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
In computer networking, a routing table, or routing information base (RIB), is a data table stored in a router or a network host that lists the routes to particular network destinations, and in some cases, metrics (distances) associated wi ...
. 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
Bandwidth commonly refers to:
* Bandwidth (signal processing) or ''analog bandwidth'', ''frequency bandwidth'', or ''radio bandwidth'', a measure of the width of a frequency range
* Bandwidth (computing), the rate of data transfer, bit rate or thr ...
,
load,
hop count
In wired computer networking a hop occurs when a packet is passed from one network segment to the next. Data packets pass through routers as they travel between source and destination. The hop count refers to the number of network devices thro ...
, path cost,
delay
Delay or DeLay may refer to:
People
* B. H. DeLay (1891–1923), American aviator and movie stunt pilot
* Dorothy DeLay (1917–2002), American violin instructor
* Florence Delay (born 1941), French academician and actor
* Jan Delay, stage name ...
,
maximum transmission unit
In computer networking, the maximum transmission unit (MTU) is the size of the largest protocol data unit (PDU) that can be communicated in a single network layer transaction. The MTU relates to, but is not identical to the maximum frame size tha ...
(MTU),
reliability
Reliability, reliable, or unreliable may refer to:
Science, technology, and mathematics Computing
* Data reliability (disambiguation), a property of some disk arrays in computer storage
* Reliability (computer networking), a category used to des ...
and communications cost.
Examples
A metric can include:
* measuring link utilization (using SNMP)
* number of hops (
hop count
In wired computer networking a hop occurs when a packet is passed from one network segment to the next. Data packets pass through routers as they travel between source and destination. The hop count refers to the number of network devices thro ...
)
* 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
Bandwidth commonly refers to:
* Bandwidth (signal processing) or ''analog bandwidth'', ''frequency bandwidth'', or ''radio bandwidth'', a measure of the width of a frequency range
* Bandwidth (computing), the rate of data transfer, bit rate or thr ...
* throughput
NMP - query routers*
load
*
maximum transmission unit
In computer networking, the maximum transmission unit (MTU) is the size of the largest protocol data unit (PDU) that can be communicated in a single network layer transaction. The MTU relates to, but is not identical to the maximum frame size tha ...
(MTU)
* administrator configured value
In
EIGRP
Enhanced Interior Gateway Routing Protocol (EIGRP) is an advanced distance-vector routing protocol that is used on a computer network for automating routing decisions and configuration. The protocol was designed by Cisco Systems as a proprietary pr ...
, metrics is represented by an integer from 0 to 4,294,967,295 (The size of a 32-bit integer). In
Microsoft Windows XP
Windows XP is a major release of Microsoft's Windows NT operating system. It was released to manufacturing on August 24, 2001, and later to retail on October 25, 2001. It is a direct successor to Windows 2000 for high-end and business users a ...
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
Administrative distance (AD) or route preference is a number of arbitrary unit assigned to dynamic routes, static routes and directly-connected routes. The value is used in routers to rank routes from most preferred (low AD value) to least pre ...
, 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