The Telcordia LERG Routing Guide is a comprehensive data product produced monthly by the Telcordia Routing Administration (TRA). It is primarily used by telecommunications service providers operating within the North American Numbering Plan (NANP), which is World Zone 1. Its data supports the current local exchange network within the NANP and identifies reported planned changes in the network. The acronym "LERG" originally stood for Local Exchange Routing Guide, and is a trademarked term of Telcordia Technologies, Inc., now a division of Ericsson.
The LERG Routing Guide provides data to support:
Routing of calls by service providers in the public switched telephone network (PSTN) and interconnection points of the PSTN with Internet Protocol (IP) networks.
A wide range of business needs of companies that require information about the network, numbering, and other data
The LERG Routing Guide includes:
Operating Company Numbers (OCN), company names, routing contacts
Country Code assignments
Numbering Plan Area (NPA) Assignments (also known as area codes)
Local access and transport area (LATA) codes
Destination Code assignments (NPA NXX thousands-blocks)
Access Tandem codes
Oddball NXXs (e.g. 911, 976)
Switching Entity Record detail (e.g. Equipment Type, V&H Coordinates), including PSTN and IP network elements
Rate Center details (e.g. V&H Coordinates) and Localities (includes County and Postal Codes (US) of Localities)
Switch Homing Arrangements (tandem and other switch-to-switch interconnections)
Operator Access Tandem Codes (ATCs)
Location Routing Numbers (LRNs)
