Mobility Management in Wireless CommunicationDon Norwood
The document provides an overview of mobility management in wireless networks. It discusses radio mobility and network mobility, and key aspects like location management, registration, and handoff. Mobility management functions aim to enable subscriber mobility through tracking location and delivering calls. Location is tracked through registering with location areas and updating on area crossings. Handoff allows maintaining connections as subscribers move between cells.
- GPRS is an upgrade to GSM that allows packet-based data services and efficient use of network bandwidth. It provides higher data rates than GSM and constant connectivity.
- The GPRS network architecture introduces new network elements like the SGSN and GGSN to route data packets. The SGSN manages packet data in its service area while the GGSN connects the GPRS network to external packet networks.
- Session management in GPRS includes establishing PDP contexts for data transfer sessions and location management tracks the routing area of mobile devices through routing area updates.
A wireless local area network (WLAN) uses radio frequency technology to transmit and receive data over the air, providing mobility and flexibility as an extension or alternative to wired networks. Key advantages of WLANs include productivity, convenience, lower installation costs and mobility. However, WLANs also have disadvantages such as higher costs for wireless network cards and access points, susceptibility to environmental interference, and lower bandwidth capacity compared to wired networks. Common applications of WLANs include use in corporate, education, medical and temporary settings.
Lecture 19 22. transport protocol for ad-hoc Chandra Meena
This document discusses transport layer protocols for mobile ad hoc networks (MANETs). It begins with an introduction to MANETs and the need for new network architectures and protocols to support new types of networks. It then provides an overview of TCP/IP and how TCP works, including congestion control mechanisms. The document discusses challenges for TCP over wireless networks, where packet losses are often due to errors rather than congestion. It covers different versions of TCP and their approaches to congestion control. The goal is to design transport layer protocols that can address the unreliable links and frequent topology changes in MANETs.
Transport control protocols for Wireless sensor networksRushin Shah
The document discusses traditional transport control protocols and their feasibility for use in wireless sensor networks. It describes how TCP and UDP are generally not suitable for WSNs due to their overhead and lack of features like congestion control that are needed in low power lossy networks. The document then outlines key considerations for designing new transport protocols for WSNs, including performing congestion control and reliable delivery, simplifying connection establishment, avoiding packet loss to reduce energy waste, and providing fairness across nodes. Transport protocols for WSNs need hop-by-hop approaches and mechanisms to reduce buffer usage and packet loss while conserving energy.
Datacom module 3: Data Communications Circuits, Arrangements, and NetworksJeffrey Des Binwag
Data Communication Lecture Slides covering Circuits, Arrangements, and Networks that include Network Topology, Classification of Data Communication Networks, and other related topics.
Physical channels carry information over the air interface between the mobile station and base transceiver station. Logical channels map user data and signaling information onto physical channels. There are two main types of logical channels - traffic channels which carry call data, and control channels which communicate service information. Control channels include broadcast channels which transmit cell-wide information, common channels used for paging and access procedures, and dedicated channels for signaling during calls or when not on a call. Logical channels are mapped onto physical channels to effectively transmit information wirelessly between network components in a GSM system.
Mobile technology has evolved from 1G analog networks to today's 4G/5G digital networks. Early radio technologies developed in the late 19th/early 20th centuries led to the first commercial cellular networks in the late 1970s/early 1980s (1G) providing analog voice calls. 2G digital networks in the 1990s like GSM and CDMA enabled more efficient use of spectrum and supported multiple users per channel. 3G networks beginning in the late 1990s provided improved data services and higher speeds like EDGE while laying the foundation for today's 4G/5G networks that provide robust broadband connectivity and multimedia services.
Mobility Management in Wireless CommunicationDon Norwood
The document provides an overview of mobility management in wireless networks. It discusses radio mobility and network mobility, and key aspects like location management, registration, and handoff. Mobility management functions aim to enable subscriber mobility through tracking location and delivering calls. Location is tracked through registering with location areas and updating on area crossings. Handoff allows maintaining connections as subscribers move between cells.
- GPRS is an upgrade to GSM that allows packet-based data services and efficient use of network bandwidth. It provides higher data rates than GSM and constant connectivity.
