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Network segment
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<h2 id="ethernet">Ethernet</h2> <p>According to the defining <a href="/facts/IEEE_802.3/Q9jxNSNT">IEEE 802.3</a> standards for <a href="/facts/Ethernet/nMfhU8tU">Ethernet</a>, a network segment is an <i>electrical connection</i> between networked devices using a <a href="/facts/Shared_medium/7BPrQ65Q">shared medium</a>.<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a> In the original <a href="/facts/10BASE5/vxgB15fH">10BASE5</a> and <a href="/facts/10BASE2/FfgUgSUz">10BASE2</a> Ethernet varieties, a segment would therefore correspond to a single coax cable and all devices tapped into it. At this point in the evolution of Ethernet, multiple network segments could be connected with <a href="/facts/Repeater/JTkWvTEP">repeaters</a> (in accordance with the <a href="/facts/5-4-3_rule/WS5Ix1GU">5-4-3 rule</a> for 10 Mbit Ethernet) to form a larger <a href="/facts/Collision_domain/xQ9ll4JE">collision domain</a>. </p><p>With <a href="/facts/Twisted-pair_Ethernet/2jRlgJb4">twisted-pair Ethernet</a>, electrical segments can be joined together using repeaters or <a href="/facts/Repeater_hub/t90w5XMX">repeater hubs</a> as can other varieties of Ethernet. This corresponds to the extent of an <a href="/facts/OSI_layer_1/WuATCrVw">OSI layer 1</a> network and is equivalent to the collision domain.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a><a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> The 5-4-3 rule applies to this collision domain. </p><p>Using <a href="/facts/Network_switch/CnvmhNYT">switches</a> or <a href="/facts/Network_bridge/5nyTQtNW">bridges</a>, multiple layer-1 segments can be combined to a common <a href="/facts/Layer-2/K9yPufbt">layer-2</a> segment, i.e. all <a href="/facts/Node_(networking)/LBp2vNcJ">nodes</a> can communicate with each other through <a href="/facts/MAC_address/SVcTfgUH">MAC addressing</a> or <a href="/facts/Broadcasting_(networking)/NRj7gHre">broadcasts</a>. A layer-2 segment is equivalent to a <a href="/facts/Broadcast_domain/yIC9czJ6">broadcast domain</a>. Traffic within a layer-2 segment can be separated into virtually distinct partitions by using <a href="/facts/VLAN/QhdJNaWX">VLANs</a>. Each VLAN forms its own logical layer-2 segment. </p> <h2 id="ip">IP</h2> <p>A <a href="/facts/Layer-3/L2jAtJzQ">layer-3</a> segment in an <a href="/facts/IP_network/KNkxtSpw">IP network</a> is called a <a href="/facts/Subnetwork/s1rQsNDv">subnetwork</a>, formed by all nodes sharing the same network prefix as defined by their IP addresses and the network mask.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> Communication between layer-3 subnets requires a <a href="/facts/Router_(computing)/Nh5cIyVf">router</a>. Hosts on a subnet communicate directly using the layer-2 segment that connects them. Most often a subnetwork corresponds exactly with the underlying layer-2 segment but it is also possible to run multiple subnets on a single layer-2 segment. </p> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>"Network Segment Definition". 2 October 2005. Retrieved 3 September 2010. <a href="http://www.linfo.org/network_segment.html" target="_blank">http://www.linfo.org/network_segment.html</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>"1.4.318", 802.3-2008 Part 3: Carrier sense multiple access with Collision Detection (CSMA/CD) Access Method and Physical Layer Specifications, IEEE, 26 December 2008, segment: The medium connection, including connectors, between Medium Dependent Interfaces (MDIs) in a CSMA/CD local area network. <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>"Segment (Network)". Retrieved 3 September 2010. <a href="http://www.linktionary.com/s/segment.html" target="_blank">http://www.linktionary.com/s/segment.html</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>"Segment". Retrieved 3 September 2010. <a href="http://compnetworking.about.com/od/networkdesign/l/bldef_segment.htm" target="_blank">http://compnetworking.about.com/od/networkdesign/l/bldef_segment.htm</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>"What is a Network Segment?". Retrieved 3 September 2010. <a href="http://www.inetdaemon.com/tutorials/networking/lan/define_network_segment.shtml" target="_blank">http://www.inetdaemon.com/tutorials/networking/lan/define_network_segment.shtml</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> </ol>