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Common Language Location Identification

Common Language Location Identification (CLLI) is a standardized alphanumeric coding system developed for the to uniquely identify physical network locations, such as central offices and cell sites, as well as associated equipment functionalities like switches and servers. CLLI codes consist of either 8 characters for denoting physical sites or 11 characters when specifying attributes, enabling precise geographic and operational referencing across global s. Administered by iconectiv as part of its TruOps Common Language services and maintained in the CLONES database under ANSI standards, CLLI originated from efforts to standardize location data in North American telecommunications, evolving from Bell System practices to support modern interconnection needs. The system comprises six core elements: geographical codes (e.g., four letters for city), geopolitical codes (e.g., two letters for state or province), network-site codes, network-entity codes, network support-site codes, and customer site codes, which together form one of four basic formats—network site, network entity, network support site, or customer site—to ensure unambiguous identification. In practice, CLLI codes are essential for automating processes like ordering, provisioning, billing, and interconnection between service providers, and they are mandatory for assigning (NPA/NXX) codes as well as preparing Access Service Requests (ASRs) and Local Service Requests (LSRs) per ATIS industry guidelines. By providing a consistent, machine-readable framework, CLLI reduces errors in network planning and build-out—potentially cutting redundant infrastructure by up to 20%—while supporting regulatory compliance, asset tracking, and efficient collaboration among over 1,800 communications service providers worldwide. Access to the full CLLI database requires licensing through , with tools like and services facilitating integration into operations.

Overview and Purpose

Definition and Scope

Common Language Location Identification (CLLI) is a standardized 11-character alphanumeric developed for the , with origins in North American networks, to uniquely identify physical locations, equipment, and functions within networks. This provides a precise, machine-readable identifier that encompasses geographic details, site specifics, and operational attributes, facilitating accurate tracking and reference in network operations. An 8-character variant exists for denoting locations without functional details, allowing flexibility in partial identifications. The scope of CLLI is strictly confined to telecommunications infrastructure, including network sites such as central offices and cell towers, support sites like poles and manholes, equipment such as switches and transmission gear, and . It excludes applications outside the sector, ensuring focused utility in operations, provisioning, billing, and processes. By standardizing these identifiers, CLLI promotes among over 1,800 communications service providers, enabling seamless data exchange and reducing errors in . A core feature of CLLI is its assignment of unique codes to millions of registered sites worldwide, stored in the centralized CLONES database, which supports automated workflows and global consistency despite its North American origins. CLLI was first introduced in the late 1960s as part of practices to standardize location referencing in an expanding network.

Administration and Governance

The administration and governance of Common Language Location Identification (CLLI) codes are handled by , the current steward of the Common Language Information Services, which maintains the centralized CLONES database for code assignment and management. holds the trademarks for CLLI and related Common Language products, ensuring their standardized use across the global . As the ANSI maintenance agent, oversees compliance with norms, including the ATIS-0300253 , and facilitates industry collaboration for ongoing relevance. New CLLI codes for sites or facilities are registered through 's processes, requiring submission of details via the LOA (Letter of Authorization) method for a one-time or an annual subscription license that includes usage charges for creation, amendment, deletion, and querying in CLONES. Upon approval, codes become globally unique identifiers, adhering to validation rules based on four formats (network site, network entity, network support site, and customer site) and six core elements such as geographic and functional specifications. Non-licensees can request codes online or through the Common Language Center, while licensees access CLONES directly for self-management. Governance emphasizes adherence to ANSI-accredited standards and ITU-related telecommunications protocols for , with conducting continual assessments and updates to the code system. The CLONES database contains millions of registered CLLI codes worldwide as of 2025, supporting precise network identification for over 1,800 communications providers.

