Common Metrics in Communication
Metrics is a property of a route in computer networking, consisting of any value used by routing algorithms to determine whether one route should perform better than another (the route with the lowest metric is the preferred route). The routing table stores only the best possible routes, while link-state or topological databases may store all other information as well. For example,Routing Information Protocol uses hopcount (number of hops) to determine the best possible route.
A Metric can include:
- measuring link utilisation (using SNMP)
- number of hops (hop count)
- speed of the path
- packet loss (router congestion/conditions)
- latency (delay)
- path reliability
- path bandwidth
- throughput [SNMP - query routers]
- maximum transmission unit (MTU)
In EIGRP, metrics is represented by an integer from 0 to 4294967295. 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.