packet and circuit switching

ChapterPacket 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 NetworkPacket 2 New York

Los Angeles

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

ModuleAdvantages 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

New York

Los Angeles

Las Vegas

Miami

Support for Multiple Communication SessionsSession 1 Session 2 New York

Los Angeles

Las Vegas

Miami

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 PacketsPacket 2 New York

Packet 1

Los Angeles Packet 2 may arrive earlier than Packet 1.

Miami

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

MODULEPacket 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 SwitchingInternet Server Ramp Packet M1 Miami Packet N1 New York

Los Angeles

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

Support for Multiple SessionsPacket 2 Session LA Session HU

New York

Los Angeles

Packet 1 Houston Miami

Packets are displayed on different sessions on the screen.

Applications Using MultipleSessions Sharing Collaboration Multiple access to an Internet server etc.

Packet DeliverySCREEN Packets from origin 1: N1, N2 Packets from Origin 2: M1, M2

Sharing of Word document on Internet under Microsoft NetMeeting

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 CellData Packet varies in size

Data Cell is of fixed length

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 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 NetworkSwitch Established Circuit New York

Los Angeles Circuit established and maintained for entire duration of communication.

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 SaturationEstablished Circuit New York

Los Angeles

Miami Saturation point.

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

ComparisonPacket Switching Circuit Switching _______________________________________________ Efficient use of network High overhead Computer data Audio and video transmissions are, however, possible Multiple sessions possible are easily implemented Inefficient use Low overhead Audio and video

Multiple sessions are possible, however it requires additional hardware and software

Ques