DNS Defined - Getting Started with DNS


Acquiring the Software

Some TCP/IP software includes DNS as part of its product. For example, Process Software Corporation's TCPware product includes DNS in its Domain Name Services as a base product feature. Most commercial UNIX vendors include the BIND (Berkeley Internet Name Domain) implementation.

If you’re interested in getting the newest BIND source code, it's available to DNS-registered hosts by anonymous FTP at FTP.UU.NET (address in the directory /networking/ip/dns/bind.


Host System Administrator Responsibilities

The host system administrator’s responsibilities to maintain the domain are to:

  • Define the administrative zone's boundaries.
  • Provide the zone data master files.
  • Update the master files.
  • Determine the zone's refresh policies.


Domain Administrator Responsibilities

The domain administrator’s responsibilities are to:

  • Coordinate activities with the parent domain and subdomains.
  • Manage the domain and be aware of complaints, problems, and protocol violations, and be able to deal with them responsibly.
  • Ensure service is reliable and current.


Setting up a Domain

You can set up a domain name for your organization and specific networks and hosts within it only after you:

  • Find out where you fit in the current domain namespace.
  • Determine if your network number is registered with NS.INTERNIC.NET.
  • Register with your parent domain.
  • Set up a reverse mapping in the IN-ADDR.ARPA domain.

According to RFC 1034, once you choose a name for a zone you administer, you should be able to demonstrate that you have a primary and at least one secondary master. A server doesn't need to be on a host with a name in that domain. In fact, it's best if at least one server is outside the domain.

For some guidelines on setting up a domain, see RFC 1032, Domain Administrator's Guide, or RFC 1033, Domain Administrator’s Operations Guide, available on the Internet.


Fitting in and Choosing a Domain Name

Suppose you want to set up a domain for the PLATO.PROCESS.COM network of hosts. A good starling point is the root name server for the domain (you are not alone: users query “roots” an average of almost 400 times a second over the Internet). You can go to the root using the nslookup utility, which extracts information from DNS servers:

> root
Default Server:	ns.internlc.net

Look for name servers in the PROCESS.COM. domain (note the dot at the end of process.com. to make the domain name fully qualified and not relative to your local domain):

> set type=ns	; set the type to Name
> process.com.
Server:	ns.in.ternic.net

Non-authoritative answer: 
process.com        nameserver = BU.EDU
process.com        nameserver = SIRIUS.process.com
process.com        nameserver = NIC.NEAR.NET

Authoritative answers can be found from:
BU.EDU 	internet address =
SIRIUS.process.com	internet address =
NIC.NEAR.NET	internet address =

You can then query one of the name servers listed, such as SIRIUS.PROCESS.COM. Each domain name field is a label that can range from 0 to 63 bytes (known as octets to DNS), although the shorter the label the better. In fact, 12 characters is a suitable maximum. Each label must start with a letter and can be followed by alphanumeric characters (a to z, A to Z, or 0 to 9), or hyphens. Labels end with an alphanumeric character. Although labels aren't currently case-sensitive, case could matter on the Internet some time in the future.

You can theoretically have up to 127 labels (that is, levels) in a domain name, although this would be highly impractical.

According to RFC 1034, “when assigning a domain name for an object, the prudent user will select a name which satisfies both the rules of the domain system and any existing rules for the object, whether these rules are published or implied by existing programs.”


Checking Your Network Registration

You can query your network address using the whois utility to find out if the network address is registered. For example:

whois -h rs.internic.net 192.42.95
Process Software Corporation (NET-PSC)
   959 Concord Street
   Framingham, MA 01701

Netname: PSC

   Volz,Bernard (BV15) VOLZ@PROCESS.COM
   (508) 879-6994

Domain System inverse mapping provided by:


Record last updated on Ol-Jul-94.

If you’re not registered, use anonymous FTP to access rs.intemic.net (address and copy the /template/internet-number-template.txt file for instructions.


Registering the Domain Name with Your Parent

The best way to register with your parent is to contact the domain “coordinator,” like the one listed in the previous example. There are various registration forms available, or you can send the information to the coordinator in an e-mail message.

You need to supply the names and addresses of your domain name servers. In some cases, these should already be operational.


Setting up a Reverse Mapping DOmain

You can register your reverse mapping domain names in the in-addr.arpa domain by anonymous FTP to rs.internic.net (address Follow the instructions in the /template/in-address-template.txt file.

You also have to set up information locally for reverse mapping and other information you should keep in the DNS database on your name servers. These local maintenance issues are covered in the next chapter.


Setting up a DNS Client and Servers

Each TCP/IP software product has its own way of configuring a DNS client resolver and servers. In TCPware's case, for example, your host can support a DNS client only, or both a client and a name server. The TCPware setup procedure prompts you to specify the internet addresses of up to three name servers the client can query.