Basic routing algorithm design goals and types

The goal and type of the basic routing algorithm design. We hope you can learn about the basic routing algorithm. First, the specific target of the algorithm designer affects the operation of the routing protocol. Secondly, there are multiple routing algorithms, each of which has different effects on the network and router resources. Finally, the routing algorithm uses a variety of metric, which affects the calculation of the optimal path. The following sections analyze the features of these routing algorithms.

1. Basic routing algorithm design objectives

The basic routing algorithm generally has one or more of the following design goals:
◆ Optimization
◆ Simple and low consumption
◆ Robust and stable
◆ Quick Aggregation
◆ Flexibility

Optimization refers to the ability of the basic routing algorithm to select the optimal path, which is calculated based on the value and weight of metric. For example, a routing algorithm may use hops and latency, but the delay may have a higher weight. Of course, the routing protocol must strictly define the metric algorithm.

 

Basic routing knowledge Routing Algorithm

The basic routing algorithm can also be designed as simple as possible. In other words, the routing protocol must provide its functions efficiently to minimize the overhead of software and applications. This is especially important when the software that implements routing algorithms must run on computers with limited physical resources.

Basic routing algorithms must be robust, that is, they must still be able to handle abnormal or unforeseen events, such as hardware faults, high loads, and incorrect implementations. Because the routers are located at the network connection points, a major problem occurs when they fail. The best routing algorithms are usually those that have been tested by time and proved to be stable under various network conditions.

In addition, the basic routing algorithm must be able to be quickly aggregated. Aggregation is the process in which all routers agree on the optimal path. When a network event causes a path to be disconnected or unavailable, the router distributes route update information through the network, promotes the calculation of the optimal path, and finally makes an agreement between all routers. Slow aggregation of routing algorithms may cause routing loops or network interruptions.

In the routing ring, a group reaches vro1 1 at the time t1, vro1 1 has been updated, and the optimal route to reach the destination is vro2 2 as the next hop, then, the group is forwarded to vro2 2. However, vro2 2 has not been updated. It considers the next hop as vro1 1, so it sends the group back to vro1 1, the result group is transmitted back and forth between the two routers until vro2 2 receives the route update information or the group exceeds the lifetime.

The basic routing algorithms should also be flexible, that is, they should quickly and accurately adapt to various network environments. For example, if a CIDR block is disconnected, many routing algorithms will quickly select the second best path for the path that uses the CIDR block after the problem is identified. The routing algorithm can be designed to adapt to network bandwidth, router queue size, and network latency.

2. Basic routing algorithm types

The differences between different routing algorithms include:
◆ Static and dynamic
◆ Single path and multi-path
◆ Flat and layered
◆ Host intelligence and router intelligence
◆ Intra-domain and Inter-Domain
◆ Link status and Distance Vector

(1) Static and Dynamic

The Static Routing Algorithm is difficult to calculate as an algorithm. It is only a table ing established by the network administrator before the routing starts. These mappings do not change unless the network administrator changes them. Static Routing Algorithms are easy to design and work well in predictable and simple network communication. Because the Static Routing System does not reflect network changes, it is generally considered not applicable to the current large and variable network.

In 1990s, the main routing algorithms were dynamic routing algorithms. They analyzed the received route update information to adapt to the changes in the network environment. If the information indicates that the network has changed, the routing software recalculates the route and sends new route update information. This information is infiltrated into the network, prompting the router to recalculate and change the route table accordingly. Dynamic Routing Algorithms can be supplemented by Static Routing where appropriate. For example, the last available route router of last resort) is used as the path for all non-route groups, ensuring that all data can be processed in at least one way.

(2) single path and multi-path

Some complex routing protocols support multiple routes to the same destination. Unlike basic single-path routing algorithms, these multi-path algorithms allow data to be reused on multiple lines. The advantages of multi-path algorithms are obvious: they provide better throughput and reliability.

(3) flattening and layering

Some routing protocols operate in a flat space, while others have routing layers. In a flat routing system, each router is equivalent to all other routers. In a hierarchical routing system, some routers constitute the routing trunk, and data flows from the non-trunk router to the trunk router, transmit the data on the trunk until they reach the destination region. Here, the data is transmitted from the last trunk router to the destination through one or more non-trunk routers.

