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U.S. Army URN Repository Overview
Written by Frank J. Ponzio, Jr.

Unit Reference Numbers (URN) are unique identifiers up to eight digits in length used to identify units, equipment, organizations, vehicles, and messaging groups.  They are used in data products throughout all the Federal Government’s Service Agencies, primarily in the Army, Navy, Air Force and Marines.  URNs can be thought of as IP addresses specific to the Service Agencies’ missions; each one must be unique in order for the systems to communicate properly.

Historically, Army C4I and Simulations Initialization System (ACSIS) has been the assigner of all U.S. Army URNs, similar to the functionality of the Internet Corporation of Assigned Names and Numbers (ICANN) responsibility for IP Address assignments on the Internet. Unfortunately, no service-wide mandate, similar to the ICANN standards, exists to ensure the proper allocation and maintenance of URNs. As a result, many issues currently face the URN user community today, including duplications, unregistered URNs, and non-standard URN assignments.

The driving force behind standingup the U.S. Army URN Repository (AUR) is the need to mediate existing URN assignments and develop a clean data set in support of current initialization data product development. The most difficult challenge in standingup the AUR will be the mediation of URN assignments and the establishment of a services-wide infrastructure to allocate and maintain unique URNs, as the data is enterprise-wide, and any potential changes harbor significant ripple effects across internal Army organizations.


The AUR was developed as a solution to the Army’s ongoing issues with URN mismanagement and to support Joint Forces Command (JFCOM) initiatives by supplying the Joint URN Repository (JUR) with validated Army URN data.

Late spring 2006, Joint Forces Command solicited proposals from each service agency to design and build the JUR. The Army’s proposal submitted by Product Manager, Network Operations – Current Force (NetOps) was not accepted as the solution for the JUR, but formed the basis for the AURproject. Leveraging the requirements JFCOM developed for the JUR, NetOps contracted Symbolic Systems, Inc. to deliver the AUR 1 June 2007.

As of 1 June 2007, the AUR is available for operation and is currently undergoing government freeplay.Concurrently, AUR data mediation (DM) is also being performed by Symbolic Systems, Inc. Ultimately, the results of AUR DM will provide a clean data setto publish to the AUR and JUR, as well as mediation of new URN assignments to prevent URN issues downstream in the data product development process.

Understanding URNs

A URN is structured and exchanged as a 24-bit binary coded number, allowing a maximum total of 16,777,216 (decimal) unique URNs. Each Service Agency utilizes the URN, therefore ranges have been assigned to avoid misuse.Below are the URN ranges by agency as defined by MIL STD-VMF-6017.

Organization URN Block
U.S. AIR FORCE BLOCK 3000000 THROUGH 3999999
U.S. NAVY BLOCK 4000000 THROUGH 4999999
UNDEFINED 8000000 THROUGH 16777213
Reserved 16777214 INTELLIGENCE REPORT.
Reserved 16777215 RESERVED FOR MIL-STD-2045-47001 USE

Table 1. MIL STD-VMF-6017 URN Ranges

Overtime, the URN has become multi-faceted and been utilized for a number of reasons. This has caused the URN to take on a ‘type’ classification.Currently there are varied URN types, such as Broadcast Groups, Multicast Groups, Units, Reserved, Blue Force Tracking, Upper and Lower Tactical Internet, and Non-Digitized.


The AUR operates as an online repository harboring URNs validated by Subject Matter Experts (SME) for usage by select U.S. Army personnel. To develop a clean data set the AUR Data Mediation Team, comprised of URN SMEs, mediates URNs from the following sources:

  • NetOps data products (LDIF & Address Book)
  • PM FBCB2 data products (EPLRS & BFT Databases)
  • Battle Command Sustainment Support System (BCS3) feeds
  • JMUL/AFTADS feeds

Leveraging AKO Single Sign-on capabilities, the AUR is available to users via the Internet and is accessible through both the personal computer and BlackBerry. Below is a diagram that depicts the basic interactive nature of the AUR.


Figure 1. U.S. AUR Operations

The AUR data will include the following six mandatory fields (designated by JFCOM), in addition to other non-mandatory fields. The fields are

  • URN
  • Unit_Short_Name
  • Unit_Long_Name
  • Service/Agency
  • Nationality
  • MIL-STD-2525_Symbol_Code

Users can access URN data by querying the repository. Depending on the level of access rights, users can

  • Query the repository for single or multiple records and view results
  • Modify or update existing records
  • Delete existing records
  • Create new records
  • Publish bulk updates of records
  • Print out reports
  • Download reports/data in XLS, CSV, and DAT formats


The implementation of the AUR provides the Army with a single, authoritative data source for valid URN assignments. It will also be the first database to consolidate the entire range of Army URNs, providing further insight into the nature of the data.

Ultimately, the improvement of URN data will yield higher quality data products, while reducing the number of attempts and time required to develop data products. In addition, by inserting the AUR DM Team into the data product build process, new URN assignments made in data product production can be mediated upfront, reducing rework and issues in the build process.

Once the AUR is completely populated with existing URN assignments and the Army has a clear picture of its URN assets, concepts such as block URN assignments and permanent assignments can be further explored.


As the repository is populated with clean data over the coming months, the AUR is expected to make a significant impact on URN management for the Army. In addition, URN mediation will improve the data product build process at NetOps, while reducing build-cycle durations and improving quality.

As a whole, the Army will benefit by properly managing its URN data and by fulfilling JFCOM/JUR requirements in support of joint operations, ultimately yielding a better equipped Warfighter.

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