I have downloaded Unitiy SIP .NET SDK and compared it with another SDK called Ozeki VoIP SIP SDK (voip-sip-sdk.com). The usage and functionalities were quite similar. Both of them can be easily used, online documentation is available, have free trials, they are .NET solutions. However I found that in Unitiy SIP .NET SDK there a few extensions which are not implemented. To sum it up I would prefer the Ozeki SDK because I could easily implement it into my application.