A routing system is usually designed with a logical node group called a domain, autonomous system, or interval. In a layered system, some routers can communicate with vrouters in other domains, while others can only communicate with vrouters in the same region. In a large network, there may be other levels. The most advanced router forms the routing trunk.

The main advantage of hierarchical routing is that it simulates the structure of most companies and can support communication well. Most network communication occurs in the group domain ). Because the routers in the domain only need to know other routers in the domain, their routing algorithms can be simplified. According to the routing algorithms used, the traffic for route update can be reduced accordingly.

(4) host intelligence and router intelligence

Some routing algorithms assume that the source node determines the entire path, which is usually called the source route. In the source routing system, a vro acts only as a storage and forwarding device and unconsciously sends a next hop to the group. Other routing algorithms assume that the host has no knowledge about the path. In these algorithms, the router decides the path through the network based on its own computing. In the previous system, the host has the intelligence that determines the route, and the latter has this capability for the router.

The compromise between host intelligence and router intelligence is actually the best balance between routing and additional overhead. Generally, the host intelligent system can select a better path because it explores all possible paths before sending data, and then selects the optimal path based on the system's definition of "optimization. However, determining the behavior of all paths usually requires a lot of exploration traffic and a long time.

(5) Intra-domain and Inter-Domain

Some routing algorithms work only in the domain, while others work both in the domain and between domains. These two algorithms are essentially different. The reason is that the optimized intra-Domain Routing Algorithm does not need to be an optimized Inter-Domain Routing Algorithm.

(6) Link Status and Distance Vector

The link status algorithm is also called the short path Priority Algorithm). Route information is distributed to each node of the network. However, each router sends only the section in the routing table describing its own link status. The distance vector algorithm is also called the Bellman-Ford algorithm). Each router sends all or part of the route table, but only sends it to its neighbors. That is to say, the link status algorithm sends less update information everywhere, while the distance vector algorithm only sends more update information to adjacent routers.

Because the link state algorithms aggregate quickly, they tend to generate routing loops less than distance algorithms. On the other hand, the link status algorithm requires more CPU and memory resources, so the implementation and support of The Link Status algorithm is expensive. Although there are differences, these two algorithm types can work well in most environments.

3. metric of the basic routing algorithm

The routing table contains information that is used by the exchange software to select the optimal path. But how is a route table created? What is the essence of information they contain? How does the routing algorithm determine which path is better based on the information? The routing algorithm uses many different metric to determine the optimal path. Complex routing algorithms can select routes based on multiple metric and combine them into a composite metric. The commonly used metric is as follows:
◆ Path length
◆ Reliability
◆ Latency
◆ Bandwidth
◆ Load
◆ Communication cost

The path length is the most common route metric. Some routing protocols allow the network administrator to manually assign value to each network link. In this case, the route length is the total cost of each link. Other Routing Protocols define the number of hops, that is, the number of network products that a group must pass through from the source to the destination, such as the number of routers.

Reliability: In the basic routing algorithm, the network link dependency is usually described by the bit error rate). Some network links may be more invalid than others. After the network fails, some network connections may be easier or faster to fix than others. Any reliability factor can be taken into consideration when assigning a value to the Failover rate. Generally, the network administrator assigns a metric value to the network link.

Route delay refers to the time taken by the group to arrive at the destination from the source over the network. Many factors affect latency, including the bandwidth of intermediate network connections, the port queues of Each router, The Congestion Degree of all intermediate network connections, and the physical distance. Because latency is a mixture of multiple important variables, it is a common and effective metric.

Bandwidth refers to the available circulation capacity of the link. When all other conditions are equal, 10 Mbps Ethernet connections are more desirable than 64 Kbps leased lines. Although the bandwidth is the maximum throughput that a link can obtain, it is not necessarily better to route through a link with a large bandwidth than a slow link. For example, if a fast link is busy, it may take longer for the Group to reach the destination.

Load refers to the amount of network resources, such as the number of busy vrouters. Load can be calculated in many ways, including CPU usage and the number of processing groups per second. It is resource-consuming to continuously monitor these parameters. The communication cost is another important metric. In particular, some companies may be more cost-effective than performance. Even if the line latency may be long, they would rather send data over their own lines than using expensive public lines.