E.164 « Class in Session: Cisco

Posts Tagged 'E.164'

Communications Manager: To Globalize or Not?

A new feature arrived with CUCM 7.x and higher and that is the new ability to use the new globalized e.164 feature. This feature is simply adding a + followed by the 1 to 3 digit country code, then the National Dialing code, and finally by the subscriber code.

The + actually means the country’s access code that I happen to be traveling in. So in Europe, most likely the international access code would be ’00′. However, on my cell phone I would dial +14089347568 then the cell phone carrier would strip the + and replace it with 00. Therefore as an end user, no matter what country I am dialing from, I never have to know that country’s international access code to call home.

Now, this same idea has caught on in PBX systems to provide globalized call routing. The overall goal with globalized call routing is that an end user or carrier would normally enter or transmit the digits to the PBX or CUCM using a local format like 10 digits in North America. The number would then be converted into a global format and routed accordingly.

If the call was going off net, the user would dial a 7 or 10 digit number, which would be converted into the global format. Then a route would be matched and before sending a call setup back to the carrier, the number would be converted back to the local format needed by that local carrier.

Seems a little busy, but if you have a worldwide business with remote offices in Europe, Asia, and South America, using the globalized call routing method will significantly reduce the complexity of your overall dial plan – especially when you are trying to incorporate Toll Bypass and/or Tail End Hopoff procedures.

Another reason that you may want to move to this global format for internal routing is the fact you may be integrating with Microsoft OCS 2007 installations. Microsoft OCS 2007 defaults to global routing using the global e.164 standard, and in order to accept this number type and route it effectively, it would make more sense to go ahead and adopt this standard within your CUCM installation as well.

For more information on setting up globalization in CUCM, I recommend the Global Knowledge CMDPI – Cisco and Microsoft Dial Plan Integration course.

Author: Joe Parlas

ENUM for the Enterprise

Published July 17, 2009 Joe Parlas , Unified Communications Leave a Comment
Tags: dialing, E.164, ENUM, standards

In my last post we looked closely at E.164 and the IETF, and how they made subtle changes to the existing E.164 numbering plan. In essence, all devices with a phone number would reflect the entire number with a plus symbol tagged onto the front of the number, like +14043567893 if you’re in North America. When sent to the provider, the plus symbol (if the provider supports this numbering plan) would tell them that this was an international call and to replace the “+” with that country’s number routine to request international service.

The question is, is this being adopted in the enterprise and if so, how would that make an IP PBX or PBX administrator’s life easier? Continue reading ‘ENUM for the Enterprise’

E.164 – The modern dial plan

Published July 2, 2009 Joe Parlas , Unified Communications Leave a Comment
Tags: dialing, E.164, standards

When we are addressing Voice over IP we need to remember that essentially we would like to reach customers over the PSTN or SS7 network. The only avenue to date to do this, is by using something called the telephone number. However, that number has undergone some changes recently.

The International Telecommunication Union (ITU) is the responsible body for all telephony numbering around the world. The way the numbering plan laid out is:

A telephone number can have a maximum of 15 digits
The first part of the telephone number is the country code (one to three digits)
The second part is the national destination code (NDC)
The last part is the subscriber number (SN)
The NDC and SN together are collectively called the national (significant) number

Now, each geographic area has responsibility for it’s own numbering plan. The United States and Canada share equally in the North America Numbering Plan (NANP) which entails a single-digit country code, followed by a 3-digit area code, a 3-digit prefix, and a 4-digit subscriber code. In other words, our numbering system is quite fixed. Other countries have variable length numbering plans, like England where the number grows based upon the density of a given city.

The E.164 has developed into something broader called ENUM (TElephone NUmber Mapping) which was the brain child of the IETF (internet engineering task force). Using the international E.164 number as a model, ENUM will assign a specific Uniform Resource Identifier (URI) to each and every networked device — including analog telephones and fax machines, smart phones, or computers. The reason for this is to make it easier to look up the numbers or devices using DNS servers on the internet.

The URI could be in a format of an email address (joe.parlas@cisco.com) or a number with an assigned domain name (+6197256999@cisco.com). With URI all these devices will be able to contact each other directly using a single network address or phone number. ENUM also deals with storage of these numbers on the DNS (domain name server) so that voice over IP phones could look up a number over the internet and be connected to another voice over IP system.

RFC 3761 is defines the format of the number as:

The Application Unique String is a fully qualified E.164 number minus any non-digit characters except for the “+” character which appears at the beginning of the number. The “+” is kept to provide a well understood anchor for the AUS in order to distinguish it from other telephone numbers that are not part of the E.164 namespace.

For example, the E.164 number could start out as “+44-116-496-0348″. To ensure that no syntactic sugar is allowed into the AUS, all nondigits except for “+” are removed, yielding “+441164960348″.

So the full ENUM number must begin with a leading “+”. But the question remains, what does the “+” represent? Basically it represents your country’s access code to dial out to make international calls. For instance, if I were to dial an international number from my home in North America, I would begin by dialing “011” which is our code fore requesting international service.

In essence, a fully qualified ENUM number is one that could be dialed by any device, any place in the world, and the call would be properly set up. If you look closely at your cell phone when you dial from outside your home country you will notice that the cell provider has translated the number into a fully-qualified ENUM during the calling operation.

The beauty in this system is that I don’t have to worry about remembering international access codes for different countries, as long as the provider understands the leading “+” symbol.

Author: Joe Parlas