How Do I Choose the Best DVR?

The key to the quality of routing is the routing algorithm. There are many kinds of routing algorithms, which can be roughly divided into two categories: static algorithms and dynamic algorithms. ^[1]

Static routing algorithm refers to the pre-calculation of each router using some routing algorithm.

The network topology and traffic volume change dynamically, such as routers joining or exiting, and network congestion or congestion. If the router can obtain these dynamic changes of the network in time and use this as the basis for routing, it will help the router optimize the routing. The dynamic routing algorithm uses this mechanism for routing. It is also called adaptive routing algorithm.

Modern computer network systems usually use dynamic routing algorithms. Among the dynamic routing algorithms, distance vector routing and link state routing are the two most commonly used algorithms.

After the router is started, it immediately establishes a routing relationship with its neighboring routing device. The purpose of this initial communication is to identify neighboring devices, start communication and learn the network structure. The method of establishing the adjacency relationship and the initial learning of the topology structure vary with the choice of the routing protocol.

The routing protocol periodically exchanges HELLO messages or routing update packets to maintain reachability between neighboring devices. An ideal routing algorithm should have the following characteristics:

(1) The routing algorithm must be correct and complete. A data packet can guide the data packet to the final destination network and destination host according to the routing table generated by the routing algorithm.

(2) Simplicity. The routing algorithm should be simple in calculation when generating the routing table, and should not add too much extra overhead to the network traffic.

(3) Adaptability. The routing algorithm can dynamically change routes based on the current network status and network traffic to balance the load on each link of the network. That is, when a certain node or link of the network fails to work normally, or when it is repaired and put into operation, the algorithm can change the route in time.

(4) Stability. When the network traffic and network topology are relatively stable, the routing algorithm should converge to an acceptable solution, and the routing should not be constantly changed.

(5) Fairness. The routing algorithm is equal for all users.

(6) Optimality. Optimality refers to implementing routing algorithms at the lowest cost. The cost here refers to the metric (Metric) determined by one or several comprehensive factors, such as link length, data rate, link capacity, propagation delay, and so on. Therefore, the optimality here can only be a reasonable choice based on a specific requirement. ^[2]