Networks: The Big Picture (an overview) ITGS 3.3 Networks Resources: Stuart Gray www.itgstextbook.com

1. Networks
The Big Picture

2. Three Great Leaps of Civilization

3. Computer Network
Single Computer Network of Computers

4. Why Network?
• Access information
• Exchange information
• Networks help people work faster and
smarter by making information available
when they need it, where they need it.
Makes distances between computers invisible.

5. Network Services and Benefits
Sharing Information
You and other network users can have
access to the same information.
Accessing remote
information
You can use your personal devices to access
information through a public information
service.
Communicating
You can exchange messages with a local
group or around the world in a quick and
paperless form of communication.
Sharing Applications
You and several other users can have
access to the same application software;
for example everyone in a work group can
upgrade simultaneously.
Sharing Network Resources
Networks allow users to share connected
devices (i.e. printers)

6. Overview of Computer Networks
• A network suggests a collection of related
things or people that are somehow
interconnected.
• In a computer network the interconnected
parts are computers, peripherals and other
devices that communicate with one another.
• A computer network may connect as few as
two computers or as many as thousands even
millions.

7. Computer Networks
This is a Network. This is not a Network.

8. Network Evolution

9. Host-Based computing

10. Decentralized computing

11. Peer-to-peer computing

12. Cloud computing

13. What is a computer network made of?
• Network Components
– Hardware: clients and servers; shared devices
(peripherals); hubs, routers and switches
– Software: applications and underlying control
software that allows the components to work
together
– Network Media: fiber optics, wireless (infrared
and radio)

14. Clients and Servers
Client computers
•Regular desktop, laptop, or mobile devices that
connect to a network to use its services.
•When connecting to a network, clients
normally have to authenticate themselves using
a username and password.

15. Clients and Servers
Servers
•Assigned responsibility for certain tasks for the
whole network, provide services for other
computers (clients)
– File servers
– Application servers
– Print servers
– Database server
– Authentication server (domain controller)
– Firewall
– Web server
– Email server

16. Shared Devices

17. Hubs, Routers and Switches
All three allow multiple computers to be
connected to them.
Difference: how each broadcasts data

18. Hubs
• Most basic and cheapest of these devices
• Broadcasts to every connected device,
including the one that sent it
• Lot of wasted bandwidth

19. Switches
• Smarter version of hubs
• Inspect received data and forward to intended
recipient
• Saves bandwidth compared to hubs

20. Routers
• Connect two or more separate networks
• Gateway through which all data entering and
leaving the network passes

21. Network Architecture
Network architecture refers to the way computers
are locally organized on a network, and the role
each takes.

22. Network Architecture
 Client/ Server Network
 Peer-to-Peer Networks (P2P)

23. Client/Server
 Centralized on one or more computers that act as
servers to the rest of the network
 Centrally manage access control and provide a
single location for file storage
Benefits
 Access from any client (not limited to one computer)
 Easier to backup files
 Better security (authenticate users and control access)

24. Client/ Server

25. P2P (Peer-to-Peer)
 No central authority or control
(all clients equal status)
 User accounts have to be made on each machine
for each use who wants access
 Less security
Benefits
 Cost efficient

26. Peer-to-Peer File Sharing
 Sharing files over the internet without a central
server
 Every user both downloads they need and uploads
the data they have.
 Quicker downloading from single server
Concern:
A means to illegally spread copyrighted material
(e.g. Napster)

27. Peer to Peer (P2P)

28. Firewalls
 Determine which data is allowed to enter and
leave a network
 Secure a computer by preventing network access
from external unauthorized access
 Control user connection to external networks

29. Proxy Servers
 Middle step between two computers
(computer on LAN and web server on Internet)
 All communication between the two passes
through proxy
 Caching, filtering, logging data

30. Types of Networks
 Local Area Networks (LAN)
 Wireless LANs (WLAN)
 Personal Area Networks (PAN)
 Metropolitan Area Networks (MANs)
 Wide Area Networks (WAN)
 Storage Area Networks (SAN)
 Virtual Private Networks (VPN)
 Virtual LAN (VLAN)

31. Protocols
• Network protocols are the rules that network
devices must follow to successfully interact
with one another.
• Protocols define the actual steps that any
device or program must take to communicate
with another device or program on the
network.

32. Protocols
TCP/ IP:
Transmission Control Protocol
Internet Protocol

33. Network Connections
 Cables and other carriers of a network’s
transmission signals are called media.
 Wired Connections
 Wireless Connections

34. Wired Connections
 Dialup
 Ethernet
 Cable Internet Access
 Fibre optic cables

35. Wireless Connections
 Wi-Fi
 WiMax
 BlueTooth
 3G and 4G

36. Network Media Characteristics
Transmission
Speed
Maximum
Length
Shielding Against
Interference
Physical properties of
different media types
make them suitable for
higher or lower rates of
data transmission.
Signals transmitted cannot
travel indefinitely.
After a given distance, the
signal begins to weaken,
lose integrity, and
experience severe
distortion.
You can partially protect
transmission by locating
network cables away from
potential sources of
interference.
Signal interference and
other factors can reduce
media reliability, requiring
transmission to be limited
to lower speeds.
Distances can be amplified
using devices such as
repeaters, bridges, or by
joining multiple networks.
Network cables are
available with varying
forms of shielding that can
lessen the signal’s
sensitivity to outside
interference.

37. Network Media Comparisons

38. Network Media Comparisons

39. Measuring Network Speed
• Bandwidth: Network’s speed; the quantity of
information that can be transmitted through a
communication medium in a given amount of
time.
• Broadband: an Internet connection (DSL or
cable modem) that offers higher bandwidth ,
and therefore faster transmission speed.
• Units of measurement: bps, Kbps, Mbps, Gbps

40. Connecting Networks Together
• Routers: Hardware device used to connect
two separate networks that decide the best
“route” for Internet transmissions.
• Gateways: Computer which acts as a bridge
between a local area network and the
Internet.

41. Preventing Unauthorized Access