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Routing 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
editA 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:[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
editRouter 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 is typically based on information like path length, bandwidth, load, hop count, path cost, delay, MTU, reliability and communications cost.
See also
edit- Administrative distance, indicates the source of routing table entry and is used in preference to metrics for routing decisions[2][3][4]
References
edit- ↑ Rao, S. Dharma; Murthy, C. Siva Ram (2005). "Distributed dynamic QoS-aware routing in WDM optical networks". Computer Networks. 48 (4): 585–604. doi:10.1016/j.comnet.2004.11.003.
- ↑ "Administrative Distance and Metric". Archived from the original on 2021-11-22. Retrieved 2021-12-23.
- ↑ "Understand the significance of administrative distance and metrics when working with routers". 19 May 2005. Archived from the original on 2021-12-23. Retrieved 2021-12-23.
- ↑ "Administrative distance & metric". 26 January 2016. Archived from the original on 2021-12-23. Retrieved 2021-12-23.