Bay Networks NauticaRS, Справочное руководство

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NauticaRS 5.5R Reference Guide
Routing Concepts
The cost of installing and running a network to meet an
organization’s communication needs, has generally been
proportional to the distance over which the network extends, and
the range of services required.
Large amounts of data can be moved easily and relatively
inexpensively by local area networks (LANs), such as for an
office or a department, by adding more equipment, providing
network speeds of 10-100 megabits per second. However,
interconnecting local networks at similar speeds is very
expensive, due to the cost of installing the infrastructure which
can provide that level of output.
Therefore common practice is to interconnect local high-speed
networks using slower-speed links; since it is always cheaper to
install additional bandwidth in a localized area rather than over a
wide area network. Routing is the process in which traffic is sent
using the slower wide area links. This ensures maximum
throughput over the slower link.
Techniques for routing data between high-speed LANs over
slower-speed wide area networks (WANs) have evolved over the
years, and use various media protocols. The ability to uniquely
identify the source and destination of the data is critical to allow
the success of operations across the WAN link.
What Is a Router?
A router is a device designed to deliver data from the source
network to a location within the correct destination network.
Once the data has reached the correct destination network, the
router’s task is to ensure that the data reaches the correct station
on that network. Most routing environments use a network
number and a station or node number to uniquely identifying each
destination. This method is similar to the way the post office to
sends mail to your home, using different classes of location
information such as recipient name, street name and town.