Wholesale: Products & Services

CenturyLink™ Local Services Platform (CLSP™) - Centrex - V9.0

Note: This product is also known as Qwest Local Services Platform® (QLSP®).

Note: Effective July 20, 2017, all CLSP Centrex products are grandfathered in all states and are no longer available as a new service. Changes to existing services are also prohibited with the exception of disconnect requests. Some Centrex products were previously grandfathered in some states.

History Log

Product Description

CenturyLink™ Local Services Platform (CLSP™) products provide local exchange telecommunications services to end-users on behalf of Competitive Local Exchange Carriers (CLECs) at competitive wholesale commercial rates. General information about CLSP can be found in CenturyLink™ Local Services Platform (CLSP™) - General Information.

CLSP Centrex 21, CLSP Centrex Plus, and CLSP Centron provide exchange services between your end-user's premises and the CenturyLink Central Office (CO) that are functionally equivalent to CenturyLink's retail Centrex service offerings. CLSP products are finished services requiring neither CLEC collocation nor other CLEC network involvement, and are combinations of the following network elements:

  • A 2-Wire Analog (Voice Grade) Unbundled Local Loop
  • An Analog Line Side Port, including Local Switch Usage and any optional switch features(Local Switching Network Element)
  • Shared Transport
  • Network Access Registers (NARs) on CLSP Centrex Plus and CLSP Centron

CLSP Centrex 21 is a business service providing access to 21 different standard and optional features and is intended for end-users with 2 to 50 station lines per location. Standard features are available to all station lines in the shared customer group.

A common block is a dedicated space in the CO that is provisioned to contain certain specified standard features that are available for all station lines. CLSP Centrex 21 provides a pre-provisioned common block containing specified standard features that are available for all station lines. The standard feature package and optional feature availability may vary from state to state. For all packages, plans and features view the Tariffs/Catalogs/Price Lists.

CLSP Centrex Plus and CLSP Centron services are central office based business communications services with state-of-the-art capabilities and features provisioned by the use of local network transport technologies. A group of station lines is translated for an individual customer group and provides common access to a predetermined group of system features. All station lines in the system have intra-system calling capability. A choice of access to the local exchange calling area via each station line (non-blocked) or controlled access line (blocked) depends upon the number of subscribed NARs. Touchtone, Automatic Identified Outward Dialing, Direct Inward Dialing (DID®), and Individual Line Billing are inherent with the service and are automatically programmed within the station line.


CLSP products are available where facilities exist throughout CenturyLink QC. CLSP Centrex is not available as a new service and changes to existing services are prohibited with the exception of disconnect requests.

Terms and Conditions

Line Splitting is available with CLSP Centrex. Information is available in Line Splitting.

The minimum requirement for Centrex 21 service in all CenturyLink states is two (2) lines. A partial conversion of existing Retail or Resale Centrex 21 service to CLSP Centrex 21, or a move/change of existing CLSP Centrex 21 may cause the service to fall below this two line minimum requirement. When you submit a Local Service Request (LSR) that results in a Centrex 21 service falling below the two- line minimum, you must mark the request for manual handling and provide instructions in the REMARKS field regarding the remaining service, including alternative service type, desired features, etc. If instructions are not provided, CenturyLink will convert the remaining line to the current platform POTS service with no features. If CenturyLink broadband is present on the remaining line, it will be retained.

CLSP Centrex 21 is pre-provisioned with Assumed Dial 9 in the common block (which means all outgoing calls are dialed directly on the switched network, not within the common block). Therefore, 4-digit dialing to another Centrex 21 station and dialing plans of less than 7 digits is not possible.

All CLSP Centrex Plus and CLSP Centron station lines must be associated with the main switching equipment. The Centrex or Centron system may be either blocked or non-blocked, however they cannot be mixed. Combined station lines terminating at different locations into a single system must be served by the same CO.

Telephone numbers (TNs) for Centrex Plus must be ordered in blocks, either through your Service Manager or via a request to the Interconnect Service Center. TNs for Centrex Plus may not be reserved through EASE-LSR.

Technical Publications

Technical characteristics are described in:


Rate Structure

Monthly Recurring Charges (MRCs) for CLSP Centrex lines are the sum of the monthly recurring rates of the following elements:

  • A 2-Wire Analog (Voice Grade) UBL, provided in the Rate Sheet or Exhibit A of the applicable ICAs in effect between CenturyLink and CLEC,
  • The Local Switching Network Element Analog Line Side Port (including the switch port MRC plus Local Switching Minutes Of Use (MOU), provided in the CLSP Rate Sheet,
  • Switch Features and Common Block provided in the CLSP Rate Sheet,
  • Shared Transport MOU provided in the CLSP Rate Sheet, and
  • Any additional MRCs for other value added services, such as Operator Service (OS)/Directory Assistance (DA), CenturyLink Voice Messaging Service (VMS), Advanced Intelligence Network (AIN), etc., provided in either your ICA and/or CLSP Rate Sheets

The MRC for NARs will be zero ($0) rated for CLSP Centrex products.

