SIP Flavors

One of the biggest hurdles faced when deploying SIP systems is the fact that every implementer has a different interpretation of the SIP specifications. The second is that there are so many options one might implement. There are lots of optional extensions available for SIP and not every implementers implements every options, nor is there a generally-agreed subset.

Well, that is not entirely correct. Various organizations, like the SIP Forum, have tried to address this problem by essentially defining a "profile" of SIP that specifies the various features that must be implemented. However, the problem still exists, because different organizations define different profiles with different feature sets!

So, there are various interpretations of SIP and various standards bodies and "want to be" standards bodies producing conflicting profiles of SIP that leads to a never-ending problem for those who want to deploy SIP in practice.