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TNS Policies

Editing DNS Host Files

Resource Record Types

Addendum

Proper Format of DNS Update Requests

In order to facilitate the process of editing DNS host files, the Policy Regarding the Operation of Domain Name Servers in the PSU.EDU Domain states that all requests for name server additions or changes be received in DNS Standard Resource Record Format. Name Server registration requests must be in Standard Resource Record Format or they will be sent back to the requesting party without being added to the DNS database. Requests for deletions need only specify host name and IP address.

The following example text illustrates Standard Resource Record Format. The breakdown of the format is explained in the notes which follow the example entries.

There are four different Resource Record types illustrated here:

1. An address record consists of a name (host name, alias or mail exchanger name), a record class ("in" for Internet), a record type ("a" for address) and a data field (in this case the IP address). Fields are separated by tabs.
2. A host information record consists of the "in" record class, an "hinfo" (Host Information) record type, and a data field of two required elements: host hardware type and operating system type.
3. An alias record consists of an alias name, an "in" record class, a "cname" (Canonical Name) record type, and a data file giving the real host name to which the alias points.
4. A mail exchanger record consists of a name, an "in" record class, an "mx" (Mail Exchanger) record type, and a data field of two elements: a positive integer representing a relative preference value when selecting among alternate mail exchangers (the lower the integer value, the higher the precedence, with 0 being the highest) and the real name of the host to which the mail should be directed.

In order to facilitate the process of DNS Integrated Backbone Service requests, it is TNS' policy that all such requests be submitted by an authorized Administrative, Technical, or Security Contact specified on the Penn State Data Backbone Contact List via the applicable Integrated Backbone Services Request Forms that reside on a secured server. These forms can only be accessed by an authorized Backbone Contact.

Addendum

The Domain Name Server resolves user-generated host and subdomain names to IP addresses from entries in the format illustrated in the above example. This is called "forward" lookup. In order to resolve IP addresses to corresponding host and subdomain identities, DNS also maintains "inverse" lookup records.

It will also henceforth be TNS policy with respect to DNS update requests that the inverse lookup records be included in the request. The format of the inverse lookup records is given in the following example, which uses the host names from the forward lookup example given above. For the sake of illustration the example.psu.edu has been used as the fictitious subdomain name of the listed hosts:

A DNS inverse entry is a single Resource Record type called a pointer record. A pointer record consists of an IP address given in reverse order (host number and subnet number only), an "in" record class, a "ptr" (pointer) record type and the fully qualified host name (host.subdomain.psu.edu. The final trailing "." must be included).

Because the inverse entries go into a completely separate file from the forward entries, they must be included in the update request in a separate list from the forward lookup entries. Pease do not submit them as simply another line added to the forward lookup entry.

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