Host (network)

<h2 id="origins">Origins</h2>
<p>In <a href="/facts/Operating_systems/8XTuvMh2">operating systems</a>, the term <i>terminal host</i> denotes a <a href="/facts/Time-sharing/LE5XT9Go">time-sharing</a> computer or <a href="/facts/Multi-user_software/XeKcRNjA">multi-user software</a> providing services to <a href="/facts/Computer_terminal/fSlx05qV">computer terminals</a>, or a computer that provides services to smaller or less capable devices,<a class="footnote-ref" id="fnref:1" href="#fn:1"><sup>1</sup></a> such as a <a href="/facts/Mainframe_computer/nrBR6rWa">mainframe computer</a> serving <a href="/facts/Teletype/pn5SQKTf">teletype</a> terminals or video terminals. Other examples of this architecture include a <a href="/facts/Telnet/hxT0e85h">telnet</a> host connected to a telnet server and an <a href="/facts/Xhost/tvWgbzlQ">xhost</a> connected to an <a href="/facts/X_Window_System/ac2vRIQL">X Window client</a>.
</p><p>The term <i>Internet host</i> or just <i>host</i> is used in a number of <a href="/facts/Request_for_Comments/esftTvE7">Request for Comments</a> (RFC) documents that define the Internet and its predecessor, the <a href="/facts/ARPANET/LyMGWurJ">ARPANET</a>. RFC 871 defines a host as a general-purpose computer system connected to a communications network for "... the purpose of achieving resource sharing amongst the participating operating systems..."<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a>
</p><p>While the ARPANET was being developed, computers connected to the network were typically mainframe computer systems that could be accessed from <a href="/facts/Dumb_terminal/fSlx05qV">dumb terminals</a> connected via <a href="/facts/Serial_port/VpcrH530">serial ports</a>. Since these terminals did not host software or perform computations themselves, they were not considered <i>hosts</i> as they were not connected to any <a href="/facts/IP_network/KNkxtSpw">IP network</a>, and were not assigned IP addresses. User computers connected to the ARPANET at a <a href="/facts/Packet-switching_node/SeXJ6CjU">packet-switching node</a> were considered hosts.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a>
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<h2 id="nodes-hosts-and-servers">Nodes, hosts, and servers</h2>
<p>A <a href="/facts/Network_node/LBp2vNcJ">network node</a> is any device participating in a network. A host is a node that participates in user applications, either as a server, client, or both. A <a href="/facts/Server_(computing)/dEaYFD7r">server</a> is a type of host that offers resources to the other hosts. Typically a server accepts connections from <a href="/facts/Client_(computing)/u0wlVsWI">clients</a> who request a service function.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a>
</p><p>Every network host is a node, but not every network node is a host. <a href="/facts/Networking_hardware/ck0rIkXA">Network infrastructure hardware</a>, such as <a href="/facts/Modem/9H0Xwtq0">modems</a>, <a href="/facts/Ethernet_hub/t90w5XMX">Ethernet hubs</a>, and <a href="/facts/Network_switch/CnvmhNYT">network switches</a> are not directly or actively participating in application-level functions, and do not necessarily have a network address, and are not considered to be network hosts.
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<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/Communication_endpoint/BSG7lnw4">Communication endpoint</a> – Type of communication network node</li>
<li><a href="/facts/End_system/Xft2yBHz">End system</a> – Computer connected to a network</li>
<li><a href="/facts/Port_(computer_networking)/ygoHVKNC">Port (computer networking)</a> – Communications endpoint in an operating system</li>
<li><a href="/facts/Terminal_(telecommunication)/GTHNGWI5">Terminal (telecommunication)</a> – Device which ends a telecommunications link</li></ul>

<h2 id="external-links">External links</h2>
<ul><li>R. Braden, ed. (October 1989). <a href="https://datatracker.ietf.org/doc/html/rfc1122"><i>Requirements for Internet Hosts -- Communication Layers</i></a>. <a href="/facts/Doi_(identifier)/muM9Etpq">doi</a>:<a href="https://doi.org/10.17487%2FRFC1122">10.17487/RFC1122</a>. <a href="/facts/Request_for_Comments/esftTvE7">RFC</a> <a href="https://datatracker.ietf.org/doc/html/rfc1122">1122</a>.</li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>E. Garrison Walters (2001). The essential guide to computing]. Prentice Hall PTR. p. 149. ISBN 9780130194695. <a href="9780130194695" target="_blank">9780130194695</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>M.A. Padlipsky (September 1982). A Perspective on the ARPANET Reference Model. doi:10.17487/RFC0871. RFC 871. <a href="https://datatracker.ietf.org/doc/html/rfc871" target="_blank">https://datatracker.ietf.org/doc/html/rfc871</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
<li id="fn:3"><p>Douglas E. Comer (2000). Internetworking with TCP/IP - Principles, Protocols and Architecture (4th ed.). Prentice Hall. p. 39. ISBN 0-13-018380-6. <a href="0-13-018380-6" target="_blank">0-13-018380-6</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li>
<li id="fn:4"><p>"Exchange Server architecture". <a href="https://docs.microsoft.com/en-us/exchange/architecture/architecture#ClientAccessProtocol" target="_blank">https://docs.microsoft.com/en-us/exchange/architecture/architecture#ClientAccessProtocol</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li>
</ol>

Host (network) open-in-new

Host (network)