Domain Name System Use Standards

Issued April 7, 2014, from IT Infrastructure Services.

Questions about this standard can be addressed to


The Domain Name System (DNS) is a distributed database system used to translate hostnames (i.e., to IP addresses (i.e., and to translate IP addresses back to hostnames. The Internet Architecture Board has delegated global authority for the DNS to several top-level registries. These registries further delegate authority for portions of the DNS to sites on the Internet and may, in turn, have portions of their namespace delegated to other entities.

At Purdue University, authority for the namespace has been delegated to IT’s Infrastructure Services (ITIS) group. ITIS is responsible for the smooth operation of the Purdue DNS and works with other departments to coordinate changes and manage resources for the benefit of the University as a whole.

The purpose of this standard is to provide clarity for users of the Purdue University DNS and to maintain consistency in the practice of selecting and naming the domains of services and organizations at Purdue University.


Top-Level Host Names

A top-level host name is a host name in the namespace that is not a member of any subdomain (e.g., In general, host names belong inside subdomain names associated with the owning organizational entity. However, some hosts provide services to the University community and do not properly belong in a subdomain. These hosts must be owned or administered by an officially recognized University organization. Purdue host names may not be registered to a non-Purdue network resource or IP address.

The procedure for applying for a top-level host name is set forth in the Procedures for Use of the Domain Name System at Purdue University document.


Each University organizational entity is entitled to one subdomain of The subdomain name shall reasonably reflect the name of the organizational entity and must conform to the naming conventions detailed below under the University Naming Convention section. These names shall not overlap with other organizational entities so that there is no confusion about what subdomain a host should be part of.

For example, there should not be An exception to this practice may occur when the school provides central resources for its member departments that are owned and administered separately from departmental resources.

The Domain Oversight Committee must approve any exceptions to this practice in writing.

Student Organizations

Recognized University student organizations are not entitled to a subdomain. Student organizations may register hosts within the subdomain. Host names should reflect the student organization’s name. A recognized student organization may qualify for a top-level host name in some circumstances.

The procedure for registering names for student organization machines and the procedure for applying for a top-level host name for a student organization are set forth in the Procedures for Use of the Domain Name System at Purdue University document.

Foreign Domain Names

Purdue University recognizes that foreign domain names may be required or desired by various organizational entities. When these names are associated with devices on the West Lafayette campus network, the official registered name of the machine must be an appropriate name. All foreign names will be aliases of this official name. ITIS must be notified in advance of foreign domain name use.

The procedures available for utilizing foreign domain names are set forth in the Procedures for Use of the Domain Name System at Purdue University document.

University Naming Convention

In addition to any requirements specified above, all names for subdomains, hosts, or foreign domains must conform to the following technical requirements:

  • Each label must consist of only letters, numbers, and the hyphen ('-') character. Each label must start and end with a letter or number.
    • Note: Letter case-sensitivity is not significant.
  • Any single label may not be more than 63 characters long.
  • The entire name may not be more than 255 characters long.

Subdomain names shall be at least three characters long to avoid potential security issues and user confusion. All existing two-letter subdomain names may continue to exist. 

Top-level domains in the DNS shall not be used as host or subdomain names because of potential security issues and the confusion that they may cause. Examples of top-level domains in the DNS include: .com, .edu, .gov, .mil, .net and .org.

All names for subdomains, hosts or foreign domains are a reflection of Purdue University. Good taste should be used in name selection. Names should not be misleading, whether intentionally or not, to a person reasonably familiar with the University. Names may not infringe on any copyrights.

In addition, all names must comply with all University policies and applicable departmental policies and procedures, such any style standards issued by Purdue Marketing and Media, where applicable. All name services will be provided by the centrally run DNS server except as approved by the Executive Director of ITIS.


Centralized and departmental IT units, IT Resource owners and those individuals requesting subdomains, hosts, or foreign domains are responsible for ensuring appropriate enforcement of this standard and related standards on University IT Resources within their areas of responsibility.

The formal Security Policy Exception Procedure must be followed for any exceptions to the requirements stated in this standard. The Executive Director of ITIS, or his or her designee, must approve any exceptions to the requirements stated in this standard.

Purdue Marketing and Media is responsible for ensuring the correct use and integrity of the Purdue seal and mascot logo on all University publications, supplies, materials and equipment, whether produced by the University or an outside agency. Any questions about appropriate use of the seal and mascot logo should be directed to the office at  765-494-2034.

Domain Name Definitions


A domain or domain name is any name in the DNS regardless of its location in the tree. At Purdue University, the term domain typically refers to the top level of the namespace delegated to Purdue, namely

Domain Name System

The Domain Name System (DNS) is a distributed database system structured as a collection of trees. Each branch of the tree is assigned a label to further distinguish it from its siblings. At the leaves of the tree are individual hosts each of whose names is the concatenation of all labels leading back to the root separated by a period or dot. This chain of labels forms a unique name within the global DNS. For example, consists of the three labels www, purdue, and edu.

Foreign Domain

A foreign domain is any domain in the DNS space that is maintained by Purdue University that is not part of the namespace.

Host (or host name)

The DNS does not strictly define the term host, but in common usage, it is used to describe a leaf of the namespace.


The entity responsible for managing domain name records within the Purdue Domain Name System. Hostmaster at Purdue is maintained by IT Purdue Systems Security. All questions about the Purdue University DNS, host registration requests, or other requests designated in this document must be directed to the Purdue University Hostmaster at


IPAM (IP Address Management) is software or a device that aids in the management of DNS and DHCP addresses. In this instance, it includes delegation of management down to a departmental level to allow groups on campus some control over the addresses that have been assigned to them.


A portion of a domain, subdomain, or host name between the start of the name and the first dot, between any two dots, or between the last dot and the end of the name.


An address space delegation from a central registry. Examples of networks at Purdue University are and

Organizational Entity

A department, school, or other independently identifiable portion of Purdue University. An organizational entity typically has a department number or a separate account (or collection of accounts) in the University's accounting system.


The DNS does not strictly define the term subdomain, but in its common usage, it is used to describe a non-leaf sub-tree of For example, in the name, is a subdomain name.

Subnetwork (Subnet)

A portion of a network that can be used as unit of delegation and routing. Subnets at Purdue typically use 24-bit masks, so the subnet number can be readily determined from the third part of an IP address. For example, is subnet 11 of

Top-Level Host Name

A top-level host name is a host name in the namespace that is not a member of any subdomain. For example,

Related References:

  1. University IT Policies are available at: 
  2. Standards supporting the implementation of University IT Policies are available at:
  3. Security Policy Exception Procedure, available at:

Issued January 14, 2011, from IT Purdue Systems Security. Questions about this standard can be addressed to

Revised November 21, 2011, to update URLs.

Revised April 7, 2014.