|This article does not cite any references or sources. (December 2009)|
In computer networking, a network service is an application running at the network application 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 architecture based on application layer network protocols.
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 them.
|Internet protocol suite|
|The OSI model|
|7 Application layer|
|6 Presentation layer|
|5 Session layer|
|4 Transport layer|
|3 Network layer|
|2 Data link layer|
|1 Physical layer|
In computer network programming, the application layer is an abstraction layer reserved for communications protocols and methods designed for process-to-process communications across an Internet Protocol (IP) computer network. Application layer protocols use the underlying transport layer protocols to establish host-to-host connections.
TCP-IP network services
Many Internet Protocol-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.
Examples are the Domain Name System (DNS) which translates domain names to Internet protocol (IP) addresses and the Dynamic 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.
Other network services include:
- Directory services
- File sharing
- Instant messaging
- Online game
- File server
- Voice over IP
- Video on demand
- World Wide Web
- Simple Network Management Protocol
- Time service
- Wireless sensor network