[ removed [EMAIL PROTECTED] from the cc list, cdotb newsgroup removed ] Prakash:
Here is my POV on this Prakash R wrote:
1) Assuming we have an application built using SIP stack developed to comply with RFC 3261, does it have to interwork with RFC 2543 compliant stack? If not RFC2543, then what about the various drafts (draft 5, draft 6, ..., draft 9)?Not necessarily. There is nothing that requires backward compatibility. However, if I were selling equipment / stacks, I would be concerned about it.
2) I was also wondering about the theoretical possibility of backward compatibility? Any provisions in the protocol for an implementation to detect and manage this issue?
Yes. One dead giveaway :-) is the branch magic cookie prefix.. The branch parameter for a request has a specific prefix indicating it is 3261 or at least some high 2543 bis revision compatible.
3) Is it feasible for applications to have dual SIP Stacks? (Both 2543 and 3261)?
Yes. Backward compatiblity is quite tricky but do-able. There are many gotchas in the parsing of headers, route management, transaction matching and required headers to name a few. ( RFC 3261 has a list of differences between 3261 and 2543. ) However, if you are willing to live with some restrictions (for example, if you want to restrict yourself only to user agent functionality) then the problems are fewer.
4) Does it make sense now to still deal with 2543?
Depends on what you want to do. If you want to sell stuff then yes. If you want to research or experiment then I would say not. Many implementations have self-updating features where they go off and update the stack by dynamically downloading code using udpate managers. Thus over time this will be less and less of a problem. I am guessing one year out we will see few signs of back level stacks but that is only a gut feel.
Thanks in advance. Regards,
--
M. Ranganathan
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