Notes
Routing metrics
Hop counts
HOP counts refer to the number of devices, usually routers, that a piece of data travels through. Each time that a packet of data moves from one router (or device) to another — say from the router of your home network to the one just outside your county line — that is considered one HOP.
MTU
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 that can be transported on the data link layer, e.g. Ethernet frame.
Larger MTU is associated with reduced overhead. Smaller MTU values can reduce network delay. In many cases, MTU is dependent on underlying network capabilities and must be adjusted manually or automatically so as to not exceed these capabilities. MTU parameters may appear in association with a communications interface or standard. Some systems may decide MTU at connect time, e.g. using Path MTU Discovery.
Bandwidth
Bandwidth is the maximum rate of data transfer across a given path.
Latency
Latency is a measure of delay. In a network, latency measures the time it takes for some data to get to its destination across the network.