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Echo LANlink Router Option User Manual Issue 1.0 04 December 1997 Page 7 of 59
The Router Option card is easily configured using the management terminal
connected to the Echo LANlink from either end of the link, or through Telnet
at a relevant workstation either LAN.
1.1 Functional Overview
The Router Option card supports both transceiver connection (AUI port) and
hub (10BASE-T port) connection to a 10MHz Ethernet LAN. Ethernet frames
are transported to/from the remote LAN using some or all of the main
communications link bandwidth. The bandwidth is allocated in 64Kbps
timeslots amongst the various functions of the multiplexer as required by the
user. Up to 1984Kbps free bandwidth is available on an E1 link, 64Kbps is
permanently assigned for E1 frame synchronisation and signalling.
The router supports both the popular Internet Protocol (IP) and Internetwork
Packet Exchange (IPX) protocols. Many other protocols may be used
encapsulated by these as required: e.g. TCP, UDP, and NetWare.
The router maintains dynamic routing tables so that Ethernet frames are
routed to their correct destination. This capability is performed automatically
by the router as it “learns” routes and addresses available in the network. The
router will also broadcast its own routing information to other devices on the
network. Inoperative routes will time-out and be removed from the routing
tables so that alternative routes may be used in the event a communications
circuit failure.
A data compression algorithm is used when transporting Ethernet frames
through the communications link to increase the throughput of data.
Comprehensive filtering options are available so the router may act as a
sophisticated firewall to give added security for the LAN.
1.2 Typical Applications
The simplest application for the Router Option is to link two LANs as shown in
Figure 1. In this example, the Branch Office is linked to the Headquarters via
the Echo LANlinks and users at the Branch office will be able to access the
General Servers as if they were on the same network.
Further use of the router functionality can give sophisticated security for
network elements. Restrictive firewalls are easily built using subnet masking.
Entire subnets can be isolated from the network by simply entering
appropriate configurations – see Figure 2. In this example the Salesperson in