This document provides an overview of local area networks (LANs), including their key components, characteristics, and common physical and logical topologies. A LAN connects devices within a small physical area like a home, building, or campus. Common physical topologies include bus, star, tree and mixed configurations. Logical topologies determine how devices communicate on the network, with common examples being broadcast where all devices receive all traffic, and token passing where devices take turns sending data.

1. Fase De Planeación
Andrés Felipe Quiceno
Alejandro Álvarez
10-4
Institución Educativa Académico
SENA CTA
Cartago (valle)
Octubre 2015

3. A local area network or LAN (for the abbreviation of Local Area Network) is a
computer network covering a small area of a house, an apartment or a building.
The network topology defines the structure of a network. One part of the topology
definition is the physical topology, which is the actual layout of the wire or media.
The other part is the logical topology, which defines how the hosts access the
media to send data.
The term local network includes both hardware needed for the interconnection of
different devices and data processing software.
Characteristics:
* Technology Broadcast (diffusion) with shared transmission medium.
* Specified layout usually installed on purpose.
* Transmission capacity ranging from 1 Mbps to 1 Gbps.
* Maximum length not exceeding 3 km (One FDDI can reach 200 km)
* Use of a private media.
* The simplicity of the transmission medium used (coaxial cable, telephone cable
and optical fiber).
* The ease with which you can make changes to the hardware and software.
* Wide range and number of connected devices.
* Can be connected to other networks.
Components
Server: The server is one or those computers that will share their hardware and
software resources with other computers on the network. Its characteristics are
computing power, importance of information that stores and connection with
resources to share.
Workstation: the computers that take the role of leverage or workstations have at
their disposal the resources offered by the network and the services provided by
servers that can access.

4. Physical Topologies
Topologies most commonly used are:
 A bus topology uses only one backbone cable that is terminated at both ends . All
the hosts connect directly to this backbone. Its operation is simple and very easy to
install, but is very sensitive to traffic problems and a failure or a break in the cable
stops all transmissions.
 A star topology connects all nodes with a hub. The hub connects directly to the
nodes, sending node information source, constituting a point to point network. If a
node fails, the network continues to operate, but if the central node fails, the
transmissions are interrupted
 An extended star topology links individual stars together by connecting hubs (hubs)
or switches. This topology can extend the scope and coverage of the network.
 A hierarchical topology is similar to an extended star. But instead of linking the
hubs or switches together, the system is connected to a computer that controls the
traffic on the topology.
 The tree topology has several terminals connected in a network that branches from
a server base. A failure or breakage in the cable interrupted transmissions.
 The mixed topology is one in which a mixture of any of the other topologies
applies: bus, star or ring. Mainly we can find two mixed topologies: Star- bus and
star - ring. The most used cables are the twisted pair, coaxial cable and fiber
optics.
Logical topologies
The logical topology of a network is how the hosts communicate across the
medium. The two most common types of logical topologies are broadcast and
token passing.
Broadcast topology simply means that each host sends its data to all other hosts
on the network medium. There is no order that the stations must follow to use the
network. It is first come, Ethernet's how it works.
Topology token passing controls network access by passing an electronic token to
each host sequentially. When a host receives the token, that host can send data
over the network. If the host has no data to send, it passes the token to the next
host and the process repeats. Two examples of networks that use token passing
are Token Ring interface and Fiber Distributed Data (FDDI). Arc net is a variation
of Token Ring and FDDI. Arc net is token passing on a bus topology.