Historical Development

Origins in the Bell System

The Common Language Location Identification (CLLI) system was developed in the late 1960s by Bell Laboratories as part of the broader Common Language Information Services initiative to standardize the identification of network sites within the rapidly expanding telephone infrastructure. During this period, the was experiencing significant growth, with millions of new telephone lines installed annually and the introduction of advanced switching technologies that necessitated more precise and uniform location tracking across operating companies and the Long Lines department. The primary motivation for CLLI's creation was to replace fragmented, ad-hoc location identifiers—such as informal names or local numbering schemes—that had proliferated in the monopoly-era , leading to inefficiencies in equipment inventory, maintenance, and interconnection planning. By establishing a structured coding system, aimed to facilitate seamless communication and data management among the system's far-flung facilities, including central offices, switches, and transmission points, thereby supporting the Bell System's goal of reliable nationwide service under a single administrative umbrella. This approach drew conceptual parallels to existing geographic coding standards but was specifically adapted for applications like wiring diagrams and switching hierarchies. CLLI was formalized in Bell System Practices (BSP) documentation in 1982, with the initial codes assigned to central offices to denote their precise geographic and functional attributes. These BSP sections, such as 795-100-100, provided detailed guidelines for code assignment and usage, ensuring consistency in engineering records and operational procedures throughout the pre-divestiture era. The system's implementation marked a key advancement in network administration, enabling automated data processing and reducing errors in the handling of the 's vast equipment inventory.

Evolution Post-AT&T Divestiture

Following the 1984 divestiture of , management of the Common Language system, including CLLI codes, transferred to Bell Communications Research, Inc. (Bellcore), a central services organization established to support the newly independent Regional Bell Operating Companies (RBOCs) in maintaining and standardization of network identification practices. Bellcore assumed responsibility for administering and updating the CLLI database, ensuring consistent use across the fragmented post-divestiture landscape while preserving the original design for location coding. In the , CLLI expanded to accommodate , incorporating identifiers for sites and initial locations as and packet-switched services proliferated. A key milestone was the 1996 ANSI T1.253 standard, which formalized CLLI specifications and aligned with the , facilitating broader industry adoption beyond the RBOCs by enabling competitive local exchange carriers to integrate standardized location codes for interconnection. The Act's deregulation of local markets accelerated this shift, promoting CLLI as a universal identifier for planning and routing among diverse providers. The 2000s saw Bellcore rebranded as Telcordia Technologies in 1999, reflecting its evolution into a broader consulting and standards body while continuing to oversee CLLI through systems like CLONES for code assignment and validation. Telcordia enhanced CLLI's utility by integrating it with (V&H) coordinates, a legacy refined for precise distance-based calculations in expanded networks. By the 2010s, amid rapid broadband proliferation, administration shifted to following Ericsson's acquisition of Telcordia and the 2013 rebranding, adapting CLLI to include non-traditional sites such as centers and supporting fiber-optic and infrastructure growth. This evolution emphasized CLLI's role in standardizing identifications for diverse assets, including towers and edge facilities, to streamline provisioning in competitive, multi-vendor environments.

Code Composition

Geographic Component

The geographic component of a Common Language Location Identification (CLLI) code comprises the first six characters, serving as a standardized identifier for the broader of a network site or facility. This prefix establishes the foundational geographic context, distinguishing locations at a level such as cities, towns, or metropolitan areas within specific jurisdictions. Developed under the oversight of organizations like Bell Laboratories and later managed by Telcordia (now ), the component ensures precise, unambiguous referencing in operations worldwide. The CLLI code format is defined by ANSI ATIS-0300253-2011. The structure begins with a four-character place code in positions 1 through 4, consisting of alphabetic characters that are left-justified and blank-filled if the name abbreviation is shorter than four letters; this code is derived directly from official geographic names for entities like cities, suburbs, villages, or even natural features such as mountains and bodies of water. For instance, "NYCM" denotes , while "DNVR" indicates . Following this, positions 5 and 6 hold a two-character geopolitical code representing the state, province, territory, or country, aligned with established standards such as the (USPS) abbreviations—for example, "NY" for or "CO" for . Together, these six characters form a globally , as the place code is distinct within each geopolitical unit, preventing overlaps even for similarly named locations in different regions. Assignment of these codes follows rigorous rules to maintain accuracy and uniqueness, administered through the Central Location Online Entry System (CLONES) database by iconectiv's Common Language program. Codes are based on verified official place names from governmental or authoritative sources, with new assignments requiring validation to avoid duplication; in cases of conflict, modifiers like county names may be incorporated into the place code (e.g., "JCCT" for Jacksonville in a specific county, Pennsylvania). For unincorporated areas or sites lacking formal boundaries, the code is assigned to the nearest recognized place name to ensure comprehensive coverage without gaps. This process, originally codified in Bell System practices, emphasizes global non-duplication of the full six-character sequence, supporting hierarchical location mapping from broad metro areas to precise urban centers. The design of the geographic component facilitates advanced applications by linking each code to coordinates within the CLONES/LocateIt , enabling geospatial analyses such as computations for network routing and optimization. This integration provides a for hierarchical , where the place code can represent aggregated areas (e.g., a metropolitan zone) or pinpoint specific municipalities, underpinning efficient management without delving into site-specific details.

