| Routing In Network Layer |
Routing (or routeing) is the process of selecting paths in a
network along which to send data or physical traffic. Routing is performed for
many kinds of networks, including the telephone network, the Internet, and
transport networks.
Routing directs forwarding, the passing of logically addressed packets from
their source toward their ultimate destination through intermediary nodes;
typically hardware devices called bridge routers,
gateways, firewalls, or switches. Ordinary computers with multiple network cards
can also forward packets and perform routing, though with more limited
performance. The routing process usually directs forwarding on the basis of
routing tables which maintain a record of the routes to various network
destinations. Thus constructing routing tables, which are held in the routers'
memory, becomes very important for efficient routing.
Routing, in a more narrow sense of the term, is often contrasted with
bridging in its assumption that network addresses are structured and that
similar addresses imply proximity within the network. Because structured
addresses allow a single routing table entry to represent the route to a group
of devices, structured addressing (routing, in the narrow sense) outperforms
unstructured addressing (bridging) in large networks, and has become the
dominant form of addressing on the Internet, though bridging is still widely
used, albeit within localized environments.
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