, 117 status codes, 117-118 status line, 133 S/MIME confidentiality, 189 successful final, 148 SAP (Session Announcement Protocol) RESV messages, RSVP, 78 announcements, 81 RFCs (Request For Comments), 46, 227 session descriptions, 82 BCPs (Best Current Practices), 50 scalability SIP information, 221 IETF protocol design, 44 standards track, 50 SIP, 110 roaming user sessions, 3G mobile Schulzrinne, Henning, Web site, SIP systems, 197 information, 223 robustness, IETF protocol design, 44 SCIP (Simple Conference Invitation route headers, SIP requests, 139-140 Protocol), 92 routers, 31 SCPs (Service Control Point), 25 routing SDP (Session Description Protocol), 82, 91 datagrams, 32 attributes, 85 load balancing, 32 session descriptions, 83 multicast, 62 syntax, 83-84 advantages, 64 Index SDPng (SDP Next Generation), 87, 108 SIP (Session Initiation Protocol), 30 security ACK requests, 121-122 S/MIME confidentiality, 189 application decomposition, 114 SIP, 187 authentication, 187-189 sending commands, SIP extensions, 186 bridging, 210 servers building applications, 192 presence, 200 BYE requests, 125 SIP, 116 call stateful proxy servers, 127 forking proxy, 104 CANCEL requests, 123-124 group addresses, 104 CANCEL transactions, 148 location, 105 clients, 116 proxy, 103 conferencing, 214 redirect, 102, 105 CSCFs (Call/Session Control services, Internet, 59-61 Functions), 194 session descriptions decentralized multipoint conferences, 217 SAP, 82 end-system intelligence, 109 SDP, 83-85 entities, 98 SIP, 95, 108 extensions, 165 sessions asynchronous event notification, 179 distribution, 95 automatic UA configuration, 172-173 establishment, 94, 108 caller preferences, 177-179 SIP extensions COMETs, 174-176 transfers, 184 design guidelines, 163 type independence, 164 event notification framework, 179-180 signal attenuation, 14 instant messaging, 171, 200 signal spectrum, 12 method semantics, 164 signalling mid-session transactions, 169 control plane, 8 multiple message bodies, 170 digital. See digital signalling. negotiation,