SIP phones or any SIP device with the ability to register, are essential in most FreeSWITCH installations for allowing users to communicate with each other. A registration is when a phone or other device informs FreeSWITCH that it is active and provides information (such as an IP address and port) on how to reach the phone across the network or Internet. FreeSWITCH stores this information for use later if someone wishes to contact the phone.
In this recipe, you will be registering a phone to FreeSWITCH. You will need to enter your credentials into your phone as well as into FreeSWITCH itself (both sides must match). We will cover only the FreeSWITCH server portion of registration in this book.