1. Living in a Network Centric World
IT305: Computer Networks – Chapter 1

2. Course Info Dr. Walid Khedr, Ph.D.
Web:
Department of Information Technology

3. Contents Living in a Network-Centric World
Communicating over the Network
Application Layer Functionality and Protocols
OSI Transport Layer
OSI Network Layer
Addressing the Network IPv4
Data Link Layer
OSI Physical Layer
Ethernet
Planning and Cabling Networks
Configuring and Testing Your Network

4. Living in a Network Centric World
This chapter provides the introduction to the course by showing how networking pervades everyday life.

5. Objectives Describe how networks impact our daily lives.
Identify the key components of any data network.
Identify converged networks.
Describe the characteristics of network architectures: fault tolerance, scalability, quality of service and security.

6. Introduction
Among all of the essentials for human existence is the need to interact with others.
Communication is almost as important to us as our reliance on air, water, food.
The creation and interconnection of robust Data Networks is having a profound effect.

7. How Networks Impact Daily Life
Early communication relies on face-to-face conversations. Nowadays, telephone, fax, interconnection of data networks etc.
Early data networks were limited to exchanging character-based information between connected computer systems.
Current networks have evolved to carry voice, video streams, text, and graphics between many different types of devices

8. Networks Supporting the Way We Learn
Courses delivered using network or Internet resources are often called online learning experiences, or e-learning.
Ex: Cisco Netacad
Online courseware and delivery offer many benefits to businesses. Among the benefits are:
Current and accurate training materials.
Availability of training to a wide audience.
Cost reduction

9. Networks Supporting the Way We Works
Business networks evolved to enable the transmission of many different types of information services, including , video, messaging, and telephony

10. Networks Supporting the Way We Play
The widespread adoption of the Internet by the entertainment and travel industries enhances the ability to enjoy and share many forms of entertainment, regardless of location.

11. Introduction
Among all of the essentials for human existence is the need to interact with others.
Communication is almost as important to us as our reliance on air, water, food.
The creation and interconnection of robust Data Networks is having a profound effect.

12. Data Networks
Current data networks have evolved to carry voice, video streams, text, and graphics between many different types of devices

13. Communication It can be in many forms and occurs in many environments
Before beginning to communicate with each other, we establish rules or agreements to govern the conversation. (Protocols)
Among the protocols that govern successful human communication are:
An identified sender and receiver
Agreed upon method of communicating (face-to-face, telephone, letter, photograph)
Common language and grammar
Speed and timing of delivery
Confirmation or acknowledgement requirements

14. The Elements of Digital Communication
Message sources devices that need to send a message to devices.
A channel, consists of the media that provides the pathway over which the message can travel from source to destination.
Messages can be sent across a network by first converting them into binary digits, or bits. These bits are then encoded into a signal that can be transmitted over the appropriate medium.

15. A Closer Look at Network Structure

16. Network Edge (End Devices)

17. The Network Core and Intermediary Devices

18. Network Core
Mesh of interconnected routers that connect the Internet’s end systems.
The fundamental question: how is data transferred through net?
Circuit Switching: dedicated circuit per call: telephone net
Packet-Switching: data sent thru net in discrete “chunks”

19. Network Core: Circuit Switching
A circuit-switched network is one that establishes a dedicated circuit (or channel) between nodes and terminals before the users may communicate.

20. Network Core: Circuit Switching
The four circuit switches are interconnected by four links.
Each of these links consists of n circuits, so that each link can support n simultaneous connections.

21. Multiplexing Circuit Switching
Frequency Spectrum: the difference between the highest and lowest frequencies available for network signals.
Frequency Division Multiplexing (FDM): The frequency spectrum of a link is shared among the connections established across the link.
The link dedicates a frequency band to each connection for the duration of the connection.
Time Division Multiplexing (TDM): Time is divided into frames of fixed duration and each frame is divided into a fixed number of time slots.
When the network establish a connection across a link, the network dedicates one time slot in every frame to the connection.

22. Multiplexing Circuit Switching
4 users
Example:
FDM
frequency
time
TDM
frequency
time

23. Network Core: Packet Switching
Packet switching splits traffic data into packets that are routed over a shared network.
Packet-switching networks do not require a circuit to be established, and they allow many pairs of nodes to communicate over the same channel.

