Router metrics
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Router metrics are
metrics METRIC (Mapping EvapoTranspiration at high Resolution with Internalized Calibration) is a computer model developed by the University of Idaho, that uses Landsat satellite data to compute and map evapotranspiration (ET). METRIC calculates ET as a re ...
used by a router to make routing decisions. A ''metric'' is typically one of many fields in a
routing table In computer networking A computer network is a set of computers sharing resources located on or provided by Node (networking), network nodes. The computers use common communication protocols over digital signal, digital Interconnection, inter ...

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 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 Load or LOAD may refer to: Aeronautics and transportation *Load factor (aeronautics), the ratio of the lift of an aircraft to its weight *Passenger load factor, the ratio of revenue passenger miles to available seat miles of a particular transpor ...
,
hop count In wired computer networking A computer network is a group of computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations automatically. Modern computers can perform generic se ...
, path cost, delay,
maximum transmission unit In computer networking A computer network is a set of computers sharing resources located on or provided by Node (networking), network nodes. The computers use common communication protocols over digital signal, digital Interconnection, inter ...
(MTU),
reliability Reliability, reliable, or unreliable may refer to: Science, technology, and mathematics Computing * Data reliability (disambiguation), Data reliability, a property of some disk arrays in computer storage * High availability * Reliability (computer ...
and communications cost.


Examples

A metric can include: * measuring link utilization (using SNMP) * number of hops (
hop count In wired computer networking A computer network is a group of computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations automatically. Modern computers can perform generic se ...
) * speed of the path * packet loss (router congestion/conditions) *
Network delay Network delay is a design and performance characteristic of a telecommunications network A telecommunications network is a group of nodes In general, a node is a localized swelling (a "knot") or a point of intersection (a Vertex (graph theory), ...
* 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 Load or LOAD may refer to: Aeronautics and transportation *Load factor (aeronautics), the ratio of the lift of an aircraft to its weight *Passenger load factor, the ratio of revenue passenger miles to available seat miles of a particular transpor ...
*
Maximum transmission unit In computer networking A computer network is a set of computers sharing resources located on or provided by Node (networking), network nodes. The computers use common communication protocols over digital signal, digital Interconnection, inter ...
(MTU) * administrator configured value In
EIGRP Enhanced Interior Gateway Routing Protocol (EIGRP) is an advanced distance-vector routing protocol A distance-vector routing protocol in data networks determines the best route for data packets based on distance. Distance-vector routing protocols ...
, 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 an operating system An operating system (OS) is system software that manages computer hardware, computer software, software resources, and provides common daemon (computing), services for computer programs. Time-sharing opera ...
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 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 Router (computing), routers to rank Routing, routes from most preferred (lo ...
, indicates the source of routing table entry and is used in preference to metrics for routing decisions


References

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External links


Survey of routing metrics
Computer network analysis Network performance Metrics