5.1 LAN Basics
• In information technology, a network is a
series of points or devices connected
together to form communication paths.
• Networks can be connected to other
networks to form internetworks.
• The Internet is a worldwide system of
• A local area network or LAN is a group of
computers and devices that share a common
communications line for the purpose of sharing
resources within in a small geographic area, such
as an office building or a school. LANs provide
full-time connectivity over high-bandwidth media,
• LANs can be small, linking only a few devices, but
often are large, linking hundreds of devices.
• A topology is the shape or map of the
network. This shape does not necessarily
correspond to the actual physical layout of
the devices on the network.
• The physical topology is the actual physical
layout of the media or cable.
• The logical topology defines how the media
is accessed by the devices or hosts.
• Ethernet is the most popular LAN technology
used today. Ethernet is popular because it has a
good balance between speed, cost, and ease of
implementation. All devices share the same
media and “listen” to make sure no other device
is sending data before they send their data. This
is called Carrier-Sense Multiple-Access
Collision Detection (CSMA-CD).
• The most commonly used Ethernet installations
use 10Base-T twisted pair copper cable.
• A protocol is a set of rules used to
communicate. You can think of it as the
language used for networks to communicate
with each other.
• Transmission Control Protocol/Internet
Protocol(TCP/IP) is a group or suite of
protocols that is widely used in networking. The
Internet uses TCP/IP.
• Many different devices are used in networking. A
few are listed here:
– A hub is a device used as a collection point for several
computers. The hub sends the data it receives back out
– A switch is a device used as a collection point for
computers that determines where to send the data by
looking at an address.
– A router is an intelligent device that connects networks
and decides the best path to send data and which port
to send it out to get it there. The Internet would not be
possible without routers.
• LAN Basics
• LAN Devices