Table of contents
1. The Interaction of Routing and Forwarding
Second, the basic concept of routing
4. Classification of Routing Algorithms
4. Distributed routing algorithm
1. The Interaction of Routing and Forwarding
Second, the basic concept of routing
1. Default router
Default router: The router directly connected to the host, also known as the first-hop router. Whenever a host sends a packet, it is first sent to its default router.
- Source Router: The default router of the source host.
- Destination router: The default router of the destination host.
The route selection from the source host to the destination host boils down to the route selection from the source router to the destination router.
2. Routing algorithm
Routing Algorithm: It is an algorithm that determines the path that a packet takes from the source router to the destination router.
The key of the routing algorithm is to find the best path from the source router to the destination router in a given set of routers and the links connecting the routers.
3. Abstract model of network
1. Node graph
2. Cost
The larger the weight of the edge, the higher the link cost of the link, which means the hotter the chicken.
4. Classification of Routing Algorithms
1. Static routing algorithm
Static routing algorithm: After the route is determined, it will basically not change, and there may be some changes only when manual intervention is adjusted.
2. Dynamic routing algorithm
- Paths may change when the traffic load or topology of the network changes.
- Can respond periodically or directly to topology or link cost changes.
- Susceptible to problems such as routing loops and routing flapping.
Both the global routing algorithm and the distributed routing algorithm belong to the dynamic routing algorithm.
3. Global routing algorithm
Global routing algorithm: All routers have complete network topology information and link cost information.
Link State Routing Algorithm LS: The cost of each link in the network must be known.
4. Distributed routing algorithm
Distributed routing algorithm: Calculate the lowest cost path in an iterative and distributed manner. By iterative calculation and exchanging information with adjacent nodes, the lowest cost path to a destination node or a group of destination nodes is gradually calculated.
A node only needs to have the cost information of the links directly connected to it, and does not need to have complete information about the cost of all network links.
Distance Vector Routing Algorithm DV: Each node maintains an estimated vector of costs (distances) to all other nodes in the network.