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To illustrate the operation of a dial-up remote bridge, Fig. 1 shows two sites, each
with a backbone FDDI network linking 100VG-AnyLAN hubs.
Users connected to end nodes 1 and 2 want to communicate by video and audio
between the two sites. The backbone networks on each site are connected to the
wide area network (WAN) through dial-up remote bridges specifically designed to
carry multimedia traffic. We assume that site A and site B can also communicate
through existing routes, such as some kind of corporate internet.
When the call between node 1 and node 2 is initialized, an isochronous link with
the appropriate bit rate is set up between the two dial-up bridges. Bridge A is told
the 48-bit MAC address of node 2. Any subsequent packets that appear on the
backbone FDDI bearing that destination address will be forwarded across the
WAN. Bridge B puts them on the backbone FDDI at site B, from which they reach
node 2.
Any normal-priority data packets destined for node 2 will not be picked up by
bridge A because they will carry the destination address of the router connecting
site A to the corporate internet, not that of node 2.
Site A
Site B
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Fig. 1. Remote sites connected by dial-up remote bridges.
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