ields, 91 defined, 71 OK response, 90 INFO, 93-94 sent within dialog, 89-90 INVITE, 72-74 OPTIONS method, 81-82 MESSAGE, 90-93 defined, 81 names, 71 example, 81-82 NOTIFY, 89-90 mandatory headers, 76 OPTIONS, 81-82 message body, 81 PRACK, 94-96 See also Methods REFER, 82-86 Organization header field, 134 REGISTER, 74-76 overlap dialing, 121 SUBSCRIBE, 86-89 unknown, 71 parallel search example, 225-30 UPDATE, 96-98 defined, 225 midcall mobility, 197-99 illustrated, 226 with INVITE and Replaces, 199 See also Call flow with re-INVITE, 197 P-Asserted-Identity header field, MIME-Version header field, 160 Min-Expires header field, 154 Path header field, 203 Index personal mobility, 194-95 calls with, 25-30 defined, 194 defined, 47-48 support, 195 forking, 52 See also Mobility search service, 50 P-headers, 203-4 stateful, 49, 50 physical layer, 4 stateless, 49 Point-to-Point Protocol (PPP), 4 UAs vs., 48 P-OSP-Auth-Token header field, See also Servers 145-46 PSTN and Internet Interworking (PINT) P-Preferred-Identity header field, protocol, 88 Public Switched Telephone Network PRACK method, 94-96 (PSTN), 46 defined, 94 gateways, 47 example, 95-96 interworking, 111 mandatory header fields, 96 overlap dialing, 121 message body, 95 protocols, 176-77 reliable responses, 95 UAC generation, 94 RACK header field, 152-53 See also Methods Real-Time Transport Protocol (RTP), 8, 171-74 precall mobility, 196 audio video profiles, 174-75 presence call flow example, 256-59 Control Protocol (RTCP), 173 Events extensions and, 33 development, 171 example, 33-38 lost packet detection, 172-73 information, 33 octets, 171-72 packages, 38 packet header, 172 protocol, 33 packet types, 173 servers, 45 sessions, 174 URLs, 101 Reason header field, 147-48 work, 264 Record-Route header field, 134-35 presence agents (PAs), 44-45 redirection responses, 112-13 authentication, 45 redirect servers, 52-55 defined, 44 defined, 52-53 information collection, 44 example, 53 Priority header field, 144-45 redirection response, 53-54 See also Servers Privacy he