Download Bright Lines

Local Area Network
Daniel Shin
CS 147, Section 3
November 18, 2008
What Is a LAN?


A LAN is a high-speed data network that
covers a small geographic area.
It typically connects workstations, personal
computers, printers, servers, and other
devices.
Characteristics

High data-transfer rates.

Small geographic range.

Lack of a need for leased telecommunication
lines.
Advantages

LANs offer computer users many advantages.

Shared access to devices and applications.

File exchange between connected users.

Communication between users via electronic
mail and other applications.
First Commercial LAN


The first commercial installation of a LAN was
in December 1977 at Chase Manhattan Bank
in New York.
It was not an Ethernet network, but a network
called ARC (Attached Resource Computer or
ARCnet).
ARCnet




It was developed by Datapoint Corporation in
1976 and announced in 1977.
ARCnet was the first widely available
networking system for microcomputers.
It became popular in the 1980s for office
automation tasks.
It is said to have since gained interest in the
embedded systems market, where certain
features of the protocol are especially useful.
Ethernet


Ethernet was
developed at Xerox
Corp.'s Palo Alto
Research Center
(PARC) in the early
1970s.
The original network
speed was just under
3Mbit/sec.
Token Ring


Token Ring uses a
special three-byte
frame called a token
that travels around
the ring.
Resides at the data
link layer (DLL) of the
OSI model.
Fiber Distributed Data Interface
(FDDI)


FDDI provides a
standard for data
transmission in a
LAN that can extend
in range up to 124
miles.
FDDI uses a dualattached, counterrotating token ring
topology.
LAN Protocols and the OSI
Reference Model
LAN Media-Access Methods



Ethernet uses carrier sense multiple access
collision detect (CSMA/CD).
Each network station listens before and after
transmitting data.
If a collision is detected, both stations wait a
random time before trying to resend.
LAN Media-Access Methods
(cont.)



Token Ring passes a special type of packet
called a token around the network.
If a network device has data to send, it must
wait until it has the token to send it.
After the data has been sent, the token is
released back on the network.
LAN Transmission Methods


LAN data transmissions fall into three
classifications: unicast, multicast, and
broadcast.
In each type of transmission, a single packet is
sent to one or more nodes.
LAN Transmission Methods
(cont.)



In a unicast transmission, a single packet is
sent from the source to a destination on a
network.
A multicast transmission consists of a single
data packet that is copied and sent to a
specific subset of nodes on the network.
A broadcast transmission consists of a single
data packet that is copied and sent to all
nodes on the network.
LAN Topologies


LAN topologies define how network devices
are organized.
Four common LAN topologies are: bus, ring,
star, and tree.
LAN Topologies (cont.)


A bus topology is a
linear LAN
architecture.
Transmissions from
network stations
create the length of
the medium and are
received by all other
stations.
LAN Topologies (cont.)

A ring topology is a
LAN architecture that
consists of a series
of devices connected
to one another by
unidirectional
transmission links to
form a single closed
loop.
LAN Topologies (cont.)


A tree topology is a
LAN architecture that
is identical to the bus
topology.
Except, branches
with multiple nodes
are possible.
LAN Devices


A repeater connects
two network
segments.
It is a physical layer
device used to
interconnect the
media segments of
an extended network.
LAN Devices (cont.)


Multiple LAN
extenders can
connect to the host
router through a
WAN.
It is a remote-access
multilayer switch that
connects to a host
router.
LAN Devices (cont.)


A hub is a physical layer device that connects
multiple user stations, each via a dedicated
cable.
Hubs are used to create a physical star
network while maintaining the logical bus or
ring configuration of the LAN.