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
Network delay is a design and performance characteristic of a telecommunications network. It specifies the latency for a bit of data to travel across the network from one communication endpoint to another. It is typically measured in multiple ...
* path reliability
* path
bandwidth
* throughput
NMP - 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 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
References
{{reflist
External links
Survey of routing metrics
Computer network analysis
Network performance
Metrics