Non-recurring Charges (NRCs) for CLSP are provided in the CLSP Rate Sheet.

CLSP Centrex products include either one residential or one business directory listing (dependent on end-user application and the product requested) for each main telephone number, at no charge. Premium and privacy listings are also available. Regardless of residential or business directory appearance, all premium and privacy listings (with the exception of residential additional listings, i.e., Universal Service Order Code (USOC) RLT) are categorized as business for rating purposes. Information describing directory listing availability and ordering is described in White Pages Directory Listings.


MRCs and NRCs are available in the CLSP Rate Sheet of your Commercial Agreement and the Rate Sheet or Exhibit A of the applicable ICA.

The following NRCs are applicable when you request product changes related to Centrex services:

  • CLSP Centrex Plus/Centron Installation NRCs apply when you request conversion of an existing POTS service, e.g. Resale 1FB, to CLSP Centrex Plus/Centron.
  • CLSP Centrex Plus/Centron Installation NRCs apply when you request conversion of lines from another Centrex Plus Common Block, e.g. Resale or Retail Centrex Plus, to CLSP Centrex Plus, unless you request conversion of the entire Common Block.
  • CLSP Centrex 21 Conversion NRCs apply when you request conversion of an existing POTS type service, e.g. Resale 1FB, to CLSP CTX 21.

Nebraska CLSP circuits only:

Effective September 19, 2011, you must place either the USOC XCBO2 (2-wire) or XCBO4 (4-wire) on your CLSP LSR if your End-User is in an "Out of Town" location. Additional information on determining this classification is in Geographic Deaveraging - General Information.

Tariffs, Regulations and Policy

Tariffs, regulations and policies are located in the state specific Tariffs/Catalogs/Price List.

Contract Service Arrangements (CSAs) for existing resale or CenturyLink retail service will be terminated if the service provided under a CSA is converted to CLSP Centrex service. Termination liability if applicable, provided for in the CSA, will apply and will be billed to you or to the CenturyLink retail end-user that is involved with the CSA.

Optional Features

A complete list of product specific features, descriptions, availability, pricing, and ordering information is available in the Features Matrix download available under the Optional Features section of CenturyLink Local Services Platform (CLSP) - General Information.

Electronic Business Set (EBS)/Meridian Business Set (MBS) Service permits the use of special electronic station sets in conjunction with Centrex 21, Centrex Plus, Centron provided in DMS -100 switches. This service utilizes a unique line card to provide communications control for the electronic station set. EBS service has a variety of features available to be programmed on the station set. For availability and feature information contact your CenturyLink Service Manager.

The following optional system features may be available with CLSP Centrex Plus and CLSP Centron and can be requested by contacting your CenturyLink Service Manager.

  • 800 Service
  • Account Codes
  • Attendant Access Line Service
  • Attendant Set Interface
  • Automatic Call Transfer
  • Authorization Codes
  • Automatic Call Back
  • Automatic Route Selection
  • Call Forwarding - Outside
  • Call Forwarding via Private Facilities
  • Call Waiting - Intragroup 3
  • Call Waiting - Originating
  • Camp-On and Call Waiting Originating Options
  • Centrex Management Systems
  • Circuit Connections
  • Data Call Protection
  • Dial Dictation
  • Digital Facility Interface
  • Direct Inward System Access (DISA)
  • Distinctive Ringing/Distinctive Call Waiting
  • Executive Busy Override
  • Individual Line Billing
  • Last Number Redial
  • Loud Speaker Paging Trunk
  • Make Set Busy
  • Multiple Position Hunt
  • Music On Hold
  • Network Speed Call
  • Night Service Arrangement
  • Night Service (Trunk Answer Any Station)
  • Outgoing Trunk Queuing
  • Primary Directory Number
  • Secondary Directory Number
  • Station Message Detail Recording (SMDR)
  • Time of Day (NCOS)
  • Time of Day Routing
  • Trunk Answer Any Station (Night Service)
  • Trunk Verification From Any Station
  • Uniform Call Distribution

Dual Service allows an end-user that is moving within the same wire center to maintain the same telephone number for up to 30 days at both the new address and the old address. Dual Service is available where facilities permit with CLSP Centrex 21.


