# Goodput > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Goodput > Markdown URL: https://mediated.wiki/source/Goodput.md > Source: https://en.wikipedia.org/wiki/Goodput > Source revision: 1353817876 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) Application-level throughput of a network This article includes a list of general references, but it lacks sufficient corresponding inline citations. Please help to improve this article by introducing more precise citations. (April 2016) (Learn how and when to remove this message) In computer networks, **goodput** (a [portmanteau](/source/Portmanteau) of *good* and *[throughput](/source/Throughput)*) is the [application-level](/source/Application_layer) throughput of a communication. In other words, goodput is the number of useful information [bits](/source/Bit) delivered by the network to a certain destination per unit of time.[1] The amount of data considered excludes [protocol overhead](/source/Protocol_overhead) bits as well as retransmitted data packets.[1] This is related to the amount of time from the first bit of the first packet sent (or delivered) until the last bit of the last packet is delivered. For example, if a file is transferred, the goodput that the user experiences corresponds to the file size in bits divided by the file transfer time. The goodput is always lower than the throughput (the gross bit rate that is transferred physically), which generally is lower than network access connection speed (the [channel capacity](/source/Channel_capacity) or [bandwidth](/source/Bandwidth_(computing))). Examples of factors that cause lower goodput than throughput include: - *Protocol overhead*: Typically, transport layer, network layer and sometimes [data link layer](/source/Data_link_layer) protocol overhead is included in the throughput, but is excluded from the goodput. - *Transport layer [flow control](/source/Flow_control_(data)) and [congestion avoidance](/source/Congestion_avoidance)*: For example, TCP slow start may cause a lower goodput than the maximum throughput. - Retransmission of lost or corrupt packets due to transport layer [automatic repeat request](/source/Automatic_repeat_request) (ARQ), caused by bit errors or [packet dropping](/source/Packet_dropping) in congested switches and routers, is included in the data link layer or network layer throughput but not in the goodput. ## Example For an application using the common [Transmission Control Protocol](/source/Transmission_Control_Protocol) (TCP) over [IPv4](/source/IPv4) over [Ethernet](/source/Ethernet), the minimum protocol overhead consists of - Ethernet physical layer: 20 bytes preamble, start frame delimiter and [interpacket gap](/source/Interpacket_gap) - Ethernet data link layer: 18 bytes [frame headers](/source/Ethernet_frame#Structure) and [frame check sequence](/source/Frame_check_sequence) - IPv4 network layer: 20 bytes [packet headers](/source/IPv4#Packet_structure) - TCP transport layer: 20 bytes [segment headers](/source/Transmission_Control_Protocol#TCP_segment_structure) for a total of 78 bytes: 38 bytes for Ethernet, and 40 bytes for IPv4 and TCP. An IP packet over Ethernet may have a size of up to 1500 bytes – the *[maximum transmission unit](/source/Maximum_transmission_unit)* for Ethernet. That means that a TCP segment can transport up 1500 - 40 = 1460 bytes, while Ethernet needs to transport 1500 + 38 = 1538 bytes. The overall efficiency is 1460 / 1538 = 94.9%. Accordingly, the maximum goodput for any application running over [100 Mbit/s Ethernet](/source/Fast_Ethernet) with TCP/IP is 94.9 Mbit/s or 11.9 [MB/s](/source/Megabytes_per_second). For [Gigabit Ethernet](/source/Gigabit_Ethernet), the same calculation results in 949 Mbit/s, or 119 MB/s. When large objects or files ([megabytes](/source/Megabyte)) are transmitted, the overhead of the application itself may be ignored since most protocols only add a single header of limited size for each object or file. When only small objects are transmitted, the overhead increases in proportion and becomes more significant. ## Data delivery time The goodput is a ratio between delivered amount of information, and the total delivery time. This delivery time includes: - Inter-packet time gaps caused by packet generation processing time (a source that does not use the full network capacity), or by protocol timing (for example [collision avoidance](/source/Collision_avoidance_(networking))) - Data and overhead [transmission delay](/source/Transmission_delay) (amount of data divided by [bit rate](/source/Bit_rate)) - [Propagation delay](/source/Propagation_delay) (distance divided by wave propagation speed) - Packet [queuing delay](/source/Queuing_delay) - [NAT](/source/Network_address_translation) translation delay - Intermediate node [store-and-forward processing delay](/source/Store_and_forward_delay) - Packet retransmission time (in case of deleted packets in congested routers, or detected bit errors) - Delayed acknowledge due to flow control, congestion avoidance and [processing delay](/source/Processing_delay) ## See also - [Measuring network throughput](/source/Measuring_network_throughput) - [Spectral efficiency](/source/Spectral_efficiency) ## References 1. ^ [***a***](#cite_ref-RFC_2647_s3.17_1-0) [***b***](#cite_ref-RFC_2647_s3.17_1-1) [*RFC 2647*](https://www.rfc-editor.org/rfc/rfc2647#section-3.17). [IETF](/source/Internet_Engineering_Task_Force). sec. 3.17. [doi](/source/Doi_(identifier)):[10.17487/RFC2647](https://doi.org/10.17487%2FRFC2647). ## Sources - [Energy-Efficient Power and Rate Control with QoS Constraints: A Game-Theoretic Approach](https://arxiv.org/abs/cs.IT/0604082) --- Adapted from the Wikipedia article [Goodput](https://en.wikipedia.org/wiki/Goodput) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Goodput?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.