Cabletron Systems Netlink FRX4000 User Manual - page 133

Configuring X.25

8-27

original subscriber cannot be reached. (See "

Redirect on Busy

" and "

Redirect on Out of 

Order

.")

The FRX4000/6000 will call each address in the list until one is reached. If 

Systematic 

Redirection

 is enabled, the FRX4000/6000 will not call the original called subscriber, 

but will start immediately with the first subscriber in the redirection list.

Configuring X.25 Address Translation Templates

The X.25 address translation function in the FRX4000/6000 provides automatic trans-

lation of selected fields within a Call Request packet, according to a previously 

defined "template." You can change the called address, calling address, user data, and/

or facilities fields of a Call Request packet as it passes into or out of the node.

There are various uses for this feature; for example:

●

For security reasons, a translation of the calling address might enable routing of 

all Call Request packets with certain addresses, while all others are cleared.

●

Translation of user data can allow rerouting of all packets with the same called 

address, with all those containing one type of information going to one location, 

while those with another type go elsewhere.

The translation template has two parts: the template ID and the translation formula. 

The Call Request packet can be modified (using the translation formula) to replace 

parts of it with characters specified by the formula and/or with parts of the template 

ID.

Each port has two sets of translation templates associated with it, one for incoming 

packets and one for outgoing packets. When an incoming packet enters the node, it is 

immediately checked against any incoming template defined for that port. If the 

packet matches the template, a translation is carried out and the packet continues 

toward its destination, using the routing tables defined by SVC Subscriber configu-

ration. If the packet does not match the template, it is not accepted.

An outgoing packet is checked just before it leaves the node. If it matches the tem-

plate, a translation is carried out; if it does not match, it continues unchanged.

The hunt group function is performed within the routing table process, so to handle 

outbound packets, a port that is part of a hunt group needs a set of templates that is 

specific to that port. This allows a different set of outbound translations for each port.

Address translation is especially useful in providing backup routing via a public data 

network (PDN), as represented in the following example.