1. Packet and Circuit Switching
Chapter
Packet and Circuit Switching

2. Chapter Objectives Explain the concept of packet switching
Give sample application areas of packet switching
Describe circuit switching
Compare and contrast packet switching with circuit switching

3. Chapter Modules Packet switching Packet switching applications
Circuit switching applications

4. Module
Packet Switching

5. Packet Switching Preview
Explain the concept of a path or a route taken by a packet
Study the difference between static and dynamic paths?
Relate appropriately the terms packet switching and circuit switching to the terms dynamic and static paths
Explore the path taken by a packets in dynamic routing when a packet travels from its origin to its destination

6. The Concept of Path in Communication
A path is a route for data to travel between two nodes in a network
Dynamic path
In this case, the path often changes from packet to packet
Example: Packet Switching
Static path
Path is initially established and it remains unchanged for the duration of the communication session
Example: Circuit Switching

7. Packet Switching Network
New
York
Los
Angeles
Packet 1
Miami

8. Salient Points of Packet Switching
Path
Each packet may take a different path to its destination
Best path is heuristically determined at each node
Packet switching
Path may be switched among packets
Hence, the term packet switching

9. Key Words
Packet and circuit switching
Dynamic and static paths

10. End of Module

11. Advantages and Disadvantages of Packet Switching
Module
Advantages and Disadvantages of Packet Switching

12. Questions
What are the major advantages and disadvantages of packet switching?
Could the Internet be called a packet switching network?
How does packet switching help in supporting multiple communication sessions?
How does a web server support multiple access to its contents? Explain in terms of packets that travel from the web server to their various destinations.

13. Questions (continued)
What are the implications of packet switching to the transmission of audio and video in real time?
How are the above problems addressed in streaming?

14. Major Advantages
Better utilization of the network segments in terms of the usage of the network paths
Ability to engage in multiple communication sessions

15. Dynamic Assignment of Paths
New
York
Los
Angeles
Las
Vegas
Miami

16. Support for Multiple Communication Sessions
New
York
Los
Angeles
Las
Vegas
Miami

17. Disadvantage or a Concern
Packets may not arrive at their destination in the order in which they were originally transmitted
The above possibility exists because of the different paths that are taken by the different packets

18. Order of Arrival of Packets
New
York
Packet 1
Los
Angeles
Miami
Packet 2 may arrive earlier than Packet 1.

19. Packet Assembly
Packets are assembled to preserve the order of transmission
Packets arriving earlier are held in a buffer
The order of arrival is critical and in certain cases the order is time sensitive as well

20. Transmission of Audio and Video in Packet Switching
Transmission of audio and video are time sensitive
Timely arrival of packet is important
The process that would ensure the orderly and timely arrival of data packets is known as streaming
Streaming also compresses the data to minimize bandwidth requirements thus ensuring that the packets have adequate bandwidth to travel to the destination in the order in which they are supposed to arrive at the destination

21. Buffering in Streaming
Streamed audio or video is often buffered to ensure that the audio or video is played continuously

22. Advantages And Disadvantages
Efficient use of the network paths
Engage in multiple sessions
Disadvantages
Additional hardware and software resources are required to assemble and route the packets
If real-time continuity is stipulated then the data must be subjected to a process known as streaming

23. Special Concerns Audio and video transmission
Streaming is used
Voice Over IP (VoIP) is designed deploy telephony over the Internet

24. Newer Advancements for Real Time Transmission of Information
Faster Internet speed
Better technology
IPv6
Better streaming technologies

25. Questions
What are the major advantages and disadvantages of packet switching?
Could the Internet be called as a packet switching network?
How does packet switching help in supporting multiple communication sessions?
How does a web server support multiple access to its contents? Explain in terms of packets that travel from the web server to their various destinations on the Internet.

26. Questions (continued)
What are the implications of packet switching to the transmission of audio and video in real time?
Relate the above to Voice over IP transmission.
How are the above problems addressed in streaming?

