Describes the application of the Route Selection protocol.

At present, the routing selection protocol is widely used. We believe that with the development of the communication industry, the routing selection protocol will be more stable and improved, bringing users a good network environment. When two non-directly connected computers need to communicate over several networks, a router is usually required.

A vro provides a way to open up a path through a mesh connection. The figure R-9 shows several paths that exist in offices in Los Angeles and New York. This kind of mesh network provides redundant paths to adjust the communication load or inverted link. There is usually a path that is preferred to other paths for reasons such as cost, speed, or avoidance of congestion. The task of routing selection Protocol is to provide the router with the route information they need to establish the optimal path through the mesh network.

When a computer sends a group, some information is appended to each layer of the network protocol stack on the network. This information can be read from the peer layer protocol of the receiver. This information is similar to some parts of a communication session. The Network Layer Protocol append route selection information, which may be through the complete path of a network or some indicate that the group should adopt the priority value of that path. The network layer information added by the sender can only be read by the network layer protocol of the router or receiver. The repeater and bridge cannot identify network-layer information and can only transmit and forward group information.

Routing Algorithms Route Selection Algorithm

A Router device may have two or more ports that can send data packets. It must have a forwarding table) to indicate a specific address for each port. In the early days, routers do not exchange information about routers with other routers. Therefore, a vro sends data groups along each path, and the groups are 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 to the device. This is called static routing. Dynamic routing is a better way. It relies on routers to collect network information and build their own route tables. Routers exchange route tables with each other and combine these route information to create an updated route table. The number of Route relay hops or the cost related to the routes obtained from other routers to the destination sites on the network. At the same time, the route table on each route selection device should contain roughly consistent route selection information. In the wide area network using the Remote Communication Link, regular routing is basic, but the remote communication link must rapidly change, for example, Line Disconnection, quickly adjust to the new path topology. A typical Internet may consist of 2, 10, or even 50 routers. These routers can connect to each other through a dialing 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 most suitable route. Such a route depends on the algorithm type of the route used. There are basically two types of routing protocols: distance vector and link status. The two types of protocols are described in the following two sections.

Distance Vector routing selection Protocol

The packet transfer route of the Distance Vector routing protocol is determined by the number of hops to the receiving station or the cost. The information is provided by the neighboring routers. Technically, the Bellman-Ford algorithm is followed. A Router R-10) has several ports, each of which has the specified value set by the network administrator. The actual cost of one line is used as a measure to indicate that one line is better or worse than the other. In addition, neighboring routers tell them the cost of sending the group to the destination site. The vro adds the value of the port to the value of the adjacent vro. The value of Port 1 is 10 + that of the adjacent vro is 17 = 27. Port 2 is worth 20 + neighboring routers 5 = 25. Port 3 value: 30 + value of neighboring routers 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, calculate the value of the path to the next vro with the vro2 of the adjacent Port 2.

Next hop address

Value measurement is the value used to select a path when the router forwards the packet to the next vro in the network. General distance vector routing selection protocols include: routing selection Information Protocol (RIP), which is first implemented in Xerox Network System (XNS, then the distance vector routing protocol is implemented in Novell's NetWare. IGRP is a distance vector routing protocol developed by Cisco. Route Selection table maintenance protocol (RTMP) is an Apple protocol that selects the best path in two AppleTalk zones. It is broadcast every 10 seconds.

Distance Vector routing is not suitable for large or frequently updated networks with hundreds of routers. In a large network, 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, you can select the link status route. In addition, the link status protocol can isolate confidential information in special areas for security reasons, or avoid crowded areas such as computer-aided design CAD on the Internet) and multimedia communication. In addition, the routing selection information table performs exchange when necessary, instead of regular exchange, which can reduce information traffic on the network.

Link Status routing selection Protocol

Link Status routing requires stronger processing capability than distance vector routing, but it can provide more control over the routing selection process and provide faster response to changes. Routing selection can be based on avoiding congestion areas, line speed, line costs or various priority levels. The Dijkstra algorithm is used to calculate the route. The number of routers that pass through the group to the destination station is called route relay hop. The smaller the number of hops, the better.