A brief presentation about Introduction to Computer Networks.

1. Introduction to Computer Networks
INTRODUCTION TO COMPUTER NETWORKS
Muhammad Adil Raja
Roaming Researchers, Inc.
August 25, 2014

2. Introduction to Computer Networks
OUTLINE
1 USES OF COMPUTER NETWORKS
2 NETWORK HARDWARE
3 NETWORK SOFTWARE
4 REFERENCE MODELS
5 CONCLUSIONS

3. Introduction to Computer Networks
OUTLINE
1 USES OF COMPUTER NETWORKS
2 NETWORK HARDWARE
3 NETWORK SOFTWARE
4 REFERENCE MODELS
5 CONCLUSIONS

4. Introduction to Computer Networks
OUTLINE
1 USES OF COMPUTER NETWORKS
2 NETWORK HARDWARE
3 NETWORK SOFTWARE
4 REFERENCE MODELS
5 CONCLUSIONS

5. Introduction to Computer Networks
OUTLINE
1 USES OF COMPUTER NETWORKS
2 NETWORK HARDWARE
3 NETWORK SOFTWARE
4 REFERENCE MODELS
5 CONCLUSIONS

6. Introduction to Computer Networks
OUTLINE
1 USES OF COMPUTER NETWORKS
2 NETWORK HARDWARE
3 NETWORK SOFTWARE
4 REFERENCE MODELS
5 CONCLUSIONS

7. Introduction to Computer Networks
Uses of Computer Networks
USES OF COMPUTER NETWORKS I
Business Applications.
Resource Sharing.
VPNs (Virtual Private Networks).
Client-Server Model,
Web Application.
Communication Medium Between Employees.
IP Telephony.
Voice over IP (VoIP).
Desktop Sharing.
E-Commerce (Electronic Commerce).
Home Applications.
Internet access provides home users with connectivity to
remote computers.
Personalized information.
Peer-to-peer Communication.

8. Introduction to Computer Networks
Uses of Computer Networks
USES OF COMPUTER NETWORKS II
Instant Messaging.
Twitter.
Social Networks.
Facebook
Collaborative Websites – Wikis, Wikipedia.
IPTV (IP Television).
Ubiquitous Computing.
Power-line Networks.
RFID (Radio Frequency IDentification).
Mobile Users.
Connectivity.
Wireless Hotspots.
Fixed Wireless and Mobile Wireless.
Text Messaging.
Texting.
Short Message Service.

9. Introduction to Computer Networks
Uses of Computer Networks
USES OF COMPUTER NETWORKS III
Smart Phones.
GPS (Global Positioning System).
m-commerce (mobile-commerce).
NFC (Near Field Communication).
Sensor Networks.
Wearable computers.
Social Issues.
Profiling users.
Cookies.
Gmail is read by Google.
Spam.
Content intended for criminal behavior.
Phishing.
USe of CAPTCHAs.

10. Introduction to Computer Networks
Network Hardware
NETWORK HARDWARE I
PANs (Personal Area Networks).
Bluetooth.
LANs (Local Area Networks).
When LANs are used by companies, they are called
enterprise networks.
Access Point (Wireless Routers).
Base Station.
Wireless LANs – IEEE 802.11/ WiFi.
Wired LANs – IEEE 802.3/ Ethernet.
Switched Ethernet.
VLANs.
Classic Ethernet.
Power-line Networks.
Metropolitan Area Network (MAN) – covers a city.
IEEE 802.16 – WiMAX.

11. Introduction to Computer Networks
Network Hardware
NETWORK HARDWARE II
Wide Area Networks (Wide Area Networks).
A WAN covers a country or a continent.
Subnet – carries messages from host to host.
Transmission Lines – copper, optical, radio.
Switching Elements – connect two or more transmission
lines.
Routers.
Internetworks.
VPN (Virtual Private Networks.
Routing Algorithms.
Forwarding algorithms.
Internetwork.
Internetwork or internet – a collection of interconnected
networks.
Gateway – a machine that connects two or more networks.

12. Introduction to Computer Networks
Network Software
NETWORK SOFTWARE I
Protocol Hierarchies
Layered architectures.
Protocol – A set of rules for communication between
machines.
Peers in hierarchies.
Network architecture – A set of layers and protocols.
Protocl Stack – A list of protocols used by a certain system,
one protocol per layer.
Design Issues for the Layers.
Error correction.
Routing.
Protocol layering.
Internetworking.
Scalability.
Statistical multiplexing.

13. Introduction to Computer Networks
Network Software
NETWORK SOFTWARE II
Flow Control.
Congestion.
Real-time Services.
Quality of Service.
Confidentiality Authentication.
Integrity.
Connection-Oriented Versus Connectionless Service.

14. Introduction to Computer Networks
Reference Models
REFERENCE MODELS I
The OSI Reference Model.
OSI (Open Systems Interconnection).
OSI model.
The TCP/IP Reference Model.

15. Introduction to Computer Networks
Reference Models
REFERENCE MODELS II
4 REFERENCE MODELS
Layer k
Layer k + 1
Layer k - 1
Protocol
Service provided by layer k
Layer k
Layer k + 1
Layer k - 1
Figure 1-19. The relationship between a service and a protocol.
EFERENCE MODELS
FIGURE: The relationship between a service and a protocol.

