Module 2:
Understanding Local
Area Networks
Agenda
1 Network Topologies
2 Ethernet Standards
Network
What is a network topology?
•
A
network topology
defines the physical connections of
hosts in a network
•
There are multiple types of topologies, including:
Bus Topology
Star Topology
•
Each host is connected to a
central connecting device
with twisted-pair cabling
• The central connecting device can be a
hub, a switch, or a SOHO router
•
This is the most commonly
used topology
•
NOTE:
two star topologies
can be connected via their
Ring Topology
Each device is connected to the
LAN using a closed loop
• NOTE: Each device is connected to two
Mesh Topology
•
Each computer connects to
every other computer in a
LAN
•
No central connecting device
•
Setup is
fault-tolerant
• allows data to be sent via multiple
What is Ethernet?
•
A standard that defines how data is sent and received between
devices
•
Most widely used standard on the Internet today
• Token Ring and FDDI are used when Ethernet is not
•
Standardized by the Institute of Electrical and Electronics
What are frames?
Devices on Ethernet networks
transmit
frames
• Sequence of bits containing a detectable
beginning and end of a packet in the stream of bits
• Include physical address information that
helps switches determine where to send data
beginning address end
info
IEEE 802.3
802.3 Version Data Transfer Rate Cable Standard Cabling Used 802.3 10 Mbps 10BASE5 Thick coaxial 802.3a 10 Mbps 10BASE2 Thin coaxial
802.3i 10 Mbps 10BASE-T Twisted pair (TP) 802.3j 10 Mbps 10BASE-F Fiber optic
802.3u 100 Mbps 10BASE-TX 100BASE-T4 100BASE-FX
TP using 2 pairs TP using 4 pairs Fiber optic
802.3ab 1000 Mbps or
1 Gbps 1000BASE-T Twisted pair 802.3z 1000 Mbps or
1 Gbps 1000BASE-X Fiber optic 802.3ae 10 Gbps 10GBASE-SR, 10GBASE-LR,
IEEE 802.3
•
Defines
carrier sense multiple access with collision
detection
(
CSMA/CD
)
• Devices share a connection
• If they send data at the same time, collisions occur • So, only one computer can transmit at a time
•
CSMA/CD allows devices to send/receive data by limiting
CSMA/CD Process
1.
Assemble a frame
2.
Check if the medium is free
a. If free, transmit a bit of the frameb. If not, don’t transmit and repeat step 2
3.
Check if a collision was detected
What is the collision detected
procedure?
If a collision is detected, then a network adapter will perform the
following steps:
1.
Send out a jam signal to stop all communication on the
medium
Peer to Peer vs.
Client/Server
The Client/Server Model
•
Servers are computers
dedicated to providing
specific types of services or
data
•
A client (a computer) uses
software to ask a server for
data or services
•
The server provides the data
or service to the client
Hey! Can you please send me an HTML
file?
Types of Servers
SERVER TYPE FUNCTION(S)
File server Store files, software, or data for access by computers on a network.
Print server Allows computers that are connected to a network to control printers on the network.
Database
server Houses a relational database made up of multiple files. Network
controller Controls accounts that are domain, as well as the devices that belong to a network. Messaging
server Provide services related to email, fax, instant messaging and collaboration. Web server Provides access to HTML documents for
computers on a network. CTI-based
Client and Server Operating Systems
To ensure functionality of both clients and servers, operating
systems are used
Client Operating Systems Server Operating Systems Windows 7 Windows Server 2008
Windows Vista
Windows XP Windows Server 2003 Windows 2000 Professional Windows 2000 Server Windows NT 4.0 Workstation
The Peer-to-Peer Model
Peers are clients that have equal
capabilities and responsibilities in
this model
• Ability to serve and request data • No server in this model
Examples of file sharing networks
• Napster • Gnutella • G2
Other technologies also take
advantage of P2P file sharing:
• Skype • VoIP
• Cloud computing
Peer Peer
Summary
1 Network Topologies
2 Ethernet Standards
