I. Route chart
1. The route list only specifies the next step in the path from the router to the destination without knowing the complete path to the destination, the standard ip route chart contains many serials, n indicates the ip address of the destination network, and r indicates the ip address of the next router on the n path。
2. To extract the purpose ip address d from datagram, calculate the network number n, if n is directly connected to the router, elseif routingtable contains the route to n, then sends datagram to the next stop specified in routingtable, else path selection error。
3. Static routers are built and managed manually and do not automatically change, and must be manually updated to reflect changes in the structure or connection of the internet. The advantage is that it is safe and secure, simple intuitive and avoids the cost of dynamic route choice. The disadvantage is that it does not apply to complex internet structures, which create and maintain heavy workloads and are prone to routering。
3. Dynamic routing can be automatically modified and updated through self-learning. Dynamic routers require constant exchange of route information between routers. The advantage is greater autonomy and flexibility. The disadvantage is that the exchange route information requires the use of network bandwidth, that dynamic modification and updating of the route chart requires the occupancy of the router memory and cpu processing time, and that the router resources are consumed。
Ii. A routing agreement
1. Basic conditions for the use of dynamic routing, the router runs the same route selection protocol and performs the same route selection algorithm。
2. Broadly used route selection protocols, route information protocols, rips: open minimum path priority agreements, using vector-distance algorithms, osfs: using link-state algorithms。
3. Routes are condensed, and all routers on the internet operate the same route information that is precise enough to reflect the current structure of the internet, and fast-moving is the most desirable feature of route selection protocols。
Iii. Route selection algorithm
1. Vector-range route selection algorithms whereby routers regularly broadcast their own known route information to their adjacent routers to inform the adjacent routers of the network they can reach and the distance to which they can reach. The adjacent routers can modify and update their own route sheets based on the route information received. The advantage is that algorithms are simple and easy to achieve. The disadvantage is slow harvest, and the path change of the router needs to be transmitted from the adjacent router like a wave
Link-state route selection algorithms, each router on the internet regularly broadcasts its connection with the adjacent router to other routers, and each router on the internet uses the route information received to draw a map of the structure of the internet. Calculates the shortest path to each network using the drawings of an extended structure and the shortest path priority algorithm。
Vector-range route selection algorithms do not require routers to understand the entire internet pivot structure; an adjacent router is used to understand the possible path to each network, and the chain-state route selection algorithm relies on the internet-wide scale-up structure; and the entire internet scale-up structure is used to obtain spf trees, which in turn generate a route chart from spf trees。