- The GPRS network architecture introduces new network elements like the SGSN and GGSN to route data packets. The SGSN manages packet data in its service area while the GGSN connects the GPRS network to external packet networks.
- Session management in GPRS includes establishing PDP contexts for data transfer sessions and location management tracks the routing area of mobile devices through routing area updates.
A wireless local area network (WLAN) uses radio frequency technology to transmit and receive data over the air, providing mobility and flexibility as an extension or alternative to wired networks. Key advantages of WLANs include productivity, convenience, lower installation costs and mobility. However, WLANs also have disadvantages such as higher costs for wireless network cards and access points, susceptibility to environmental interference, and lower bandwidth capacity compared to wired networks. Common applications of WLANs include use in corporate, education, medical and temporary settings.
Lecture 19 22. transport protocol for ad-hoc Chandra Meena
This document discusses transport layer protocols for mobile ad hoc networks (MANETs). It begins with an introduction to MANETs and the need for new network architectures and protocols to support new types of networks. It then provides an overview of TCP/IP and how TCP works, including congestion control mechanisms. The document discusses challenges for TCP over wireless networks, where packet losses are often due to errors rather than congestion. It covers different versions of TCP and their approaches to congestion control. The goal is to design transport layer protocols that can address the unreliable links and frequent topology changes in MANETs.
Transport control protocols for Wireless sensor networksRushin Shah
The document discusses traditional transport control protocols and their feasibility for use in wireless sensor networks. It describes how TCP and UDP are generally not suitable for WSNs due to their overhead and lack of features like congestion control that are needed in low power lossy networks. The document then outlines key considerations for designing new transport protocols for WSNs, including performing congestion control and reliable delivery, simplifying connection establishment, avoiding packet loss to reduce energy waste, and providing fairness across nodes. Transport protocols for WSNs need hop-by-hop approaches and mechanisms to reduce buffer usage and packet loss while conserving energy.
Datacom module 3: Data Communications Circuits, Arrangements, and NetworksJeffrey Des Binwag
Data Communication Lecture Slides covering Circuits, Arrangements, and Networks that include Network Topology, Classification of Data Communication Networks, and other related topics.
Physical channels carry information over the air interface between the mobile station and base transceiver station. Logical channels map user data and signaling information onto physical channels. There are two main types of logical channels - traffic channels which carry call data, and control channels which communicate service information. Control channels include broadcast channels which transmit cell-wide information, common channels used for paging and access procedures, and dedicated channels for signaling during calls or when not on a call. Logical channels are mapped onto physical channels to effectively transmit information wirelessly between network components in a GSM system.
Mobile technology has evolved from 1G analog networks to today's 4G/5G digital networks. Early radio technologies developed in the late 19th/early 20th centuries led to the first commercial cellular networks in the late 1970s/early 1980s (1G) providing analog voice calls. 2G digital networks in the 1990s like GSM and CDMA enabled more efficient use of spectrum and supported multiple users per channel. 3G networks beginning in the late 1990s provided improved data services and higher speeds like EDGE while laying the foundation for today's 4G/5G networks that provide robust broadband connectivity and multimedia services.
This document provides an overview of wireless sensor networks. It discusses key definitions, advantages, applications and challenges. Sensor networks can provide energy and detection advantages over traditional systems. They enable applications in various domains including military, environmental monitoring, healthcare and home automation. The document also outlines enabling technologies and discusses important considerations like network architectures, hardware components, energy consumption and optimization goals.
Topics covered in this presentation:
1. RF spectrum and GSM specifications
2. FDMA and TDMA
3. Digital Voice Transmission
4. Channel coding, Interleaving and Burst formatting
5. GMSK
6. Frame structure of GSM
7. Corrective actions against multipath fading
This document provides an overview of cellular networks. It discusses key concepts like cells, base stations, frequency reuse, and multiple access methods. It describes how location of mobile devices is managed through location updating and paging. It also covers handoff which allows active calls to continue seamlessly as users move between different cells.
This presentation describes about UMTS major components Key features, NodeB, RNC, GGSN,MSC, SGSN,VLR,HLR, Charging function, UMTS base stations and info about UMTS number allocated for MS.
