Metrics (networking)
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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
[edit]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:[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
[edit]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 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.