> From: Samir Srivastava [[email protected]] > > Hi, IMHO presentation of information in tabulated form helps a lot to > starters. Like ABNF it helps parser developers (expert of syntax & > semantic analysis) to develop it without referring each line of SIP > rfc's.
The tables are a useful guide to starters. But as others have noted, it is very difficult to keep the tables up to date, and there is no format for the tables that correctly presents the conditions for all "optional" headers. Parser developers may be tempted to use the tables to determine whether a message has all the required headers, but it is nearly impossible to make that determination other than while carrying out the processing for the message. The real rule for the presence of headers is: "Perform the processing that is mandated by the SIP message. Headers whose values are required to perform this processing must be present; headers whose values are not used in the processing are ignored. If a needed header is not present, the processing of the message is aborted and it has no effect. If the message is a request, an appropriate error response is sent (if enough information is present in the request to allow doing so)." Dale _______________________________________________ Sip mailing list https://www.ietf.org/mailman/listinfo/sip This list is essentially closed and only used for finishing old business. Use [email protected] for questions on how to develop a SIP implementation. Use [email protected] for new developments on the application of sip. Use [email protected] for issues related to maintenance of the core SIP specifications.
