Operation Manual

Leased Lines
NT/MPRI – 4 Special NT/MPRI Settings 64
The SAP (Service Advertising Protocol) is used by servers to advertise
their services and addresses in a network. Filtering SAP packets can re-
strict access to certain services such as printers or file servers. If some
of the SAP packets arriving at the router from the LAN can be discarded
(by the SAP input filter), then the information in the router’s SAP table
can be reduced to the bare essentials.
Every incoming and outgoing RIP/SAP packet is checked by the
RIP/SAP filters for a matching filter rule.
The following filters exist:
l RIP input filter: a filter for incoming RIP packets (from the LAN or a
call destination to the router).
l RIP output filter: a filter for outgoing RIP packets (from the router
to the LAN or a remote call destination).
l SAP input filter: a filter for incoming SAP packets (from the LAN or
a call destination to the router).
l SAP output filter: a filter for outgoing SAP packets (from the router
to the LAN or to a call destination).
4.2 Leased Lines
Two different kinds of leased lines can be configured to work with the
NT/MPRI:
1. Static leased line
On this kind of leased line, connections are established using a
specified number of B channels. It is not possible to add B chan-
nels. The number of B channels is defined in the configuration of
the leased line.
2. Dynamic leased line
On this kind of leased line, additional B channels can be added
dynamically depending on the load transmitted over the connec-
tion. The B channels are added in the form of dial-up connections.
In both cases, the configuration of a leased line requires both settings
on the ISDN adapter and a new call destination setup.
The next two sections describe the configuration of both of these types
of leased lines.
ntmpri-e.book Seite 64 Donnerstag, 28. Februar 2002 11:26 11