When taking various protocol overheads into account, the useful rate of the data transfer can be significantly lower than the maximum achievable throughput; the useful part is usually referred to as goodput.
In most cases, the benchmark of what a system is capable of, or its maximum performance is what the user or designer is interested in.
Four different values are relevant in the context of maximum throughput are used in comparing the upper limit conceptual performance of multiple systems.
Data compression can significantly alter throughput calculations, including generating values exceeding 100% in some cases.
In some cases, this number is reported as equal to the channel capacity, though this can be deceptive, as only non-packetized systems technologies can achieve this.
Maximum theoretical throughput is more accurately reported taking into account format and specification overhead with best-case assumptions.
The asymptotic throughput (less formal asymptotic bandwidth) for a packet-mode communication network is the value of the maximum throughput function, when the incoming network load approaches infinity, either due to a message size,[3] or the number of data sources.
Asymptotic throughput is usually estimated by sending or simulating a very large message (sequence of data packets) through the network, using a greedy source and no flow control mechanism (i.e., UDP rather than TCP), and measuring the network path throughput in the destination node.
Alternatively, a large number of sources and sinks may be modeled, with or without flow control, and the aggregate maximum network throughput measured (the sum of traffic reaching its destinations).
This value can also be used deceptively in relation to peak measured throughput to conceal packet shaping.
The transmission overhead consists of preamble sequences, frame headers and acknowledge packets.
Some of these are described below: The maximum achievable throughput (the channel capacity) is affected by the bandwidth in hertz and signal-to-noise ratio of the analog physical medium.
Despite the conceptual simplicity of digital information, all electrical signals traveling over wires are analog.
The analog limitations of wires or wireless systems inevitably provide an upper bound on the amount of information that can be sent.
For example, a gateway router supporting a populated class B subnet, handling 10 × 100 Mbit/s Ethernet channels, must examine 16 bits of address to determine the destination port for each packet.
In a worst-case scenario, where the payloads of each Ethernet packet are reduced to 100 bytes, this number of operations per second jumps to 520 billion.
If a bottleneck communication link offering data rate R is shared by "N" active users (with at least one data packet in queue), every user typically achieves a throughput of approximately R/N, if fair queuing best-effort communication is assumed.
The maximum throughput is often an unreliable measurement of perceived bandwidth, for example the file transmission data rate in bits per seconds.
To determine the actual data rate of a network or connection, the "goodput" measurement definition may be used.
Because the units of throughput are the reciprocal of the unit for propagation delay, which is 'seconds per message' or 'seconds per output', throughput can be used to relate a computational device performing a dedicated function such as an ASIC or embedded processor to a communications channel, simplifying system analysis.
Throughput over analog channels is defined entirely by the modulation scheme, the signal-to-noise ratio, and the available bandwidth.