SIP URI stands for “Session Initiation Protocol Universal Resource Identifier.” This is not to be confused with the related terms “Internet Protocol (IP)” or Universal Resources Locator (URL).

A SIP URI is the SIP addressing schema, or identifying string of characters, to call another person via SIP. It is, essentially, a user’s sip “phone number,” and it is in a format similar to email. The format is “sip:user @ host,  or sometimes “sip:user @ host.port.”

Some examples of SIP URIs are:

sip:clarkkent @
sip:Sue @
sip:mario @

As you can imagine, using numbers to dial SIP addresses is completely impractical, and this is by design. The purpose of SIP calling is to bypass the PSTN entirely and use only internet protocol. In order to assign a SIP URL to your phone, you must subscribe to a service that links (registers) your IP phone to your SIP address. Many VoIP providers do this, which is also called giving your “SIP Credentials,” but some VoIP providers prefer to withhold that information, either for security purposes, or because it works against their business model. Another method is to have the URL of your web site be linked to the SIP address.

In order to use a SIP phone to dial a SIP address, you must program the SIP address using the user portal. Once you have done that, you can use your phone address book to “dial” the SIP address. Two easy ways to do this are to use the outbound “click2call” command on your computer, which will ring your phone and the receiving phone, or to program the number into your VoIP phone’s speed dial/super dial, so all you have to do is press one or two digits to call the SIP address.

Additional Reading
What is a SIP Client?
What is URI?