Best-effort delivery describes a

network service In computer networking, a network service is an application running at the network layer and above, that provides data storage, manipulation, presentation, communication or other capability which is often implemented using a client–server or pe ...

in which a network does not provide any guarantee that data is effectively delivered or that delivery meets any

quality of service Quality of service (QoS) is the description or measurement of the overall performance of a service, such as a telephony or computer network, or a cloud computing service, particularly the performance seen by the users of the network. To quantitat ...

. In a best-effort network, all users obtain best-effort service. Under best-effort, network performance characteristics such as transmission speed,

network delay Network delay is a design and performance characteristic of a telecommunications network. It specifies the latency for a bit of data to travel across the network from one communication endpoint to another. It is typically measured in multiple ...

and

packet loss Packet loss occurs when one or more packets of data travelling across a computer network fail to reach their destination. Packet loss is either caused by errors in data transmission, typically across wireless networks, or network congestion.Ku ...

depend on the current network traffic load, and the network hardware capacity. When network load increases, this can lead to

, retransmission,

packet delay variation In computer networking, packet delay variation (PDV) is the difference in end-to-end one-way delay between selected packets in a flow with any lost packets being ignored. The effect is sometimes referred to as packet jitter, although the de ...

, further

, or even timeout and session disconnect. Best-effort can be contrasted with reliable delivery, which can be built on top of best-effort delivery (possibly without latency and throughput guarantees), or with

virtual circuit A virtual circuit (VC) is a means of transporting data over a data network, based on packet switching and in which a connection is first established across the network between two endpoints. The network, rather than having a fixed data rate reser ...

schemes which can maintain a predefined quality of service. There are aspects of network neutrality and

fair use Fair use is a Legal doctrine, doctrine in United States law that permits limited use of copyrighted material without having to first acquire permission from the copyright holder. Fair use is one of the limitations to copyright intended to bal ...

Network examples

Physical services

The

postal service The mail or post is a system for physically transporting postcards, letters, and parcels. A postal service can be private or public, though many governments place restrictions on private systems. Since the mid-19th century, national postal sy ...

(''snail mail'') physically delivers letters using a best-effort delivery approach. The delivery of a certain letter is not scheduled in advance – no resources are preallocated in the post offices. The service will make their "best effort" to try to deliver a message, but the delivery may be delayed if too many letters suddenly arrive at a postal office or triage center. The sender is generally not informed when a letter has been delivered successfully, unless one pays for this premium service. When the addressee is unknown the message might be returned to sender. Or the letter might be definitively lost or destroyed without notification. Conventional telephone networks are not based on best-effort communication, but on

circuit switching Circuit switching is a method of implementing a telecommunications network in which two network nodes establish a dedicated communications channel ( circuit) through the network before the nodes may communicate. The circuit guarantees the full ...

. During the connection phase of a new call, resources are proactively reserved in the

telephone exchange A telephone exchange, telephone switch, or central office is a central component of a telecommunications system in the public switched telephone network (PSTN) or in large enterprises. It facilitates the establishment of communication circuits ...

s along the path, or a busy signal informs the user that the call failed due to a lack of capacity. An ongoing phone call can never be interrupted due to overloading of the network,Except by emergency calls when there are no more free channels and is guaranteed constant bandwidth (both of which are not guaranteed in a mobile telephone network).

Internet

The

Internet Protocol The Internet Protocol (IP) is the network layer communications protocol in the Internet protocol suite for relaying datagrams across network boundaries. Its routing function enables internetworking, and essentially establishes the Internet. IP ...

offers a best-effort service for delivering datagrams between hosts.

IPv4 Internet Protocol version 4 (IPv4) is the first version of the Internet Protocol (IP) as a standalone specification. It is one of the core protocols of standards-based internetworking methods in the Internet and other packet-switched networks. ...

and

IPv6 Internet Protocol version 6 (IPv6) is the most recent version of the Internet Protocol (IP), the communication protocol, communications protocol that provides an identification and location system for computers on networks and routes traffic ...

is an internet protocol that depends on the best-effort delivery approach. Datagrams may be lost, arbitrarily delayed, corrupted, or duplicated. The

User datagram protocol In computer networking, the User Datagram Protocol (UDP) is one of the core communication protocols of the Internet protocol suite used to send messages (transported as datagrams in Network packet, packets) to other hosts on an Internet Protoco ...

(UDP) provides a simple layer which only error-checks the datagrams.

Transmission control protocol The Transmission Control Protocol (TCP) is one of the main communications protocol, protocols of the Internet protocol suite. It originated in the initial network implementation in which it complemented the Internet Protocol (IP). Therefore, th ...

(TCP) provides a guaranteed delivery of an octet stream between two processes on a pair of hosts to the above layer, internally splitting the stream into packets and individually resending these when lost or corrupted. The applications built on top of those protocols implement the additional services they require on an end-to-end basis. Both transport-layers are the base protocols and provide

multiplexing In telecommunications and computer networking, multiplexing (sometimes contracted to muxing) is a method by which multiple analog or digital signals are combined into one signal over a shared medium. The aim is to share a scarce resource� ...

between processes on the same host running over different port numbers.

Ethernet

Ethernet Ethernet ( ) is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 198 ...

is an industry standard of best-effort for local networks, while synchronous ethernet allows for guaranteed delivery for high speed connections.

References

{{DEFAULTSORT:Best Effort Delivery Network performance

Network examples

Physical services

Internet

Ethernet

Further reading

References