Site and Building Component

The site and building component of a CLLI code identifies the specific physical site or building, such as a central office or remote terminal, within the geographic area defined by the preceding characters. In 11-character network entity codes and 8-character network site codes, this component occupies positions 7 and 8 and consists of two characters, either both numeric (00-99) or both alphabetic (AA-ZZ). This format ensures unique identification of structures like wire centers, headends, and other facilities in the same location. Both numeric (00-99) and alphabetic (AA-ZZ) codes are used to identify specific physical sites or buildings, such as central offices or remote terminals, within the geographic area. Assignment rules for this component are managed by operating company CLLI coordinators, who assign codes sequentially within each geographic area to accommodate new sites while maintaining global uniqueness. The structure supports up to 100 numeric sites or 676 alphabetic sites per geographic code, with updates required for mergers, relocations, or consolidations to prevent duplication and reflect changes in . This component refines the broader geographic prefix, enabling precise differentiation of multiple facilities in dense areas and facilitating applications like and . For instance, sequential numeric codes like "01" or "02" might distinguish adjacent central offices in a major city.

Equipment and Function Component

The Equipment and Function Component constitutes the final three characters of an 11-character CLLI Network Entity Code, precisely denoting the type and operational role of or functional entities at the specified site. This component builds directly on the preceding geographic and site/building identifiers to provide a complete description of elements. The structure of these three characters is deliberate: the ninth and tenth positions represent the function class, using two alphanumeric characters to categorize the 's primary role, while the eleventh position specifies a subclass, often a indicating priority or instance (e.g., "0" for primary). For instance, "DS0" identifies a primary switch, responsible for call routing and signaling in a central office environment, and "RS0" denotes a primary remote switch, which extends switching capabilities to distant locations via links. Over 200 such function codes exist, organized into categories by technology and application, encompassing switching, , and equipment. Function codes are assigned strictly according to the equipment's intended purpose and capabilities, independent of the manufacturer or specific model, to promote and across the . This approach has evolved to incorporate advancements, such as the introduction of codes like "" for terminals, which support high-capacity optical transmission systems. Telcordia (now ) maintains and updates these codes through its CLONES database, ensuring they reflect emerging technologies while preserving . By encoding functional attributes in this manner, the component facilitates targeted queries, allowing operators to identify sites with specific features—like switching for voice services or fiber optics for —essential for , provisioning, and .

Code Types

The four code types conform to the ATIS standard 0300253.2011 for Identification of Location Entities for Management.

Network Site Codes

Network Site Codes are 8-character variants of Common Language Location Identification (CLLI) codes designed to uniquely identify physical network sites, such as wire centers and headends, without specifying equipment or functional details. These codes provide a concise means for referencing general location information in contexts. The format of a Network Site Code consists of a 6-character geographic component followed by a 2-character site or building identifier. The geographic portion includes four alphanumeric characters representing the city or locality (e.g., "DNVR" for ), followed by two characters for the state or province (e.g., "CO" for ). The final two characters denote the specific site within that location, such as a central or building (e.g., "56" for a particular structure). This structure ensures global uniqueness for site-level identification while omitting the three-character equipment function suffix found in the full 11-character CLLI variants. These codes are primarily used for site-level references in network diagrams, inventories, and facility termination documentation, where brevity is prioritized over detailed equipment specifications. They are registered and maintained in centralized databases like the Common Language Operations Network Equipment System (CLONES) but are typically derived from the first eight characters of corresponding full CLLI codes. Unlike the extended 11-character Network Entity Codes, which incorporate equipment functionality, Network Site Codes focus exclusively on locational attributes to support efficient network planning and interconnection without functional granularity.

