CLLI code

CLLI code (COMMON LANGUAGE Location Identifier Code and pronounced silly) is an identifier used within the North American telecommunications industry to specify the location and type of a piece of telecommunications equipment or of a relevant location such as an international border or manhole location. Originally, they were used by Bell Telephone companies, but since all other telecommunications carriers needed to interconnect with the dominant Bell companies, CLLI code adoption eventually became universal. CLLI codes are now maintained and issued by Telcordia, which claims trademarks on the names "Common Language" and "CLLI".

CLLI codes are useful to telephone companies for ordering phone service, for rating of call detail records (and hence billing), and to assist in tracing calls. CLLI codes are associated with Vertical and Horizontal coordinates (frequently abbreviated to "V and H coordinates"), which were developed by AT&T researcher Jay K. Donald to provide a relatively simple method of calculating distance between two network locations. Various mileage-sensitive services are priced according to the V and H coordinates associated with the two endpoints' CLLI codes.

There are three formats for CLLI codes, but the most commonly used is the Network Entity format, an eleven-character format used to describe the location of network equipment. A CLLI code is composed of four sub-fields:
 * Four characters to denote the city (formally called the Geographical code),
 * Two characters to denote the state or province (the Geopolitical code),
 * Two characters to denote the specific location or building address (the Network-Site code), and
 * Three characters to specify a particular piece of equipment (the Network Entity code).

Each of the fields is defined fairly precisely, but there is room for interpretation and there are therefore some possibilities for confusion as shown in the examples below:

Examples
HSTNTXMOCG0
 * HSTN = Houston
 * TX = Texas
 * MO = The AT&T telephone exchange office at 4068 Bellaire Boulevard in West University Place, Texas -- the office is known as the "Mohawk office"
 * CG0 = The first (or perhaps only) analog telephone switch at that location

This code shows two characteristics:
 * Telephone companies often give names to their central offices. The names frequently relate to the name given to the exchanges served from that office in the days of two-letter, five-number dialing, where a telephone number might have been referred to as "MOhawk 3-1234".  See telephone exchange names for more information.
 * The Geographical code field does not always align exactly with the city location. West University Place is an enclave of Houston, Texas.

PTLDOR12DS0
 * PTLD = Portland
 * OR = Oregon
 * 12 = The Qwest "Atlantic office" at 2911 NE 24th Ave
 * DS0 = The first (and perhaps only) digital telephone switch at that location

Some telephone companies named their central offices, but did not reflect this name in the CLLI code, as in the above example with a numeric location code.

PTLEORTEDS0
 * PTLE = Portland
 * OR = Oregon
 * TE = A specific address: 6038 NE 78th Court
 * DS0 = The first (and perhaps only) digital telephone switch at that location

The item to note in the above example is that Portland is usually abbreviated as "PTLD", but because of the relatively small number of possible combinations available in the two-character location code, the city abbreviation must occasionally be modified for locations added later, usually by incrementing the fourth character in the code.

DLLSTXRNDS1
 * DLLS = Dallas
 * TX = Texas
 * RN = The Richardson office
 * DS1 = The second digital telephone switch at that location

Note that this location is actually in Richardson, Texas, not Dallas. Apparently, the organizational structure of Southwestern Bell Telephone at the time considered Richardson to be within its own Dallas organization, although the cities themselves have always been legally separate.