What Is a Metric in Routing?

What Is a Metric in Routing?

Metrics help dynamic routing protocols choose the best route to a destination network. Metrics are calculated based on a number of variables including path load, reliability, speed and packet delay.

The metric that uses packet delay averaged over a ten second interval performs effec- tively under light to moderate loading, but it creates routing instabilities and wastes link and processor bandwidth for routing updates. This prompted the development of successor metrics that focus on different criteria.


In network routing, distance is one of the factors used by a router to determine which path to use for sending data packets to a destination. Each possible path to the destination is assigned a value by the routing protocol which ranks them from most preferred to least preferred. The route with the lowest metric is chosen as the optimal path and installed in the router’s routing table. This allows for dynamic routing protocols to be self-healing; if a link fails on the preferred path, traffic will be sent to the alternative path with the next lowest metric.


Throughput is a metric in routing used to measure how quickly data moves from one point to another on a network. It is a key indicator of a network’s performance and efficiency. Throughput is also related to bandwidth, which defines the maximum data transfer rate that a system can handle under ideal conditions. While both throughput and bandwidth are important metrics to track, they serve different purposes and are used in different contexts.

Bandwidth is often used as a proxy for internet speed. A higher bandwidth allows more data to be transmitted over a network connection in a given period of time, which results in faster file downloads and smoother video streaming. However, bandwidth is a theoretical limit that can be limited by various factors, such as delay (jitter) and network congestion.


Routers use routing metrics to determine the best path for network communications. They use these metrics to calculate the shortest path between a source network and a destination network. Different routing protocols represent this information in various ways. For example, RIP uses hop count, which is the number of routers through which data must pass to reach a destination network. This information is stored in a routing table, which routers use to select the best path for packets.

Metrics help dynamic routing protocols like RIP, OSPF and EIGRP decide which routes are preferred over other routes. The lowest metric in routing value is usually the best path, but there are other factors to consider as well. For example, if a route passes through a high latency link, it may not be as good as a route that uses a shorter distance.


Reliability is a term used to describe the consistency or repeatability of measurements. It is an important measurement criterion, as it indicates whether a system or process is functioning properly and will continue to do so. It can also help identify problems, such as excessive packet loss, that negatively impact the reliability of a network.

A reliable system is one that functions without failure for long periods of time. It also operates in a consistent manner under various conditions. It is similar to quality, but differs in that quality measures a static situation, while reliability measures a dynamic situation.



In this paper, a heuristic-based method is proposed for selecting multipath routing sets based on reliability classes. The technique extends Shortest Multipath Routing methods to incorporate link reliability into their cost function. The heuristic algorithm finds a cost-effective solution for the multipath routing set of each TT flow. The results show that this approach improves schedulability and reliability for industrial applications.

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