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For reference, the following definitions are provided:
Country Code - The national prefix to be used when dialing TO a particular country FROM another country. The US country code is 1.
International Direct Dialing (IDD) prefix - The international prefix for dialing a call FROM the country listed TO another country. For typical PSTN calls, this is followed by the country code for the country being called. Some countries have multiple IDDs, and each is used by a different long-distance carrier.
National Direct Dialing (NDD) prefix - The access code used to make a call WITHIN that country from one city to another (when calling another city in the same vicinity, this may not be necessary). An NDD is followed by the city/area code for the place being called. When dialing from outside the country, the NDD is not used after dialing the country code. When dialing from within that country, the NDD is used, but the country code is not.
Note
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The calling party name service provided by some PSTN service providers requires that the telephone number in the To header (of the customer’s SIP Invite to
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46 Labs) be formatted as an e.164 number.
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Recommendations
46Labs 46 Labs recommends using 8 and 81 as the trunk access codes for local and long-distance calls.
When the trunk access code is set to 9 or 91, many customers have had issues with by mistakenly dialing 911 and then immediately hanging up after realizing their mistake. The 46Labs 46 Labs Peeredge Switches Switch can complete a 911 call in a fraction of a second (much faster than a user can hang up the call). This forces the PSAP to attempt a callback to the number dialed or to dispatch local law enforcement to the registered location of the calling party number if the callback failedfails.
46Labs 46 Labs recommends using e.164 dialing patterns.
Note: If an e.164 dial pattern is used, then all numbers in all relevant SIP headers (RURI, From, To, PAI, Contact, Diversion, etc.) in all inbound and outbound calls should be properly formatted as e.164 numbers.