What is a SIP-URI?
A SIP URI is the SIP addressing schema to call another person via SIP. In other words, a SIP URI
is a user’s SIP phone number. The SIP URI resembles an e-mail address and is written in the
following format:
sip:user@host
SIP-URIs are defined in RFC-3261.
Why Should Anyone Care?
There's a quiet revolution underway as the old 4 kHz narrowband phone system is being
disrupted by a combination of cell phones and Internet phones with better features and
wideband audio (HD). Any phone call that passes through the PSTN (Public Switched Telephone
Network) is reduced to narrowband audio and incurs a toll. As a result, there is growing interest
in dialing SIP calls directly from one SIP Internet phone to another, bypassing the PSTN
completely. SIP-URIs provide an industry standard way of doing this.
Dialing SIP-URIs
The telephone keypad on most phones is not optimized for entering SIP-URIs, so this is an ideal
application for Phone Amego. Phone Amego allows SIP-URIs to be entered anywhere a phone
number is normally used, and will pass the SIP-URI unmodified to the telephone device or
service selected. A growing number of IP phones (i.e. Polycom and Yealink) and VoIP services (ie
CallCentric) can handle these correctly.
Phone Amego also handles URLs of the form <sip:xxx> allowing you to click on these links
wherever they appear.
Where to Store SIP-URIs
Since SIP-URIs are similar to Email addresses, they cannot be stored properly in the phone
number field of a person record in your Address Book. Apple's Address Book has a URL field type
which is perfect for holding a SIP-URI. What I've done is create a custom field in my Address
Book of type URL with the label "sip" to hold SIP-URIs. Clicking to open this URL will place the
corresponding call with Phone Amego.
Over time I'll be adding more integrated support for SIP-URI handling between Apple's Address
Book and Phone Amego. Searching for a matching contact in your Address Book should include
any SIP-URIs.
Selecting Default Applications
Phone Amego registers to handle URLs of the form <sip:xxx>, but other applications may
register for these as well in which case Launch Services will decide which application to invoke.
You can select which application you want to launch by default for various URLs by installing a
3rd party preference pane called "Default Apps". See <http://www.macupdate.com/app/mac/
Q: What's a URI?
A: URI stands for Uniform Resource Identifier. It is similar to a URL (Uniform Resource Locator)
but identifies a network resource like a phone rather than the location of a mailbox or document.
Q: How do I assign a SIP-URI to my IP phone?
A: You need to use a service that provides SIP name registration. VoIP service provider
CallCentric does this, and has peering agreements to allow free SIP-URI calls to most major
providers. Other providers like OnSip can also provide SIP-URI registration. If you have your own
registered domain name, your Email address can be your SIP-URI.
Q: Can I call Google Voice using a SIP-URI?
A: Maybe. Many users report this works if your VoIP provider has a peering agreement with
Google. The format of the SIP-URI is:
sip:+1NPANxxxxxxxxx@sip.voice.google.com
This works for me using CallCentric.
Q: Can Google Voice forward my calls to a SIP-URI?
A: Not directly at this time.