Metrics (networking)

Router metrics are metrics 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.

For other uses, see Metric (disambiguation).

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)
  • latency (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:[1]

  • 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.

References
  1. S. D. Rao, C. S. R. Murthy: “Distributed dynamic QoS-aware routing in WDM optical networks”, Computer Networks, Volume 48, Issue 4, 15 July 2005, Pages 585-604
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