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

peer-to-peer Peer-to-peer (P2P) computing or networking is a distributed application architecture that partitions tasks or workloads between peers. Peers are equally privileged, equipotent participants in the network, forming a peer-to-peer network of Node ...

architecture based on application layer

network protocols A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any variation of a physical quantity. The protocol defines the rules, syntax, semantics, and synchronization of ...

. Each service is usually provided by a server component running on one or more computers (often a dedicated server computer offering multiple services) and accessed via a network by client components running on other devices. However, the client and server components can both be run on the same machine. Clients and servers will often have a user interface, and sometimes other hardware associated with it.

Examples

Examples are the Domain Name System (DNS) which translates domain names to

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 ...

(IP) addresses and the

Dynamic Host Configuration Protocol The Dynamic Host Configuration Protocol (DHCP) is a network protocol, network management protocol used on Internet Protocol (IP) networks for automatically assigning IP addresses and other communication parameters to devices connected to the netw ...

(DHCP) to assign networking configuration information to network hosts. Authentication servers identify and authenticate users, provide user account profiles, and may log usage statistics.

Email Electronic mail (usually shortened to email; alternatively hyphenated e-mail) is a method of transmitting and receiving Digital media, digital messages using electronics, electronic devices over a computer network. It was conceived in the ...

printing Printing is a process for mass reproducing text and images using a master form or template. The earliest non-paper products involving printing include cylinder seals and objects such as the Cyrus Cylinder and the Cylinders of Nabonidus. The ...

and distributed (network) file system services are common services on

local area network A local area network (LAN) is a computer network that interconnects computers within a limited area such as a residence, campus, or building, and has its network equipment and interconnects locally managed. LANs facilitate the distribution of da ...

s. They require users to have permissions to access the shared resources. Other network services include: *

Directory services In computing, a directory service or name service maps the names of network resources to their respective network addresses. It is a shared information infrastructure for locating, managing, administering and organizing everyday items and network ...

File sharing File sharing is the practice of distributing or providing access to digital media, such as computer programs, multimedia (audio, images and video), documents or electronic books. Common methods of storage, transmission and dispersion include ...

Instant messaging Instant messaging (IM) technology is a type of synchronous computer-mediated communication involving the immediate ( real-time) transmission of messages between two or more parties over the Internet or another computer network. Originally involv ...

Online game An online game is a video game that is either partially or primarily played through the Internet or any other computer network available. Online games are ubiquitous on modern gaming platforms, including PCs, consoles and mobile devices, a ...

Printing Printing is a process for mass reproducing text and images using a master form or template. The earliest non-paper products involving printing include cylinder seals and objects such as the Cyrus Cylinder and the Cylinders of Nabonidus. The ...

File server In computing, a file server (or fileserver) is a computer attached to a network that provides a location for shared disk access, i.e. storage of computer files (such as text, image, sound, video) that can be accessed by workstations within a co ...

Voice over IP Voice over Internet Protocol (VoIP), also known as IP telephony, is a set of technologies used primarily for voice communication sessions over Internet Protocol (IP) networks, such as the Internet. VoIP enables voice calls to be transmitted as ...

Video on demand Video on demand (VOD) is a media distribution system that allows users to access videos, television shows and films Digital distribution, digitally on request. These multimedia are accessed without a traditional video playback device and a typica ...

Videotelephony Videotelephony (also known as videoconferencing or video calling) is the use of audio signal, audio and video for simultaneous two-way communication. Today, videotelephony is widespread. There are many terms to refer to videotelephony. ''Vide ...

World Wide Web The World Wide Web (WWW or simply the Web) is an information system that enables Content (media), content sharing over the Internet through user-friendly ways meant to appeal to users beyond Information technology, IT specialists and hobbyis ...

Simple Network Management Protocol Simple Network Management Protocol (SNMP) is an Internet Standard protocol for collecting and organizing information about managed devices on IP networks and for modifying that information to change device behavior. Devices that typically su ...

* Time service *

Wireless sensor network Wireless sensor networks (WSNs) refer to networks of spatially dispersed and dedicated sensors that monitor and record the physical conditions of the environment and forward the collected data to a central location. WSNs can measure environmental ...

Application layer

computer network programming Computer network programming involves writing computer programs that enable processes to communicate with each other across a computer network. Connection-oriented and connectionless communications Very generally, most of communications c ...

, the

application layer An application layer is an abstraction layer that specifies the shared communication protocols and interface methods used by hosts in a communications network. An ''application layer'' abstraction is specified in both the Internet Protocol Su ...

is an

abstraction layer In computing, an abstraction layer or abstraction level is a way of hiding the working details of a subsystem. Examples of software models that use layers of abstraction include the OSI model for network protocols, OpenGL, and other graphics libra ...

reserved for

communications protocol A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any variation of a physical quantity. The protocol defines the rules, syntax, semantics (computer science), sem ...

s and methods designed for process-to-process communications across an

IP network The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the suite are ...

. Application layer protocols use the underlying

transport layer In computer networking, the transport layer is a conceptual division of methods in the layered architecture of protocols in the network stack in the Internet protocol suite and the OSI model. The protocols of this layer provide end-to-end c ...

protocols to establish host-to-host connections for network services.

TCP-IP network services

Port numbers

Many IP-based services are associated with a particular well-known port number which is standardized by the Internet technical governance. For example, World-Wide-Web servers operate on port 80, and email relay servers usually listen on port 25.

TCP versus UDP

Different services use different packet transmission techniques. In general, packets that must get through in the correct order, without loss, use TCP, whereas real time services where later packets are more important than older packets use UDP. For example, file transfer requires complete accuracy and so is normally done using TCP, and audio conferencing is frequently done via UDP, where momentary glitches may not be noticed. UDP lacks built-in

network congestion Network congestion in data networking and queueing theory is the reduced quality of service that occurs when a network node or link is carrying more data than it can handle. Typical effects include queueing delay, packet loss or the blocking of ...

avoidance and the protocols that use it must be extremely carefully designed to prevent network collapse.

References