Chapter Packet and Circuit Switching. Chapter Objectives Explain the concept of packet switching Give sample application areas of packet switching Describe.

Chapter

Packet and Circuit Switching

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

Chapter Modules

• Packet switching• Packet switching applications• Circuit switching applications

Module

Packet Switching

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

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

Packet Switching Network

Los Angeles

NewYork

Packet 2

Packet 1 Miami

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

Key Words

• Packet and circuit switching• Dynamic and static paths

End of Module

Module

Advantages and Disadvantages of Packet

Switching

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.

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?

Major Advantages

• Better utilization of the network segments in terms of the usage of the network paths

• Ability to engage in multiple communication sessions

Dynamic Assignment of Paths

Los Angeles

NewYork

Miami

LasVegas

Support for Multiple Communication Sessions

Los Angeles

NewYork

Miami

LasVegas

Session 1

Session 2

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

Order of Arrival of Packets

Los Angeles

NewYork

Packet 2

Packet 1

Miami

Packet 2 may arrive earlier than Packet 1.

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

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

Buffering in Streaming

• Streamed audio or video is often buffered to ensure that the audio or video is played continuously

Advantages And Disadvantages

• Advantages– 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

Special Concerns

• Audio and video transmission– Streaming is used

• Voice Over IP (VoIP) is designed deploy telephony over the Internet

Newer Advancements for Real Time Transmission of

Information

• Faster Internet speed• Better technology

– IPv6– Better streaming technologies

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.

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?

End of Module End of Module

MODULE

Packet Switching Applications

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

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

Internet: An Application of Packet

Switching

Los Angeles

NewYork

Packet N1

Packet M1

Miami

Server in Los Angeles supports multiple access to the webover a packet switched connection.

InternetServer

Ramp

Support for Multiple Sessions

Los Angeles

NewYork

Packet 2

Packet 1Miami

Packets are displayed on different sessions on the screen.

Houston

Session LASession HU

Applications Using Multiple-Sessions

• Sharing• Collaboration• Multiple access to an Internet

server• etc.

Packet Delivery

Sharing of Worddocument onInternet underMicrosoft NetMeeting

Packets fromorigin 1:N1, N2

Packetsfrom Origin 2:M1, M2

SCREEN

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

Usage of Packet Switching

• Large computer networks with multiple routers

• WAN in general• Internet in particular

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

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)

Recollecting the Concept of Cell

Packet varies in size

Cell is of fixed length

Data

Data

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

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

End of ModuleEnd of Module

MODULE 5

Circuit Switching

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

Circuit Switching Network

Los Angeles

NewYork

Circuit established and maintained for entire duration of communication.

Established CircuitSwitch

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

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

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

Circuit Saturation

Los Angeles

NewYork

Established Circuit

Saturation point.

Miami

Areas of Applications

• Voice/Video communications– Telephone network

• Both analog and digital telecommunication lines can be circuit switched

• ISDN

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

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

Comparison

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

END OF MODULE END OF MODULE

END OF MODULE 5 END OF MODULE 5

END OF CHAPTER END OF CHAPTER