Digi PortServer II, User Manual

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90030500B Introduction Page 7
SLIP and CSLIP
SLIP (Serial Line Interface Protocol) or CSLIP (Compressed Serial Line Interface
Protocol) can be used with older systems that do not support PPP.
Filters and scripts
Filters can be used with PPP, SLIP, and CSLIP connections to bring up or maintain a
connection, to pass or block packets, or to log packets. For example, you can write a
filter that will block all incoming packets, except those to a certain IP address, and so
build a “firewall”. Other filters block selected packets, for example, to block out
broadcast messages. Filters are typically used to control access to specific hosts, net-
works or services, and thus increase security on your system. If PortServer II detects
packets that are blocked by a filter, it drops the packets.
Scripts are used to establish outgoing connections by dialing modems and logging in
to remote systems. They can also be used to initialize and test modems. A typical
script initializes the local modem, then a second script sends a text string to log in to
the remote location. It then waits for a predefined reply string to be received from the
remote site before it establishes the connection.
RADIUS
PortServer II supports the RADIUS (Remote Authentication Dial In Service) standard
for authentication of dial-up users. A RADIUS server receives user connection
requests, authenticates the user against a password file or database, and returns
sufficient configuration information to allow the service to be initiated. If RADIUS is
used on a connection, the RADIUS server is responsible for all authentication, and
PortServer II only routes messages and responses.
Frame Relay
Frame Relay is a switched digital service available from many providers that permits
several virtual connections to share a single physical connection. Each virtual
connection is referred to as a PVC (Permanent Virtual Connection) and corresponds to
a link between two points on the network; part of that link (the physical connection)
may be shared by other users. The maximum speed of the link is determined by the
bandwidth of the physical connection.
Note: Frame Relay also allows the use of SVCs (Switched Virtual Circuits). SVCs
are not supported by PortServer II.