Network Entity Codes

Network Entity Codes in the Common Language Location Identification (CLLI) system are 11-character alphanumeric identifiers used to specify both the geographic location and the particular function or type of network equipment installed at that site. The structure consists of an 8-character base site code—comprising four letters for the city or place (e.g., NYCM for ), two letters for the state or province (e.g., NY for ), and two alphanumeric characters for the specific site or building (e.g., BG01)—followed by a 3-character entity code that denotes the equipment's role or type. For example, a code with the entity portion RS0 identifies a remote switching center located at the specified site. This format extends the base site code by appending functional details, ensuring precise identification of active components within telecommunications networks. These codes primarily serve to identify and track active elements, such as switches, multiplexers, systems, or antennas, in operations for tasks like provisioning and . They are essential for associating equipment with location-specific in industry databases, including those used for NPA/NXX assignments in the Local Exchange Guide (LERG) and for Automated Requests (ASRs) and Local Requests (LSRs) under ATIS standards. Entity Codes are the most prevalent CLLI format, supporting the management of core infrastructure in wireline, , and networks worldwide. Assignment and maintenance of Network Entity Codes follow strict rules to maintain accuracy and uniqueness. The 3-character entity code must precisely correspond to the type of physically installed at the site, with specific conventions such as two-letter prefixes for switching s (e.g., for digital switch) or single letters for non-switching elements (e.g., F for ). Changes to equipment or require re-registration through the Common Language Operations Network Entity System (CLONES) database, managed by , to update records and prevent discrepancies in operational systems. For certain network entity codes, characters B, D, I, O, T, U, W, and Y are prohibited in the eleventh position to avoid confusion, ensuring codes remain globally unique and interoperable across service providers.

Network Support Site Codes

Network Support Site Codes represent a specialized variant of Common Language Location Identification (CLLI) codes tailored for identifying non-building locations essential to operations. These codes target ancillary facilities that lack full structures, such as microwave sites, cable vaults, towers, telephone poles, manholes, fiber nodes, cable junctions, radio-equipment sites, , and toll stations. By providing unique identifiers for these distributed elements, the codes enable precise tracking, maintenance, and integration into broader network topologies without associating them to primary equipment buildings. The structure of Network Support Site Codes adheres to an 11-character format, beginning with the conventional 6-character geographic component—a 4-character city or locality identifier followed by a 2-character , , or geopolitical code—and concluding with a 5-character element specific to the support site. This 5-character portion incorporates a leading letter to denote the facility type, succeeded by numeric and alphanumeric details for uniqueness and attributes. For example, "P1234" designates a telephone pole, which integrates with geographic codes such as "DNVRCO" (, ) to yield a complete identifier like DNVRCOP1234. This configuration s detailed locational specificity while maintaining compatibility with the core CLLI geographic framework. Introduced in the amid the standardization of CLLI by Bellcore (now ), Network Support Site Codes addressed the rising need to catalog remote and outdoor infrastructure spurred by and transmission expansions. Assignment occurs through 's CLONES database, where licensees submit requests via to [email protected], and non-licensees utilize a formal Letter of Authorization procedure; codes are licensed with associated subscription and usage fees to ensure global uniqueness. These codes play a key role in ancillary network support by facilitating for elements like boundary crossings and end points, which are critical for interconnectivity and fault isolation in modern . Their use extends to vertical and horizontal coordinate associations for geospatial applications, enhancing overall reliability and .

