Route

Routing information is passed from the source to the destination through the network behavior, at least in the propagation path through an intermediate node.
Routing is usually to compare with the bridge, in the careless person, that they seem to done the same thing. The main difference is that bridging occurs in the second layer of OSI reference model (data link layer), and routing in the third layer (network layer). The difference between the two in the process of transmission of information using different information to different ways to accomplish their tasks.
Route has long been the subject appears in the computer industry, but until the mid-eighties a commercial success. The main reason is the network of the seventies in general is very simple to the later development of large-scale network to be more common.
Routing of work consists of two basic actions: 1, to determine the best path
2, transmission of information through the network
In the routing process, which is also known as the (data) exchange. Exchange is relatively simple, the choice of the path is very complicated.
1, path selection
metric is the routing algorithm to determine the best path to reach the destination of measurement standards, such as path length. To help routing, routing algorithms initialize and maintain routing table contains the path information, path routing algorithm based on the use of information varies.
 Routing algorithm based on a lot of information to populate the routing table. Purpose / next hop address for the purpose of this router is the best way to reach the packet sent to the representative of the "next hop" router, when a router receives a packet, it checks the destination address, try this address with "under hop "linked. Routing table can also include other information. Comparison of the routing table to determine the best path metric, the metric used by the routing algorithm based on the difference. Routers communicate with each other through the exchange of routing information to maintain its routing table, routing updates usually contain all or part of the routing table, by analyzing routing updates from other routers of information, the router can create a network topology. The other routers send link state information is broadcast information, it notifies the sender's link to other routers status, link information is used to establish a complete topology map, so that routers can determine the best path.
2, the exchange algorithm
Exchange algorithm relatively simple for most routing protocols are the same terms, in most cases, the decision of a host to another host to send data, obtained through some router address, the source host sends point to the router Physical (MAC) address of the packet, the protocol address is a pointer to the destination host.
Routers see the purpose of the packet protocol address, know how to determine whether to forward the packet forwarding if the routers do not know how often will the discarded. If the router knows how to forward, put the purpose of the physical address into the physical address of the next hop to the transmission. Next hop may be the ultimate destination host, if not, usually another router, it will perform the same steps. When the packet flows in the network, its physical address changed, but its protocol address remains unchanged.
ISO defines the process used to describe a hierarchical terms. In this term, there is no ability to forward packets of network equipment called ES - end system, they are able, called the IS - intermediate system. IS can be further divided into intradomain IS routing domain and can communicate in the routing domain are inter-domain communication in the interdomain IS. Routing domain is generally considered part of the network under unified management, compliance with a specific set of rules, also known as autonomous system. In some protocols, routing protocols can still be used within the interval and the interval between the exchange of data.