Editing Network throughput (section)

==Channel utilization and efficiency==
Throughput is sometimes normalized and measured in percentage, but normalization may cause confusion regarding what the percentage is related to. ''Channel utilization'', ''channel efficiency'' and ''[[Packet loss|packet drop rate]]'' in percentage are less ambiguous terms.

The channel efficiency, also known as [[bandwidth utilization efficiency]], is the percentage of the [[net bit rate]] (in {{nowrap|bit/s}}) of a digital [[communication channel]] that goes to the actually achieved throughput. For example, if the throughput is {{nowrap|70 Mbit/s}} in a {{nowrap|100 Mbit/s}} Ethernet connection, the channel efficiency is 70%. In this example, effectively 70&nbsp;Mbit of data are transmitted every second.

Channel utilization is instead a term related to the use of the channel, disregarding the throughput. It counts not only with the data bits, but also with the overhead that makes use of the channel. The transmission overhead consists of preamble sequences, frame headers and acknowledge packets. The definitions assume a noiseless channel. Otherwise, the throughput would not be only associated with the nature (efficiency) of the protocol, but also to retransmissions resultant from the quality of the channel. In a simplistic approach, channel efficiency can be equal to channel utilization assuming that acknowledge packets are zero-length and that the communications provider will not see any bandwidth relative to retransmissions or headers. Therefore, certain texts mark a difference between channel utilization and protocol efficiency.

In a point-to-point or [[point-to-multipoint communication]] link, where only one terminal is transmitting, the maximum throughput is often equivalent to or very near the physical data rate (the [[channel capacity]]), since the channel utilization can be almost 100% in such a network, except for a small inter-frame gap.

For example, the maximum frame size in Ethernet is 1526 bytes: up to 1500 bytes for the payload, eight bytes for the preamble, 14 bytes for the header, and 4 bytes for the trailer. An additional minimum interframe gap corresponding to 12 bytes is inserted after each frame. This corresponds to a maximum channel utilization of 1526&nbsp;/ (1526&nbsp;+ 12)&nbsp;× 100%&nbsp;= 99.22%, or a maximum channel use of {{nowrap|99.22 Mbit/s}} inclusive of Ethernet datalink layer protocol overhead in a {{nowrap|100 Mbit/s}} Ethernet connection. The maximum throughput or channel efficiency is then 1500&nbsp;/ (1526&nbsp;+ 12)&nbsp;= 97.5%, exclusive of the Ethernet protocol overhead.