Hi Matthew, Even if you find a mechanism in SIP of forcing an entire call to use the same transport type, it will cause problem when you are using DNS NAPTR records for SIP. When you do not know the transport of the server, then you use NAPTR queries to resolve the transport of the server. We need to query this before sending each request because there might be possiblity that TTL of the DNS record is small, so there might be a case when one request in a call is using TCP & other is using UDP. So please take care of these scenarios also when designing your solution.
Regards, Pravesh -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Matthew Gardiner Sent: Tuesday, November 08, 2005 2:24 PM To: [email protected] Cc: Mike Fielding Subject: [Sip-implementors] Is transport type a transaction or call specificproperty? Hi, I have some questions regarding the usage of TCP as the transport mechanism for SIP and would be grateful for any views people may have: Is the transport type used for one transaction in a call to be the same in other transactions of the same call? The RFC3261 section 18.1.1 seems to suggest that the decision regarding transport type should be made at the time of sending a request, i.e. if the request is larger than a certain size then use TCP, such a (large) request could obviously occur in a reinvite after the call was setup using UDP. Alan Johnston's "SIP: Understanding the session initiation protocol" further suggests that each TCP connection should be successively closed/re-opened per transaction. As my area of work is telephony, the idea of opening/closing connections throughout the life of a call seems a little sub optimal given the time taken making a socket API connect call. Do any others agree? Presuming that my understanding of the RFC3261 and A. Johnston's book to be correct (transport type is a per transaction property), is there any mechanism in SIP of forcing an entire call to use the same transport type for all it's transactions. thanks for your time, Matt _______________________________________________ Sip-implementors mailing list [email protected] http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors __________________________________ Yahoo! FareChase: Search multiple travel sites in one click. http://farechase.yahoo.com _______________________________________________ Sip-implementors mailing list [email protected] http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
