Living in a Network Centric World

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

2. Course Info • Dr. Walid Khedr, Ph.D. • Email: khedrw@yahoo.com • Web: www.staff.zu.edu.eg/wkhedr • 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. 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.

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

6. 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

7. 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.

8. A Closer Look at Network Structure

9. Network Edge (End Devices)

10. The Network Core and Intermediary Devices

11. 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”

12. 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.

13. 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.

14. 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.

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

16. 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.

17. 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.

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

19. 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

20. 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

21. The Elements of a Network

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

23. 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:

24. The Elements of a Network

25. The Elements of a Network

26. The Elements of a Network

27. The Elements of a Network

28. The Elements of a Network

29. The Elements of a Network

30. The Elements of a Network

31. 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.

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

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

34. 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.

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

36. 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.

37. 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.

38. 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.

39. Providing Quality of Service (QoS)

40. Providing Quality of Service (QoS)

41. 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

42. 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

43. Summary

44. Reading • Chapter 1 - Living in a Network-Centric World • Packet Tracer Skills Integration Activity 1.7.1.3

45. Next Lecture • Chapter 2: Communicating over the Network

46. Questions