CLSP Centrex 21

  • A variety of standard and optional features enable robust call management which provides your end users significant business efficiencies.
  • A flexible communications system allows line or feature addition and removal as the needs of your end user's business evolves.

CLSP Centrex Plus and Centron

  • Local network transport technologies fit seamlessly with other telecom and data services
  • Service is configured/translated specifically for your end-user's needs and allows common access to a predetermined group of system features and intra-system calling capability.


CLSP Centrex products provide you the opportunity to purchase the finished services that your end-user markets desire at competitive, commercial, market-based rates.


Product Prerequisites

If you are a new CLEC and are ready to do business with CenturyLink, view Getting Started as a Facility-Based CLEC and Interconnection Agreement, and Commercial Agreements.

If you are an existing CLEC would like to amend your Interconnection Agreement or New Customer Questionnaire, refer to Interconnection Agreement Amendments. To review and/or request preparation of a CLSP Agreement, visit Commercial Agreements.


General pre-ordering activities are described in the Pre-Ordering Overview.

Requirements for pre-ordering are described in Local Service Ordering Guidelines (LSOG) Pre-Order.

To request new CLSP Centrex Plus or CLSP Centron service, contact your CenturyLink Service Manager for assistance with identifying functionality requirements and to request a common block built in the switch where you want to provide service. Before ordering any optional, standard, or system features, you must verify if the feature is built into the common block. Features that are not built into the common block may be requested through your CenturyLink Service Manager.

Notify your CenturyLink Service Manager if you would like to convert your resale or retail Centrex to CLSP Centrex prior to submitting your request.


It is important to review and understand the ordering procedures described in CenturyLink Local Services Platform (CLSP) - General Information.

General ordering activities are described in the Ordering Overview.

Disclosure Information and other Local Service Ordering Guidelines (LSOG) are available in Network Disclosures.

Intervals for conversions from retail or resale Centrex to CLSP Centrex of 50 or more stations will be handled on an Individual Case Basis (ICB). Once a due date is assigned CenturyLink will establish a moratorium on other account activity during the conversion.

Requests for CLSP Centrex are placed using the EASE-LSR Graphic User Interface (GUI) or EASE-LSR Extensible Markup Language (XML). You may also submit the completed LSOG forms to CenturyLink by facsimile to (888) 796-9089. Detailed information regarding field entry requirements are described in the LSOG.

The following LSOG forms may be required:

  • LSR
  • End User (EU)
  • Centrex Resale Service (CRS)
  • Directory Listing (DL)

When requesting a full conversion to CLSP Centrex 21 service from other existing, e.g. Resale, Centrex 21 service, using the LSR ACT Type = V, all listings on the current account must be addressed using applicable LACT values or the listing will be rejected. If there are no change(s) to the listing(s), the listing(s) should have the LACT value of Z. If the LSR ACT Type = V, and a LACT value of Z is present on the DL form, the TN will be used for validation purposes, but all other information on the DL form will be ignored. The listing will remain exactly as it exists on CenturyLink's Customer Service Record. If any change(s) are made to a listing(s), then LACT O, I, or D values should be entered. LSRs with 'LACT = N - New Listing' selected when changes are being made to existing listings will be manually rejected by CenturyLink. Only new listings may be added with LACT = N during conversion activity. Existing listings may be deleted during conversion activity with LACT = D - Delete Listing.

In addition, if any change(s) are made to any existing listing(s) using LSR ACT = C, T or R, then LACT = O, I or D values should be entered.

When converting an existing account with CenturyLink Broadband to CLSP Centrex, follow the requirements in the Ordering section of CenturyLink Commercial Broadband Service.

CLSP Centrex 21 end-users share a common block within the CO. As a result, all end-users share the functionality of the common block. The common block name must be provided in the Common Block (CB) field on the CRS.

Generic CLSP Centrex 21 common block names by switch type:

Switch Type Common Block Name
5ESS® IDP2100
DMS-10 21
DMS-100 CTX2100:0
Ericsson 2100

Some DMS-100 Remote switches may carry a different Common Block name than is shown above. If you have any questions as to whether or not the standard Common Block name for the CO is applicable, contact your CenturyLink Service Manager.

A Line Class Code (LCC) identifies the originating and terminating calling restrictions or combinations of calling restrictions for a line and is stored in the common block memory of the program controlled switch. The LCC must be entered in the FEATURE DETAIL field on the CRS form.

To verify whether or not to use the BLOCK field or assign a specific LCC on the CRS form, see the Blocking Job Aid.

