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Chapter 1. Understanding SDSL and the Express L768
61203192L1-20 Express L768 User Manual 1-5
The Express L768 provides the following basic functions:
1. LAN Bridge: Bridging provides a point-to-point connection
between two LANs. The bridge learning function scans the
source and destination media access control (MAC) addresses of
all packets on its local LAN and determines which packets
should be transmitted over the SDSL link. Applications include
connectivity between single user or small offices to corporate
LANs. The Express L768 uses the Spanning Tree Algorithm
(IEEE 802.1d-ISO/IEC10038), which provides a loop-free
topology and redundancy.
2. IP Router: The Express L768 can function as an IP router using
the Routing Information Protocol (RIP) for advertising and learn-
ing routes among other routers. Static routes may also be entered
into the routing table.
3. IPX Router: IPX routers and services can be exchanged between
the Express L768 and other devices using RIP and Service Adver-
tising Protocol (SAP). Watch dog serialization filtering and spoof-
ing can permit the ISDN to be idle during no application traffic
periods.
4. Network Address Translation (NAT): Single networks can con-
nect to the Internet with this function. The Express L768 trans-
lates outgoing IP packets over the SDSL to the IP router at the
Internet Service Provider. Many popular Internet applications
are supported.
5. PPP or Frame Relay: The layer two protocol used to transfer
packets can be PPP or Frame Relay (RFC 1490). PPP allows a
point-to-point connection, whereas Frame Relay can provide up
to ten permanent virtual circuits.