Differences between update and re-invite methods in SIP

 

In sip, both re-invite and update are used to modify the session parameter. The difference is that update does not affect the status of the dialog, and re-invite changes the status of the dialog. Therefore, update can be sent before the first invite is responded (that is, before 200ok of invite is received ). That is to say, update can be used to control early media. The re-invite can only be sent after the first invite cup responds (that is, after the call is established ).

Generally, you can use update and re-invite to change the session parameters after the call is established. But re-invite is used. Because update must be responded immediately. In this way, if you need to participate in the modification of the session parameter, it is not appropriate to use update. Most of the time, when the call is established and the session parameter is modified, user participation is required. For example, if you click an agree dialog box, re-invite is more common.