115-16 client error, 113-23 408 Request Timeout, 116 global error, 125-26 410 Gone, 116 informational, 108-11 411 Length Required, 116 redirection, 112-13 413 Request Entity Too server error, 123-25 Large, 117 success, 112 414 Request-URI Too Long, 117 Retry-After header field, 135, 136 415 Unsupported Media Type, RFC 2543, 267-68 RFC 3261, 268-69 416 Unsupported URI Scheme, round-trip time (RTT), 57 Route header field, 152 420 Bad Extension, 117 routing 421 Extension Required Internet packet, 12 117-18 triangular, 65, 194 422 Session Timer Interval unicast, 12 Too Small, 118 RSeq header field, 156-57 423 Interval Too Brief, 118 428 Use Authentication server error responses, 123-25 Token, 118 501 Not Implemented, 124 429 Provide Referror 502 Bad Gateway, 124 Identity, 118-19 503 Service Unavailable, 124 480 Temporarily 504 Gateway Timeout, 124 Unavailable, 119 505 Version Not Supported, SIP: Understanding the Session Initiation Protocol server error responses (continued) address names, 26 513 Message Too Large, 125 brief history, 3-4 defined, 123-24 calls with proxy server, 25-31 See also Response(s) defined, 1 Server header field, 155 Events extensions, 33 servers, 47-55 extended functions, 2 defined, 47 gateways, 45-47 proxy, 47-52 H.323 comparison, 187-91 redirect, 52-55 header fields, 127-60 registrar, 31-32 hearing impairment design team and, 262 registration, 55 Internet and, 1-14 Service-Route header field, 203 interoperability test events (SIPit), 3 Session Announcement Protocol (SAP), 163 introduction to, 17-42 Session Description Protocol (SDP), mobile operators and, 189 8, 163-71 mobility, 194-95 applications, 163-64 popularity, 3 attributes field, 168-69 presence and instant message example, attribute values, 170 33-38 bandwidth field, 167 as PSTN, 46 connection data field, 166-67 registration example, 31-33 development, 163 request messages, 71-104 email address field, 166 response code number, 21 encryption keys field, 167-68 response messages, 107-26 field list, 165 servers, 47-55 information, 164 