1. Module 2: Understanding Local Area Networks
1.5 Understand network topologies and access methods

2. Agenda 1 Network Topologies 2 Ethernet Standards 3
Peer to Peer vs. Client/Server Models

3. Network Topologies

4. 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
Star
Ring
Mesh

5. Bus Topology
All devices are connected via copper cable in a line

6. 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 central connecting devices to form a star- bus topology

7. Ring Topology Each device is connected to the LAN using a closed loop
NOTE: Each device is connected to two other devices

8. 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 pathways if one path fails

9. Ethernet Standards

10. 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 Engineers (IEEE) as

11. 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 info
data
end

12. IEEE 802.3 802.3 Version Data Transfer Rate Cable Standard
Cabling Used
802.3
10 Mbps
10BASE5
Thick coaxial
802.3a
10BASE2
Thin coaxial
802.3i
10BASE-T
Twisted pair (TP)
802.3j
10BASE-F
Fiber optic
802.3u
100 Mbps
10BASE-TX
100BASE-T4
100BASE-FX
TP using 2 pairs
TP using 4 pairs
802.3ab
1000 Mbps or
1 Gbps
1000BASE-T
Twisted pair
802.3z
1000BASE-X
802.3ae
10 Gbps
10GBASE-SR, 10GBASE-LR, 10GBASE-ER, and so on
802.3an
10GBASE-T

13. 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 collisions

14. CSMA/CD Process Assemble a frame Check if the medium is free
If free, transmit a bit of the frame
If not, don’t transmit and repeat step 2
Check if a collision was detected
If so, implement the collision detected procedure
If not, transmit the remaining bits in the frame

15. What is the collision detected procedure?
If a collision is detected, then a network adapter will perform the following steps:
Send out a jam signal to stop all communication on the medium
Wait based on the number of collisions detected
Starts sending the remaining bits of the frame

16. Peer to Peer vs. Client/Server Models

17. 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?
Server
Client

18. 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 , fax, instant messaging and collaboration.
Web server
Provides access to HTML documents for computers on a network.
CTI-based server
Responsible for Computer Telephony Integration, which integrates a network’s telephone and computer systems.

19. 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
Windows ME/98/95
Windows NT 4.0 Server

20. 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

21. Summary 1 Network Topologies 2 Ethernet Standards 3
Peer to Peer vs. Client/Server Models