27. End of Module

28. Packet Switching Applications
MODULE
Packet Switching Applications

29. Questions Give a simple example of packet switching application
Relate packet switching to multiple session applications on the Internet and give examples of multiple session applications
Describe audio transmission challenges on packet-switched networks

30. Questions (Continued)
List the packet switching technologies used in WANs
Explain the emergence of the concept of fixed length packets or cells in packet switching networks
Name a cell based transmission technology and state its applications

31. Internet: An Application of Packet Switching
Packet N1
Internet
Server
New
York
Ramp
Packet M1
Los
Angeles
Miami
Server in Los Angeles supports multiple access to the web
over a packet switched connection.

32. Support for Multiple Sessions
Session LA
Session HU
Packet 2
New
York
Los
Angeles
Packet 1
Miami
Houston
Packets are displayed on different sessions on the screen.

33. Applications Using Multiple-Sessions
Sharing
Collaboration
Multiple access to an Internet server
etc.

34. Packet Delivery SCREEN Packets from Origin 2: M1, M2 Packets from
N1, N2
Sharing of Word
document on
Internet under
Microsoft
NetMeeting

35. Audio Transmission Over Packet Switching Network
Relatively high speeds are required on the network
Data compression and other techniques are used to ensure continuity know as streaming
Sample applications:
Audio streaming on the Internet
RealAudio is an example of a streaming software

36. Usage of Packet Switching
Large computer networks with multiple routers
WAN in general
Internet in particular

37. Packet Switching WAN Technologies
Past and Present
X.25 Packet Switching
Present and Near Future
Frame Relay
Present and Future
Asynchronous Transfer Mode (ATM)
ATM is also known as Cell Relay

38. ATM Asynchronous Transmission Method (ATM)
Based on fixed length packets
Switches instead of routers are used to route the information on a network
This is the emerging technology in WAN transmission
(Include more information on ATM)

39. Recollecting the Concept of Cell
Data
Packet varies in size
Data
Cell is of fixed length

40. Questions Give a simple example of packet switching application
Relate packet switching to multiple session applications on the Internet and give examples of multiple session applications
Describe audio transmission challenges on packet-switched networks

41. Questions (Continued)
List the packet switching technologies used in WANs
Explain the emergence of the concept of fixed length packets or cells in packet switching networks
Name a cell based transmission technology and state its applications

42. End of Module

43. MODULE 5
Circuit Switching

44. Questions
Explain the concepts of circuit switching. How does it function?
What are the advantages and disadvantages of circuit switching?
Name some applications of circuit switching
Compare circuit switching with packet switching

45. Circuit Switching Network
Established Circuit
Switch
New
York
Los
Angeles
Circuit established and maintained for
entire duration of communication.

46. Defining Characteristics of Circuit Switching
Establish (switch) a path (circuit) between two nodes of communication
Maintain the circuit for the full duration of communication session

47. Advantages of Circuit Switching
Continuity assured in the order of transmission
Audio can be transmitted without streaming provided adequate bandwidth is available
Otherwise streaming is necessary
The overhead is low in switching a circuit

48. Disadvantages of Circuit Switching
Inefficient use of the paths that are available within a network
This may lead to circuit saturation
Users can be locked out of the network
Multiple sessions cannot easily be implemented although it is possible to have multiple sessions

49. Circuit Saturation Established Circuit New York Los Angeles Miami
Saturation point.

50. Areas of Applications Voice/Video communications
Telephone network
Both analog and digital telecommunication lines can be circuit switched
ISDN

51. More on ISDN ISDN has two B channels and one D channel
B channel is used for data and D channel is used for monitoring and control of the data transmission
B channels are circuit switched and the D channels are packet switched

52. Comparison Packet Switching Circuit Switching
_______________________________________________
Efficient use of network Inefficient use
High overhead Low overhead
Computer data Audio and video
Audio and video
transmissions are,
however, possible
Multiple sessions possible Multiple sessions
are easily implemented are possible, however it requires additional hardware and software

53. Questions
Explain the concepts of circuit switching. How does it function?
What are the advantages and disadvantages of circuit switching?
Name some applications of circuit switching
Compare circuit switching with packet switching

54. END OF MODULE

55. END OF MODULE 5 END OF CHAPTER