Telecom Informer

    

by The Prophet

Hello, and greetings from the Central Office!

I'm winging my way across the Sea of Japan on my way back to Seattle.  Construction of the new Beijing Central Office is nearly complete, and it's time for a trip to headquarters to discuss the details of our operation plan.  There is still plenty of work to do in Beijing, and I will continue to be based there for some time.

Local Number Portability (LNP) is part of our operation plan.

We're building the new Central Office to be ready to implement it.  Even though there is no local number portability available in China yet, we expect it to happen eventually.  Unlike in the U.S., there aren't a bevy of options in China for your home phone; there is only fixed line service from China Telecom or China Unicom, depending on what part of the country you are in.  If you move, your phone number will change, and you don't even have a choice of long distance provider (although there are dozens of dial-around services providing competitive long distance rates).

You do have a choice between three mobile telephone providers (China Unicom, China Mobile, or China Telecom), but you're unable to take your number with you if you switch carriers.  And there is certainly no concept of wireline to wireless portability.  Skype is popular (but illegal in China), and VoIP services have not caught on the way they have in North America.

What a contrast to the United States!

Since 1997, when LNP was first introduced, you've had a choice of multiple local phone companies.  While there are typically not more than three broadband choices (typically one cable provider, one traditional local phone company, and a wireless service provider) in major American cities, you have plenty of choices for home telephone service.

Traditional phone lines, known as POTS, are a rapidly diminishing share of the market, although this is a competitive market with numerous companies who can sell you a local dial tone (although this is often actually provided by your local phone company under a reseller arrangement).  VoIP service from the local cable provider has half (or more) of the residential fixed line market in some cities.

Meanwhile, there are four major nationwide wireless mobile phone companies (and a couple of dozen smaller local and regional providers) with a seemingly infinite number of resellers and Mobile Virtual Network Operators (such as TracFone, Boost Mobile, and Straight Talk).

Americans take for granted the ability to keep their phone number when they switch from a fixed line to wireless phone, or move from one wireless provider to another.  And the system more or less works quickly and seamlessly today.

The central nexus of the number portability system is the Number Portability Administration Center, or NPAC.

Run by Neustar, the FCC-appointed administrator of the North American Numbering Plan (NANP), NPAC is a carrier-neutral one-stop shop for number portability.  Neustar isn't a phone company, isn't owned by any phone companies, and doesn't have an ownership stake in any phone companies, but makes most of its money from phone companies (it also administers the .us top-level domain and runs an Internet DNS root server among other critical infrastructure roles).

Prior to local number portability, telephone companies almost exclusively used a Telcordia publication called the Local Exchange Routing Guide (LERG) to determine how to route calls.  Based on the NPA-NXX of a called number, the long distance carrier looks up the Common Language Location Identifier (CLLI) for the switch serving the number you call and the tandem serving that switch.

This is used to route your call.

For example, if you make a call to (206)-386-4656, the carrier would first reference the LERG, which would then deliver the CLLI of the tandem (STTLWA06C9T) and the end office (STTLWA06DS6).

The long distance carrier would select a route to deliver the call, drop it off with the appropriate routing data at the tandem, and the local exchange carrier (Qwest in this case) would route the call to the end office.

Now suppose the Seattle Public Library (used in the above example) changes their local service provider to Level 3, a local CLEC.  This creates a couple of problems.

First of all, the CLLI of the end office is now STTNWAHODS0, and the tandem has changed too.  It's now EVRTWAXA03T, a Verizon (ex-GTE) tandem, which isn't even in Seattle.

A Local Routing Number (LRN) has also been assigned.  Although the telephone number remains (206)-386-4656, the LRN is now in the (206)-569 NPA-NXX.

The OCN (Operating Carrier [Company] Number) has also changed, which creates another problem; access charges are paid to the carrier that delivers the call, and when a number is ported it's necessary to track this accurately.  In the VoIP wholesale world, which is how long distance calls are increasingly handled, routes are selected based on the serving OCN.

All of this means we now need more data to route the call.

If we only use the information the LERG gives us, we're going to deliver the call to the wrong switch, through a tandem in the wrong city, with the incorrect LRN.  The call will still go through (because even though Qwest is not required by FCC rules to forward incorrectly routed calls to ported numbers, they generally provide this service), but Qwest doesn't do anything for free and the Revenue Assurance department is rarely amused by expensive transgressions in translations.

How, then, do we complete the call?  Enter NPAC.

Along with providing number portability services to both wireless and wireline carriers, Neustar operates the NPAC database.  For every telephone number in the North American Numbering Plan, the NPAC database maintains the associated LRN.  This can be used to determine a telephone number's true CLLI and end office, and also the correct OCN for routing and billing.

A database "dip" is generally performed on the switch using the Intelligent Network (IN) or Advanced Intelligent Network SS7 triggers.  Of course, Neustar doesn't supply this information for free.  In addition to charging a monthly subscription fee for access to the database, they charge a few ten-thousandths of a cent per dip.

This can really add up over millions of telephone calls a day.  Predictably, our Revenue Assurance department doesn't like that either, so we take measures to minimize these costs, which are called "dip fees."

After all, it's not only long distance carriers that get slammed with NPAC dip fees.  Local carriers have to pay too, because locally dialed phone numbers (especially wireless phone numbers) may have been ported.  To avoid unnecessary charges, we don't perform dips on our own subscribers' numbers and we cache dips for frequently dialed numbers for a few hours (after all, there is no need to dip 300 times a minute to find out whether the local Top 40 station's phone number has ported in the middle of an on-air promotion).

And with that, it's time for me to settle in for the long flight ahead.  Enjoy your spring, and don't call anywhere I wouldn't!

Shout outs to:

References
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