16. Introduction to Computer Networks
Reference Models
THE OSI REFERENCE MODEL I
A Seven Layered Architecture.
1 Application.
2 Presentation – Concerned With the syntax and semantics
of the information transmitted.
3 Session – Dialog control, token management,
synchronization.
4 Transport.
5 Network.
6 Datalink Layer.
7 Physical Layer.
The Application Layer.
HTTP (HyperText Transfer Protocol).
FTP (File Transfer Protocol).

17. Introduction to Computer Networks
Reference Models
THE OSI REFERENCE MODEL II
Transport Layer.
Accept data from the layer above it.
Split it up into smaller units if need be.
Pass these to the network layer.
Ensure that the pieces all arrive correctly at the other end.
The Network Layer.
Controls the operation of the network.
Determine how packets are routed from the source to the
destination.
The Data Link Layer
The main task of the data lik layer is to transform a raw
transmission facility into a line that appears free of
undetected transmission errors.
It masks the real errors so that the network layer cannot
see them.

18. Introduction to Computer Networks
Reference Models
THE OSI REFERENCE MODEL III
Accomplishes this task by having the sender break the
input data into data frames.
If the service is reliable, the receiver confirms correct
receipt of each frame by sending back an
acknowledgement frame.
How to control access to the shared channel?
The medium access control sublayer.
The Physical Layer
Concerned with transmitting raw bits over a communication
channel.
The design issues: To receive a 1 as a 1 and a 0 as a 0.
Lifetime of bits (nanoseconds).
Can simultaneous transmission happen in both directions?
How to establish the initial connection.
How to tear it down when both sides are finished?
How many pins the network connector has?

19. Introduction to Computer Networks
Reference Models
THE OSI REFERENCE MODEL IV
What is each pin used for?
These design issues largely deal with mechanical, electrical
and timing interfaces.
It also deals with the physical transmission medium, which
lies below the physical layer.

20. Introduction to Computer Networks
Reference Models
THE OSI REFERENCE MODEL V42 INTRODUCTION CHAP. 1
Layer
Presentation
Application
Session
Transport
Network
Data link
Physical
7
6
5
4
3
2
1
Interface
Host A
Name of unit
exchanged
APDU
PPDU
SPDU
TPDU
Packet
Frame
Bit
Presentation
Application
Session
Transport
Network
Data link
Physical
Host B
Network Network
Data link Data link
Physical Physical
Router Router
Internal subnet protocol
Application protocol
Presentation protocol
Transport protocol
Session protocol
Communication subnet boundary
Network layer host-router protocol
Data link layer host-router protocol
Physical layer host-router protocol
Figure 1-20. The OSI reference model.
4. The layer boundaries should be chosen to minimize the information
FIGURE: The OSI reference model.

21. Introduction to Computer Networks
Reference Models
THE TCP/IP REFERENCE MODEL I
1 The Application Layer (HTTP/FTP/TELNET etc.)
2 The Transport Layer (TCP/UDP).
3 The Internet Layer (IP).
4 The Link Layer.

22. Introduction to Computer Networks
Reference Models
THE TCP/IP REFERENCE MODEL II
It is shown in Fig. 1-21 as corresponding roughly to the OSI network layer. Its
job is to permit hosts to inject packets into any network and have them travel in-
dependently to the destination (potentially on a different network). They may
even arrive in a completely different order than they were sent, in which case it is
the job of higher layers to rearrange them, if in-order delivery is desired. Note
that ‘‘internet’’ is used here in a generic sense, even though this layer is present in
the Internet.
TCP/IPOSI
Application
Presentation
Session
Transport
Network
Data link
Physical
7
6
5
4
3
2
1
Application
Transport
Internet
Link
Not present
in the model
Figure 1-21. The TCP/IP reference model.
The analogy here is with the (snail) mail system. A person can drop a se-
quence of international letters into a mailbox in one country, and with a little luck,
FIGURE: The TCP/IP reference model.

23. Introduction to Computer Networks
Reference Models
THE TCP/IP REFERENCE MODEL III
48 INTRODUCTION CHAP. 1
Link Ethernet802.11SONETDSL
IP ICMP
HTTP RTPSMTP DNS
TCP UDP
Internet
Transport
Layers Protocols
Application
Figure 1-22. The TCP/IP model with some protocols we will study.
include the Domain Name System (DNS), for mapping host names onto their net-
work addresses, HTTP, the protocol for fetching pages on the World Wide Web,
and RTP, the protocol for delivering real-time media such as voice or movies.
FIGURE: The TCP/IP model with some protocols we will study.

24. Introduction to Computer Networks
Reference Models
THE TCP/IP REFERENCE MODEL IV
ig. 1-23 as the framewo
5 Application
4 Transport
3 Network
2 Link

25. Introduction to Computer Networks
Conclusions
CONCLUSIONS
The figures have been taken from, Computer Networks,
Andrew S. Tanenbaum, 5th Edition.