| The network address helps the router identify a path
within the network cloud. The router uses the network address to identify the destination
network of a packet within an internetwork. In addition to the
network address, network protocols use some form of host, or node, address.
For some network layer protocols, a network administrator assigns
network host addresses according to some predetermined internetwork
addressing plan. For other network layer protocols, assigning host
addresses is partially or completely dynamic/automatic. The graphic
shows three devices in Network 1 (two workstations and a router), each with its own unique
host address. (it also shows that the router is connected to two other networks - Networks
2 & 3).
Addressing occurs at the network layer. Earlier analogies
of a network address include the first portions (area code and first three digits) of a
telephone number. The remaining (last four) digits of a phone number tell the phone company equipment which specific phone to ring. This is similar to the function of the host portion of an address. The host portion tells the router to which specific device it should deliver a packet.
Without network layer addressing, routing can not take
place. Routers require network addresses to ensure proper delivery of packets. Without
some hierarchical addressing structure, packets would not be able to travel across an
internetwork. In a similar
way, without some hierarchical structure to telephone numbers, postal
addresses, or transportation systems, there would not be a smooth
delivery of the goods and services.
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