Ethernet segment
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A network segment is a portion of a
computer network A computer network is a set of computers sharing resources located on or provided by network nodes. The computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are ...
. The nature and extent of a segment depends on the nature of the network and the device or devices used to interconnect end stations.


Ethernet

According to the defining IEEE 802.3 standards for
Ethernet Ethernet () is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 1 ...
, a network segment is an ''electrical connection'' between networked devices using a
shared medium In telecommunication, a shared medium is a medium or channel of information transfer that serves more than one user at the same time. In order for most channels to function correctly, no more than one user can be transmitting at a time, so a ch ...
. In the original
10BASE5 10BASE5 (also known as thick Ethernet or thicknet) was the first commercially available variant of Ethernet. The technology was standardized in 1982 as IEEE 802.3. 10BASE5 uses a thick and stiff coaxial cable up to in length. Up to 100 stati ...
and 10BASE2 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
repeater In telecommunications, a repeater is an electronic device that receives a signal and retransmits it. Repeaters are used to extend transmissions so that the signal can cover longer distances or be received on the other side of an obstruction. Som ...
s (in accordance with the 5-4-3 rule for 10 Mbit Ethernet) to form a larger
collision domain In physics, a collision is any event in which two or more bodies exert forces on each other in a relatively short time. Although the most common use of the word ''collision'' refers to incidents in which two or more objects collide with great fo ...
. With
twisted-pair Ethernet Ethernet over twisted-pair technologies use twisted-pair cables for the physical layer of an Ethernet computer network. They are a subset of all Ethernet physical layers. Early Ethernet used various grades of coaxial cable, but in 1984, StarL ...
, electrical segments can be joined together using repeaters or
repeater hub In telecommunications, a repeater is an electronic device that receives a signal and retransmits it. Repeaters are used to extend transmissions so that the signal can cover longer distances or be received on the other side of an obstruction. Som ...
s as can other varieties of Ethernet. This corresponds to the extent of an OSI layer 1 network and is equivalent to the collision domain. The 5-4-3 rule applies to this collision domain. Using
switches In electrical engineering, a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another. The most common type of ...
or
bridges A bridge is a structure built to span a physical obstacle (such as a body of water, valley, road, or rail) without blocking the way underneath. It is constructed for the purpose of providing passage over the obstacle, which is usually someth ...
, multiple layer-1 segments can be combined to a common layer-2 segment, i.e. all nodes can communicate with each other through
MAC address A media access control address (MAC address) is a unique identifier assigned to a network interface controller (NIC) for use as a network address in communications within a network segment. This use is common in most IEEE 802 networking tec ...
ing or
broadcasts Broadcasting is the distribution of audio or video content to a dispersed audience via any electronic mass communications medium, but typically one using the electromagnetic spectrum (radio waves), in a one-to-many model. Broadcasting began wi ...
. A layer-2 segment is equivalent to a
broadcast domain A broadcast domain is a logical division of a computer network, in which all nodes can reach each other by broadcast at the data link layer. A broadcast domain can be within the same LAN segment or it can be bridged to other LAN segments. In ...
. Traffic within a layer-2 segment can be separated into virtually distinct partitions by using
VLAN A virtual local area network (VLAN) is any broadcast domain that is partitioned and isolated in a computer network at the data link layer ( OSI layer 2).IEEE 802.1Q-2011, ''1.4 VLAN aims and benefits'' In this context, virtual, refers to a ph ...
s. Each VLAN forms its own logical layer-2 segment.


IP

A layer-3 segment in an
IP network The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the set of communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the suit ...
is called a subnetwork, formed by all nodes sharing the same network prefix as defined by their IP addresses and the network mask. Communication between layer-3 subnets requires a router. 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.


References

{{DEFAULTSORT:Network Segment Ethernet Network architecture