metrics (networking)
{{Short description|Field in a routing table used to make routing decisions}}
{{other uses|Metric (disambiguation)}}
{{Refimprove|date=January 2009}}
{{Use American English|date=June 2020}}
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
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:{{cite journal | doi=10.1016/j.comnet.2004.11.003 | title=Distributed dynamic QoS-aware routing in WDM optical networks | year=2005 | last1=Rao | first1=S. Dharma | last2=Murthy | first2=C. Siva Ram | journal=Computer Networks | volume=48 | issue=4 | pages=585–604 }}
- 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 is typically based on information like path length, bandwidth, load, hop count, path cost, delay, MTU, reliability and communications cost.
See also
- Administrative distance, indicates the source of routing table entry and is used in preference to metrics for routing decisions{{cite web |title=Administrative Distance and Metric |url=https://etutorials.org/Networking/Integrated+cisco+and+unix+network+architectures/Chapter+8.+Static+Routing+Concepts/Administrative+Distance+and+Metric/ |access-date=2021-12-23 |archive-date=2021-11-22 |archive-url=https://web.archive.org/web/20211122173400/http://etutorials.org/Networking/Integrated+cisco+and+unix+network+architectures/Chapter+8.+Static+Routing+Concepts/Administrative+Distance+and+Metric/ |url-status=live }}{{cite web |title=Understand the significance of administrative distance and metrics when working with routers |date=19 May 2005 |url=https://www.techrepublic.com/article/understand-the-significance-of-administrative-distance-and-metrics-when-working-with-routers/ |access-date=2021-12-23 |archive-date=2021-12-23 |archive-url=https://web.archive.org/web/20211223222331/https://www.techrepublic.com/article/understand-the-significance-of-administrative-distance-and-metrics-when-working-with-routers/ |url-status=live }}{{cite web |title=Administrative distance & metric |date=26 January 2016 |url=https://study-ccna.com/administrative-distance-metric/ |access-date=2021-12-23 |archive-date=2021-12-23 |archive-url=https://web.archive.org/web/20211223222332/https://study-ccna.com/administrative-distance-metric/ |url-status=live }}
References
{{reflist}}
External links
- [http://rainer.baumann.info/public/tik262.pdf Survey of routing metrics]