Comprehensive Analysis of router introduction, working methods and protocols

Routing Algorithm

The routing algorithm plays a vital role in the routing protocol. The algorithm used often determines the final routing result. Therefore, you must carefully select the routing algorithm. The following design goals are usually taken into account:

1) Optimization: the routing algorithm's ability to select the optimal path.

2) conciseness: The algorithm design is concise, and the most effective functions are provided with the least software and overhead.

3) Robustness: the routing algorithm runs correctly when it is in an abnormal or unpredictable environment, such as hardware failure, overload, or operation error. BecauseVroDistributed on the network connection point, so they will have serious consequences in case of faults. The best router algorithms are often time-tested and proven to be reliable in various network environments.

4) fast convergence: convergence is the process in which all routers reach the same path. When a network event causes a route to be available or unavailable, the router sends an update message. The route update information is distributed throughout the network, causing re-calculation of the Optimal Path to eventually reach the best path recognized by all routers. Slow convergence routing algorithms may cause path loops or network interruptions.

5) Flexibility: routing algorithms can quickly and accurately adapt to various network environments. For example, if a CIDR Block fails, the routing algorithm must quickly discover the fault and select another optimal path for all routes using the CIDR block.

Routing Algorithms can be divided into the following types: static and dynamic, single and multi-path, equality and classification, source routing and transparent routing, intra-domain and Inter-Domain, link status and distance vector. The preceding features are basically the same as the literal meanings. Next we will introduce the link status and distance vector algorithms.

The link status algorithm, also known as the shortest path algorithm, sends route information to all nodes on the Internet. However, for each router, only the part of its own link status is described in the routing table that sends it. Distance vector algorithms, also known as the Bellman-Ford algorithm, require each router to send all or part of its route table information, but only to neighboring nodes. Essentially, the link status algorithm sends a small amount of update information to all parts of the network, while the Distance Vector Algorithm sends a large amount of update information to the adjacent router.

Because the link state algorithm converges faster, it is more difficult to generate a route loop than the distance vector algorithm to a certain extent. On the other hand, the link state algorithm requires higher CPU capability and more memory space than the distance vector algorithm, so the link state algorithm will be more expensive to implement. In addition to these differences, the two algorithms can run well in most environments.

It should be pointed out that the routing algorithm uses many different measurement standards to determine the optimal path. Complex routing algorithms may use multiple metrics to select routes. They are combined into a single composite metric and then entered into the routing table as the routing standard through a certain weighting operation. The commonly used measurements include path length, reliability, latency, bandwidth, load, and communication cost.

Next-generation Router

Due to the development of multimedia and other applications in the network, and the continuous adoption of new technologies such as ATM and fast Ethernet, the bandwidth and speed of the network are rapidly increased, traditional routers cannot meet the performance requirements of routers. Because the design and implementation of group forwarding of traditional routers are based on software, grouping processing takes many steps during the forwarding process, and the forwarding process is complicated, making the forwarding rate slow. In addition, as a key device for network interconnection and a "Gateway" for network communication with other networks, vrouters have high security requirements, therefore, the additional security measures in the vro increase the CPU burden, which makes the vro a "bottleneck" on the Internet ".

A traditional Router performs a series of complex operations when forwarding each group, including route search, access control table matching, address resolution, priority management, and other additional operations. These operations greatly affect the performance and efficiency of the router, reduce the packet forwarding rate and forwarding throughput, and increase the CPU burden. Vro groups are highly correlated. groups with the same destination address and source address often arrive consecutively, which provides the possibility and basis for fast forwarding. New-generation routers, such as IP switches and Tag switches, use this design idea to implement fast forwarding using hardware, which greatly improves the performance and efficiency of routers.

The next-generation router uses the forwarding cache to simplify group forwarding. In the process of fast forwarding, you only need to perform traditional route forwarding for the first several groups with the same destination address and source address, the destination address, source address, and next vro address of the successfully forwarded group are stored in the forwarding cache. When the next group is to be forwarded, Yin first checks the forwarding cache. If the destination address and Source Address of the group match the forwarding cache, forwarding is directly based on the next gateway address in the forwarding cache, without the need for traditional complex operations, which greatly reduces the burden on the router and improves the router throughput.

For more information about vro, see:

Comprehensive Analysis of router introduction, working methods and protocols

The router introduction, working method, and Protocol