 94-95 bidder references, 188 cost, 92 cost-related issues, 188-189 DID number portability, 88-89 SIP trunking model, 83-84 emergency call routing, 93-94 servers, billing servers geographic boundaries, 89 post-paid billing servers, 61 high availability, 93 real-time billing servers, 61 IP addressing, 95 SIP trunking in SP networks, 61-62 operational implications, 92 service provider load balancing, 134 oversubscription, containing, 90 session management, SBC vendor QoS considerations, 91 technical requirements, 162-168 regulatory considerations, 90 sharing presence information as SIP hybrid, 86-87 trunking fea