Compatible Systems 5.4 Manuale Utente

If remote node operation is desired, the WAN interface would usually be set 
up as an unnumbered interface, and the Remote Node Address would then be 
set to an unused IP address from the router’s Ethernet network(s).

Alternatively, if the interface is set to be numbered, an unused address from 
the interface’s host range may be used.

As always, it is imperative in either case that this IP address be unique.

The address should be entered as four decimal numbers separated by periods 
-- for example 198.238.10.10

Named for the gentleman who developed it, VJHC (Van Jacobson Header 
Compression) is a standard method of reducing the amount of redundant IP 
header information which is transferred over a wide area connection. VJHC 
reduces the size of the IP header to as few as three bytes.

There is a trade-off between the amount of time it takes to compress the 
header information, and the amount of time it would take to simply send it in 
native form across the WAN link.

v Note:  A general rule of thumb for Compatible Systems routers would be to 
use VJHC on uncompressed links at up to 56K rates, but to turn it off at higher 
speeds or if other means of compression (such as the V.42 compression built 
into modems) are in use. A few simple file copy transfer tests over your partic-
ular WAN setup will yield a more exact answer.

A few third party routers implement the PPP specification in such a way that 
they require a PPP Address Configure Request to be sent when IP communi-
cations are being negotiated. This checkbox tells the router to include such a 
request with the IP address for this interface. Most routers do not require this 
information, and this checkbox should generally be left unchecked (default 
value).