For additional information on Centrex LCCs, refer to the Centrex Line Class Code (LCC) Job Aid. The tables in this job aid are provided for informational purposes only and are a sampling of the most commonly used LCCs for each of the Centrex products. The appearance of an LCC in one of the tables does not mean that it is available to be assigned to your Centrex accounts. If you have any questions regarding the availability of a particular LCC, please contact your CenturyLink Service Manager.

A Customer Access Treatment (CAT) Field Identifier (FID) is assigned for each station line in a common block and allows a station line to access system features using dial access codes. The CAT FID must be entered in the Line Treatment Code (LTC) field for each station line on the CRS.

In all switch types other than the DMS-100, there is only one CAT FID assigned to the switch at the account level. The CAT works in conjunction with the individual LCC for the type of calling restriction requested.

In the DMS-100, different CAT FIDs can be assigned at the line level rather than at the account level. The calling restriction type is derived from the combination of the CAT and LCC. The CAT FID identifies the calling restrictions for outgoing calls and the LCC identifies the incoming calling restrictions.

DMS-100 CAT FIDs and corresponding LCC:

CAT FID Description of CAT* Corresponding LCC
0 Non-restricted: No restrictions are placed on the line, the end-user can make and receive all calls. NCN
2 Long distance restricted: The end-user can place outgoing local calls, including DA 411, they cannot dial any 1+ or 0+ calls and can receive all incoming calls. NCT
4 Non-restricted (Block 900/976): The end-user can make all local and long distance calls with the exception of 900/976 calls and can receive all incoming calls. NC9
6 Restrict DA (411 & 1+555): The end-user can make all local and long distance calls with the exception of DA 411 and 1+555. They can receive all incoming calls. C3R
7 Toll restricted Deny DA: the end-user can place outgoing local calls, they cannot dial any 1+ or 0+ calls, or calls to DA 411 or 1+555. They can receive all incoming calls. NCB
8 Restrict DA (411 & 1+555) and (Block 900/976): The end-user can make all local calls with the exception of DA 411. They can make all long distance calls except 1+555 and 900/976 and can receive all incoming calls. D3R

* If the calling restrictions you are interested in are not shown above, contact your CenturyLink Service Manager for assistance.

5ESS, DMS-10 and Ericsson CAT FIDs

Switch Type CAT FID
5ESS 1
DMS-10 0
Ericsson 0

Conversions from resale or retail Centrex to CLSP Centrex are submitted according to the LSOG for a Conversion As Specified request. There are two conversion options:

  • A single local service request converting an entire common block without a line, feature or PIC/LPIC change. Line, feature and PIC/LPIC changes can be made on subsequent local service requests.
  • Individual per end-user, per location conversions requiring multiple local service requests. You must specify on each local service request whether you want to retain, change or remove each line and feature along with any PIC/LPIC changes.

You must request removal of features not available with CLSP products prior to conversion activity.

You are required to enter project identification in the PROJECT field on the LSR form for all conversions from resale or retail Centrex Plus/Centron to CLSP Centrex Plus/Centron.

More information about selecting a long distance carrier can be found in the Long Distance Carrier Selection Overview.

Provisioning and Installation

General provisioning and installation activities are described in the Provisioning and Installation Overview.

Maintenance and Repair

General maintenance and repair activities are described in the Maintenance and Repair Overview.


Customer Records and Information System (CRIS) billing is described in Billing Information - Customer Records and Information System (CRIS).

  • The CLSP Centrex 21 Class of Service (COS) is RH2XX.
  • The CLSP Centrex Plus COS is RHCXX.
  • The CLSP Centron COS is RHBXX.


CenturyLink has developed and provides an array of training courses that our CLSP customers will find beneficial. The following courses are especially recommended:

  • Local CenturyLink 101: "Doing Business with CenturyLink"
  • Centrex Systems
  • EASE-LSR Directory Listing
  • EASE-LSR "Hands On"
  • POTS Product Overview
  • CLSP Centrex via EASE-LSR

View these and additional CenturyLink courses by clicking on Course Catalog.


CenturyLink contact information is located in Wholesale Customer Contacts.

Frequently Asked Questions (FAQs)

1. How do I submit local service requests?
CLSP orders may be placed using the EASE-LSR GUI, the EASE-LSR XML or by submitting the completed LSOG forms to CenturyLink via facsimile at (888) 796-9089.

Last Update: July 20, 2017

5ESS® is a Registered Trademark of Lucent Technologies, Inc.
Centron®, CenturyLink™ Local Services Platform, and CLSP™ are Trademarks of CenturyLink™
DID® is a Registered Trademark of CenturyLink™
CLASS™ is a Trademark of Telcordia Technologies, Inc.
DMS™ is a Trademark of Nortel Networks.