24. Multiplexing Packet Switching
STDM method analyzes statistics related to the typical workload of each input device (printer, fax, computer) and determines on-the-fly how much time each device should be allocated for data transmission on the cable or line.

25. Four sources of packet delay
transmission A
propagation B
nodal
processing
queueing
dnodal = dproc + dqueue + dtrans + dprop
dtrans: transmission delay:
L: packet length (bits)
R: link bandwidth (bps)
dtrans = L/R
dprop: propagation delay:
d: length of physical link
s: propagation speed in medium (~2x108 m/sec)
dprop = d/s
dtrans and dprop
very different
* Check out the Java applet for an interactive animation on trans vs. prop delay 25

26. Communicating Over Networks
All networks have four basic elements in common:
Rules or agreements to govern how the messages are sent, directed, received and interpreted
The messages or units of information that travel from one device to another
A means of interconnecting these devices - a medium that can transport the messages from one device to another
Devices on the network that exchange messages with each other

27. The Elements of a Network
Devices
These are used to communicate with one another
Medium
This is how the devices are connected together
Messages
Information that travels over the medium
Rules
Governs how messages flow across network

28. The Elements of a Network

29. The Elements of a Network
Network connections can be wired or wireless
Cable: UTP, Coaxial, Optic Fibers etc
Wireless: Bluetooth, laser, microwave etc

30. The Elements of a Network
Protocols are the rules that the networked devices use to communicate with each other. The industry standard in networking today is a set of protocols called TCP/IP (Transmission Control Protocol/Internet Protocol).
On the top of TCP/IP:

31. The Elements of a Network

32. The Elements of a Network

33. The Elements of a Network

34. The Elements of a Network

35. The Elements of a Network

36. The Elements of a Network

37. The Elements of a Network

38. Converged Networks
Traditional telephone, radio, television, and computer data networks each have their own individual versions of the four basic network elements.
In the past, every one of these services required a different technology to carry its particular communication signal.

39. Converged Networks
Technology advances are enabling us to consolidate these disparate networks onto one platform - a platform defined as a converged network.

40. Network Architecture Characteristics
There are 4 basic characteristics for networks in general to meet user expectations
Fault tolerance
Scalability
Quality of service (QoS)
Security

41. A Fault Tolerant Network Architecture
Fault tolerance is the ability for a network to recover from an error, such as the failure of a device or a link (a connection between two devices).
Fault tolerance is often achieved by having redundant devices or links, so that if one fails, messages can be re-routed around the failure through other devices or links.

42. A Fault Tolerant Network Architecture
Early network type: Circuit switched connection-oriented network

43. A Fault Tolerant Network Architecture
Packet switched networks, the data are broken up into many small packets that are sent independently through the network, each finding its own best route through the network.

44. A Scalable Network Architecture
Scalability means the ability to expand to meet new demands.
Most networks are designed in a hierarchical, layered approach so new devices and links can be added without interfering with existing networks.

45. Providing Quality of Service (QoS)
Quality of Service is a control mechanism that can provide different priority to different users or data flow or guarantee a certain level of performance to a data flow in accordance with request from the application program.

46. Providing Quality of Service (QoS)

47. Providing Quality of Service (QoS)

48. Providing Network Security
Unauthorized use of communication data might have serious consequences
2 types of network security concerns that must be addressed to prevent serious consequences:
Network Infrastructure Security - physical securing of devices that provide network connectivity and preventing unauthorized access to the management software that resides on them
Content Security - protecting the information contained within the packets being transmitted over the network and the information stored on network attached devices

49. Providing Network Security
Security measures taken in a network should:
Prevent unauthorized disclosure or theft of information
Prevent unauthorized modification of information
Prevent Denial of Service
Means to achieve these goals include:
Ensuring confidentiality
Maintaining communication integrity
Ensuring availability

50. Summary

51. Reading Chapter 1 - Living in a Network-Centric World
Packet Tracer Skills Integration Activity

52. Next Lecture
Chapter 2: Communicating over the Network

53. Questions