In computer networking, anetwork 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 aclient–server orpeer-to-peer architecture based on application layernetwork protocols.[1]
Each service is usually provided by aserver 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 auser interface, and sometimes other hardware associated with it.
Examples are the Domain Name System (DNS) which translates domain names toInternet Protocol (IP) addresses and theDynamic Host Configuration Protocol (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,printing anddistributed (network) file system services are common services onlocal area networks. They require users to have permissions to access the shared resources.
Other network services include:
| Internet protocol suite |
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| Application layer |
| Transport layer |
| Internet layer |
| Link layer |
| OSI model bylayer |
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Incomputer network programming, theapplication layer is anabstraction layer reserved forcommunications protocols and methods designed for process-to-process communications across anIP network. Application layer protocols use the underlyingtransport layer protocols to establish host-to-host connections for network services.
Many IP-based services are associated with a particularwell-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.
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-innetwork congestion avoidance and the protocols that use it must be extremely carefully designed to prevent network collapse.
Network Service – a capability that facilitates a network operation. It typically is provided by a server (which can be running one or more services), based on network protocols running at the application layer in the Open Systems Interconnection (OSI) model of the network.