A Link-state routing is a concept used in routing of packet-switched networks in computer communications. Link-state routing works by having the routers tell every router on the network about its closest neighbors. The entire routing table is not distributed from any router, only the part of the table containing its neighbors. The following are some key characters of the Link-state routing concept:

1. The neighbor information is gathered continuously.
2. The neighbor information list is then broadcasted to every router that can answer to this protocol, a process known as flooding, which means that it sends the information to all of its neighbors who in turn send it to all of their neighbors and so on. Soon, all routers on the network have this information.
3. The neighbor information is flooded whenever there is a (routing-significant) change in the network.
4. As every router knows everything about the network by structuring the information from other routers, it can calculate the best path to any host on any destination network.

Some of the link-state routing protocols are the OSPF, IS-is and EIGRP. Novell's NLSP (NetWare Link State Protocol) is also a link-state routing protocol, which only supports IPX. This type of routing protocol requires each router to maintain at least a partial map of the network. When a network link changes state (up to down, or vice versa), a notification, called a link state advertisement (LSA) is flooded throughout the network. All the routers note the change, and re-compute their routes accordingly.

LinkState Routing protocols provide greater flexibility and sophistication than the Distance Vector routing protocols. They reduce overall broadcast traffic and make better decisions about routing by taking characteristics such as bandwidth, delay, reliability, and load into consideration, instead of basing their decisions solely on distance or hop count.

MajorLinkState Routing Protocols Characteristics

Related Terms: OSPF, IS-IS, EIGRP, NLSP, Distance Vector Routing Protocol