Customer Site Codes

Customer Site Codes are 11-character CLLI identifiers specifically designed to denote end-user or premises within networks, distinguishing them from carrier-owned infrastructure. These codes facilitate precise location referencing for service delivery at customer sites, such as demarcations where carrier responsibility ends and customer equipment begins. The format consists of the first six characters representing the geographic location—four letters for the city or place name followed by two letters for the state or geopolitical entity—and the remaining five characters as a customer-specific identifier. For instance, "DNVRCO1A101" indicates a customer site in , , where "DNVRCO" denotes the geography and "1A101" specifies the customer element. This structure parallels network site codes but applies exclusively to non-carrier locations. These codes are primarily used to identify larger customer installations, including private branch exchange (PBX) systems, (CPE), and enterprise sites like universities, hospitals, or military facilities, but they are not assigned to individual residential locations. They support interconnection between carriers and customers, asset tracking, and regulatory reporting for services such as switched networks and installations. Assignment of Customer Site Codes occurs through service orders via the CLONES database, managed by , ensuring uniqueness by combining geographic elements with a distinctive five-character , often alphanumeric to denote the specific site type. Codes may include indicators like numeric sequences or abbreviations for the customer aspect and can be temporary during construction or initial setup phases before permanent assignment. The proliferation of Customer Site Codes accelerated following the , which promoted competition by enabling competitive local exchange carriers (CLECs) to interconnect with incumbent networks, necessitating standardized identification for diverse customer premises. Additionally, these codes incorporate privacy protections aligned with (CPNI) rules established by the Act, limiting the sharing of location data without customer consent to safeguard sensitive end-user details.

Applications and Usage

Service Provisioning and Ordering

Common Language Location Identification (CLLI) codes play a pivotal role in the provisioning and ordering of services by providing a standardized means to specify interconnection points and network elements in service requests. In the Access Service Request (ASR) and Local Service Request (LSR) processes, CLLI codes are mandatory for identifying serving wire centers, customer premises, and points of interconnection, ensuring accurate routing of circuits between carriers. For instance, when ordering interstate access services, carriers must include CLLI codes in ASRs submitted via systems like the Automated Circuit Service Ordering System () to designate endpoints, as outlined in industry guidelines. Similarly, in trunk provisioning, the Trunks Integrated Records Keeping System (TIRKS) relies on CLLI codes to assign and track interoffice trunk circuits, facilitating precise inventory management and order fulfillment. The integration of CLLI codes with (EDI) standards, adopted widely in the telecommunications industry since the early 2000s through frameworks like the Telecommunications Industry Forum (TCIF), enables automated electronic transmission of service orders, minimizing manual errors and accelerating cross-carrier setups. This automation is particularly critical for complex interconnections, where CLLI codes serve as unique identifiers for customer site codes—such as those denoting end-user locations—allowing systems to validate and route services without ambiguity. Carriers use these codes to comply with tariffs for interstate services, where precise location data is required to determine applicable rates and regulatory obligations, as specified in (FCC) filings. Furthermore, CLLI codes are essential for FCC-mandated (LNP), where they identify switches and points of interconnection during the assignment of Location Routing Numbers (LRNs), ensuring seamless of telephone numbers between providers. By standardizing location references, CLLI codes reduce provisioning errors in multi-carrier environments, supporting efficient , installation, and activation while adhering to industry-wide protocols.

Network Management and Call Tracing

CLLI codes play a crucial role in by providing standardized identifiers that link physical locations and equipment to Network Management Systems (NMS), enabling efficient fault isolation and status querying. Operators utilize these codes to pinpoint issues within the network infrastructure, such as querying the operational status of switches or transmission equipment at designated sites. For instance, interactive digital mapping tools powered by CLLI data allow visualization of , facilitating rapid identification and resolution of faults in operations. In call tracing applications, CLLI codes are used in the analysis of SS7-derived billing records and network logs to delineate call paths, helping operators reconstruct routes from originating to terminating points for diagnostic purposes. This integration supports detailed analysis of call flows, particularly in problems or verifying service delivery. Additionally, CLLI codes associate with V&H () coordinates, a for geospatial referencing, to enable distance-based routing calculations that optimize call paths and in traditional networks. A significant application of CLLI lies in emergency services, where the codes help associate calls with specific serving wire centers and facilities, contributing to accurate location identification and dispatch in public safety answering points (PSAPs) as of 2025. In fraud detection efforts, CLLI-enabled tracking of call origination points within billing and signaling data helps identify irregular patterns, such as unauthorized routing, enhancing overall . Since the early 2000s, CLLI codes have been adapted for -based networks through mappings that align traditional location identifiers with IP addresses and facilities, supporting hybrid environments and deployments as of 2025. This evolution ensures continuity in management and tracing functions as shift toward packet-switched architectures, with tools like TruOps Common Language providing geocoding and asset management across IP infrastructures.

