While it's easy to say this is preferred, it's not the right fit for most cases where an ordinary human is dialing the call. By including the Plus before the number, all parties involve understand that the next digits will be the country code, followed by the national and local number. Preferred: I recommend this format whenever possible, because it's the only one with a token that signals the type of number it is: the leading Plus. In the North American Numbering Plan (US, Canada, Caribbean), INVITE SIP/2.0 This model places the call with a leading country code. The UAS for '' has to know what 2207 means in that context. The extension 2207 probably only makes sense in the group owned by 'u2292442099'. You can expect to only see this when the INVITE Request URI represents digits that a user is dialing personally. An extension is a locally-defined telephone number, but which is not useable routing between carriers. In PBX-like environments, 'extensions' can be dialed. This is a very awkward format to support between carriers or systems, and quite impractical if multiple local areas are involved. For example, if this call is dialed by user 'u2292442099', and their US area code is '229', then the UAS may reasonably interpret the dialed digits 3160013 as +1-22 by prepending the national and area code to the dialed digits. One popular method is to apply the local area code of the calling party. When a human is dialing the number to place a call across the PSTN, the receiving system (INVITE User Agent Server, UAS) will need to determine the intended PSTN telephone number. Within the UK, you might call a London number by dialing eight digits: INVITE SIP/2.0 When the SIP invite represents the digits a user actually dialed on his keypad, the local number will be most common. For example, in the United States, you might see this complete national number: 9193160013. Perhaps the most common format is the complete national number. If you can find a way to interop end-to-end between the two call-control servers, without having to rewrite the number in an Session Border Controller in the middle, then you prevent substantial hassle. will have certain capabilities and defaults. The software you're using - BroadWorks, Metaswitch, Asterisk, Sonus, Genband, etc. This article is intended to familiarize you with many of the common options.

There are several popular formats, and they occur in the Request-URI (after the 'INVITE') and in the To header. One of the most common questions for SIP interop is how the called telephone number will be formatted. Determine what control codes are supported, such as *67 Determine which short codes are supported, such as emergency codes 911, 111, and 0ĥ. Establish format for international telephone numbers.Ĥ. Establish format for national telephone numbers.Į.164 With Plus is recommended, e.g., +12292442099ģ.

Establish format for local telephone numbers.Ģ. If you're not, you may have a lot to fix.ġ. If you're lucky, the two systems have a lot in common. When setup two SIP systems to exchange phone calls, you need to be aware of the issues. One system expects national telephone numbers, and another system expects international-formatted numbers. Then there's the codec used for audio: One system uses G.722 and another uses G.722.2. For example, identifying the calling party varies between platforms: One system uses P-Asserted-Identity to indicate the caller, and another uses From. When we teach classes on VoIP networks, we discuss the variety of SIP standards that can be used by working systems.

Sip phone number