Metrics (networking)

Router metrics are configuration values used by a router to make routing decisions. A metric is typically one of many fields in a routing table. Router metrics help the router choose the best route among multiple feasible routes to a destination. The route will go in the direction of the gateway with the lowest metric.

A router metric is typically based on information such as path length, bandwidth, load, hop count, path cost, delay, maximum transmission unit (MTU), reliability and communications cost.

Examples
A metric can include:
 * measuring link utilization (using SNMP)
 * number of hops (hop count)
 * speed of the path
 * packet loss (router congestion/conditions)
 * Network delay
 * path reliability
 * path bandwidth
 * throughput [SNMP - query routers]
 * load
 * Maximum transmission unit (MTU)
 * administrator configured value

In EIGRP, metrics is represented by an integer from 0 to 4,294,967,295 (The size of a 32-bit integer). In Microsoft Windows XP routing it ranges from 1 to 9999.

A metric can be considered as:
 * additive - the total cost of a path is the sum of the costs of individual links along the path,
 * concave - the total cost of a path is the minimum of the costs of individual links along the path,
 * multiplicative - the total cost of a path is the product of the costs of individual links along the path.

Service level metrics
Router metrics are metrics used by a router to make routing decisions. It is typically one of many fields in a routing table.

Router metrics can contain any number of values that help the router determine the best route among multiple routes to a destination. A router metric typically based on information like path length, bandwidth, load, hop count, path cost, delay, MTU, reliability and communications cost.