Examples and Illustrations

Breakdown of Sample Codes

To illustrate the assembly of a CLLI code, consider the hypothetical network entity code DNVRCO56DS0, which follows the standard 11-character format for identifying locations and functions. This code is constructed as follows: the first four characters, DNVR, represent the geographical code for the city or locality (in this case, ). Positions 5 and 6, CO, denote the geopolitical code for the state or province (). Characters 7 and 8, 56, specify the network site or building identifier, here indicating a specific central office building. The final three characters, DS0, form the network entity code, signifying the function, such as a primary digital switch. This step-by-step composition ensures uniqueness across global networks by layering specificity with functional details. The geographical and geopolitical elements (positions 1-6) pinpoint the broader region, preventing overlap between similarly named places in different jurisdictions. The site code (positions 7-8) differentiates structures within that location, such as distinct or facilities. Finally, the entity code (positions 9-11) adds for or , allowing multiple devices in the same building to have distinct identifiers without . Each position adheres to alphanumeric constraints defined by industry standards to maintain consistency and machine-readability. A common variation is the 8-character truncation used for site-level references, omitting the entity code—for example, DNVRCO56 would refer solely to the central office building in , , without specifying internal equipment. This abbreviated form supports applications needing only locational data, while the full code enables precise equipment tracking. Overall, this modular structure avoids ambiguity in expansive infrastructures by combining hierarchical components into a compact, standardized identifier.

Real-World Applications

Common Language Location Identification (CLLI) codes are integral to telecommunications operations, enabling precise identification of network elements for various practical purposes. In service provisioning, CLLI codes facilitate the accurate specification of points of interconnection (POI) between carriers, streamlining the design and activation of services such as private lines and leased circuits. For instance, when ordering access services via Access Service Requests (ASRs) or Local Service Requests (LSRs), providers use CLLI codes to denote exact wire center locations, reducing provisioning errors and expediting interconnections. In network management and troubleshooting, CLLI codes support call tracing and fault isolation. Telecom operators employ them to track the origin and path of calls, particularly for resolving issues like annoying or harassing calls, by mapping CLLI identifiers to specific switching equipment and facilities. This application is crucial in operations support systems (OSS), where CLLI data integrates with master data management to validate addresses, geocode sites, and minimize duplicate entries—such as distinguishing "Main St" from "Main Street"—thereby cutting operational costs and survey needs. Regulatory compliance represents another key application, particularly in emergency services and carrier designations. The Federal Communications Commission (FCC) utilizes CLLI codes in administering pseudo-Automatic Number Identification (pANI) for 9-1-1 systems, where they identify selective routers to ensure emergency calls route correctly to Public Safety Answering Points (PSAPs). In pANI request forms, providers specify the selective router's CLLI code to assign identifiers accurately in multi-router setups. Additionally, state public utility commissions and the FCC reference CLLI lists to define eligible telecommunications carrier (ETC) service areas and forbearance from unbundled network element (UNE) regulations, as seen in designations for wire centers in price cap local exchange carriers. Beyond core , CLLI codes aid in broader infrastructure planning. The () has noted their use in analyzing Telcordia-maintained location registries for market assessments, such as evaluating deployment and . For example, tools like GeoResults leverage CLLI data to map network coverage, supporting federal oversight of obligations. These applications underscore CLLI's role in enhancing efficiency, accuracy, and across global networks.