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Fig. 2.5 Port configurations for X.25 network lines (PADconfiguration questions are shown in lower case and the responses of the site manager in upper case)

A popular option is to configure terminal characteristics in a Profile,
so that the PAD has knowledge of all possible hardware that may connect
to a user port. The Profile can then be named when configuring ports,
thus easing the task of repeating the same description for many ports.
Also, the user can adopt a new Profile very easily if a different terminal is
to be connected to a port. By giving a command such as Profile ABX3,
all the characteristics of the ABX3 terminal are loaded into the X.3
parameters without the need to give individual X.28 commands for every
parameter.

The X.28 Profile command performs this function but also sets the
X.3 parameters relevant to the host as well.

2.4.2 Address configuration

The X.28 commands provide the ability for a user to make a call out
onto the network by giving the address to which a connection is required.
We saw in Chapter 1 that the address is conceptually like a telephone
number, and that it may be 15 digits long.

One of the useful features that a PAD may have is a mnemonic address
mechanism that allows keywords to be used instead of the actual address.
Thus if the PAD has been configured with the knowledge that
WORDPROC is at address 5813421764791 then the users of the PAD
can use the command:

CA WORDPROC
instead of CA 5813421764791

Such a feature makes the PAD non-compliant with X.28.

It is necessary for a definite command to be used to make the call
when using mnemonic addresses, otherwise there could be confusion
over whether a mnemonic address or a command was being given. This
clearly makes life easier for the users. There are a number of mechanisms
to implement this, but essentially they all rely on a table, and may be
configured as shown in Fig. 2.6.

There are some problem areas with this type of scheme. Firstly, there
needs to be a known search order of mnemonic addresses in the table: is
it alphabetic, is it by length, or is the search order configured by the site
manager when the table is created? Secondly, there has to be a known

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