Routing Protocol Algorithm

The Application of routing selection Protocol plays an important role in many large networks. In order to allow everyone to better master this part of knowledge, we have summarized the basic content of the Route Selection protocol. Including its redundancy and routing algorithm. A vro provides a way to open up a path through a mesh connection. This mesh network provides redundant paths to adjust the communication load or reverse link, there is usually a route that is preferred to other routes for reasons such as cost, speed, or avoidance of congestion, provide the router with the route information they need to establish the optimal path through the mesh network ｡

When a computer sends a group, each layer of the network protocol stack attaches some information to it. The peer layer protocol of the receiver can read this information. This information is similar to some parts of the communication session. route Selection information, this may be through the complete path of a network or some indication groups should use the priority value of that path. The network layer information added by the sender can only be read by the router or receiver's network layer protocol. the bridge cannot identify network layer information, only transfer and forwarding groups are allowed ｡

Routing Algorithms Route Selection Algorithm

A Router device may have two or more ports that can send data groups. It must have a forwarding table) specify a specific address for each port. In the early days, the router did not exchange information about the router with other routers. Therefore, a router usually sends data groups along each path, and the group is full of networks, in addition, some groups sent are continuously circulating on the network ｡

To avoid these problems, the router can rely on manual programming to input the selected path into the device. This is called static routing selection. dynamic routing is a better way, it relies on routers to collect network information and establish their own route tables. Routers exchange route tables with each other and combine these route information to create an updated route table. Information obtained from other routers, provides the number of Route Relay (hop) or route-related fees for the destination site on the network. At the same time, select the route table on the device for each route, it should contain roughly the same routing selection information. In the wide area network using the Remote Communication Link, regular routing selection is basic, but must be rapidly changed on the remote communication link (for example, Line Disconnection) A typical Internet may consist of 2, 10, or even 50 routers, these routers can connect to each other through a dial-up asynchronous link or a dedicated high-speed digital line (such as T1). For a Data Group transmitted over the network, when they arrive at the vro, The vro can view the destination address, and send the group to the receiving station along the best or very suitable route. Such a route depends on the routing algorithm type used. There are basically two types of routing selection protocols: distance vector and link status, the two protocols are described in the following two paragraphs ｡

Distance Vector routing selection Protocol

The packet transfer route of the Distance Vector routing selection protocol is determined based on the number of hops to the receiving station or the cost, this information is provided by neighboring routers. Technically, it follows the Bellman-Ford algorithm. A router has several ports and each port has a specified value, these values are set by the network administrator. The actual cost of using a line is measured as a way to indicate that one line is better or worse than the other, the neighboring routers tell them the cost of sending the group to the destination site. The router adds the value of the port to the value of the neighboring router, as shown in the following example: port 1 Value: 10 + neighboring routers value: 17 = 27. Port 2 value: 20 + neighboring routers value: 5 = 25. Port 3 value: 30 + neighboring routers value: 7 = 37. In this case, the router transmits the Group through Port 2 because it indicates that the cost to the receiving station is the least. If necessary, the value of the route to the next vro is calculated using the vro of the adjacent Port 2 ｡

Next hop address

The value measure is the value used to select a path when the router forwards the route to the next vro in the forward packet to the next vro in the network. The common distance vector routing selection protocols include: Route Selection Information Protocol (RIP) is a distance vector routing protocol first implemented in Xerox Network System (XNS) and then implemented in Novell's NetWare) is the distance vector routing protocol developed by Cisco. The route selection table maintenance protocol (RTMP) is an Apple protocol that selects the best path in two AppleTalk zones and broadcasts it every 10 seconds ｡

Distance Vector routing is not suitable for large networks with hundreds of routers or frequently-updated networks. In large networks, the table update process may be too long, so that the selection table of the farthest router is unlikely to be updated synchronously with other tables. In this case, the selection of link status routes is more desirable, the Link Status Protocol can isolate confidential information in special areas for security purposes, or avoid crowded areas such as computer-aided design (CAD) and multimedia communication, the routing information table is exchanged instead of regularly when necessary, which can reduce information traffic on the network ｡

Link Status routing selection Protocol

Link Status routing requires stronger processing capability than distance vector routing, however, it can provide more control over the routing selection process and provide faster response to changes. The routing can be based on avoiding congestion areas, line speeds, line costs, or various priority levels. Dijkstra Algorithm used for route computing, the number of routers that the Group sends to the destination station is as follows: Route Relay (hop). The smaller the number of hops, the better ｡