Axel AX3000 65 User's Manual Manual de usuario descargar pdf (Pagina 233)

Appendix

AX3000 - User's Manual 221

A.4 - THE DNS PROTOCOL

The DNS protocol (Domain Name System) allows names to be 'resolved' by the

AX3000. Resolving is retrieving an IP address associated with a name.

A.4.1 - Overview

A domain (computer network) can be considered as a tree, with branches

(nodes) such as hubs, switches, routers, print servers etc, and leafs, for

example PCs, terminals and printers.

The domain system makes no distinction between the use of interior nodes and

the leafs, and this documentation uses the term "nodes" to refer to both. (i.e.

any network resource).

Each node has a name (Label) which must be unique to other nodes at the

same level, but not necessarily unique within the whole network.

Label syntax:

- Permissible characters are letters (a..z to A..Z), numbers (0..9) and the

hyphen (-).

- A Label must begin by a letter and be ended by a letter or a number.

- The resolution is not case-sensitive.

The domain name of a node is the list of the labels on the path from the node to

the root of the tree. A dot is used to separate each label. Two types of host

names can be distinguished within the AX3000:

- A full name: one or more dots are included in the name.

Example: "www.axel.com"

- An incomplete name: no dots are used. The resolution procedure

concatenates, another character string to this name (the default DNS

domain name). For more information see Chapter 3.1.2.

Example: "as400" is concatenated with "servers.axel.com" to create a full

name of "as400.servers.axel.com"

A host name is only resolved if the IP address is needed. (i.e. to open a session

or to ping).

Note: a name is resolved for each connection attempt, even if its IP address

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Axel AX3000 65 User's Manual Manual de usuario Pagina 233