This document is a project report submitted by four students for their Bachelor of Engineering degree. It examines quality of service improvement in wireless sensor networks. Specifically, it studies cluster-based routing protocols like LEACH and proposes modifications to LEACH called MODLEACH that introduces efficient cluster head replacement and dual transmitting power levels. Thresholding techniques are also incorporated into MODLEACH to further boost performance based on metrics like throughput, network lifetime and cluster head formations. The report analyzes and compares the performance of LEACH, MODLEACH, MODLEACH with hard thresholds and MODLEACH with soft thresholds through simulation and implementation in Qualnet and Matlab.
The document discusses small-scale fading and multipath propagation in wireless communications. It describes how multipath propagation leads to fading effects as multiple versions of the transmitted signal combine at the receiver. Channel sounding techniques are used to measure the power delay profile and characterize the time dispersion parameters of mobile radio channels, including mean excess delay, RMS delay spread, and maximum excess delay. Direct pulse systems, spread spectrum correlators, and frequency domain analysis are channel sounding methods discussed.
The document discusses network layer concepts including packet switching, IP addressing, and fragmentation. It provides details on:
- Packet switching breaks data into packets that are routed independently and reassembled at the destination. This allows for more efficient use of bandwidth compared to circuit switching.
- IP addresses in IPv4 are 32-bit numbers that identify devices on the network. Addresses are expressed in decimal notation like 192.168.1.1. Fragmentation breaks packets larger than the MTU into smaller fragments for transmission.
This document provides an overview of data communications and computer networks. It discusses the fundamental problem of communication and reproducing messages at different points. It also describes trends in traffic growth and new services, and reviews the components of a basic communications model. Additionally, it examines different types of networks including local area networks, wide area networks, and the Internet—covering technologies like circuit switching, packet switching, frame relay, and asynchronous transfer mode. The chapter introduces concepts like transmission media, networking, and elements that make up modern network architectures.
This document provides an overview of MIMO (Multiple Input Multiple Output) technology and its use in 802.11n wireless networks. MIMO works by using multiple antennas at both the transmitter and receiver to improve communication in three ways: by providing signal diversity to increase range and resilience, by enabling spatial multiplexing to increase data rates, and by allowing beamforming to focus signals in certain directions. The 802.11n standard will incorporate MIMO to achieve data rates up to 600Mbps using techniques like multi-path mitigation, modulation schemes, channel coding, and frame formatting adapted for MIMO transmissions. MIMO thus allows 802.11n to continue advancing wireless LAN speeds and performance.
This document provides an overview of data communication systems and computer networks. It discusses the key components of a data communication system including the message, sender, receiver, transmission medium, and protocols. It then describes different data transmission modes such as simplex, half-duplex, and full-duplex. The document also covers computer network types including LANs, MANs, and WANs, as well as network topologies like mesh, star, bus, and ring configurations. Finally, it discusses some common uses of computer networks for businesses and homes.
Cellular systems allow mobile users to communicate wirelessly using a network of base stations and switches. A mobile station communicates with the nearest base station, which connects to a mobile switching center. The switching center routes calls between mobile stations and the public switched telephone network. Coverage areas are divided into cells served by individual base stations to allow frequency reuse that improves system capacity.
ATM is a cell switching and multiplexing technology designed to unify telecommunication network infrastructures. It uses fixed length cells to transport data and signaling information. ATM networks support connections with different quality of service (QoS) levels for various media like voice, video, and data. ATM allows for predictable delivery of real-time media through constant bit rate connections while also supporting bursty data traffic.
The key characteristic of a cellular network is the ability to reuse frequencies to increase both coverage and capacity. Cellular networks divide geographic areas into smaller cells and assign different frequency groups to neighboring cells to minimize interference and allow for frequency reuse. This allows the same frequencies to be reused in different cells separated by a sufficient distance.
5G network architecture will include new functional blocks and interfaces defined by 3GPP. There are several options for deploying 5G, including standalone and non-standalone modes. When adding 5G to an existing multi-RAT site, backhaul capacity will need to be increased to at least 10Gbps to support 5G capabilities like massive MIMO and wider channel bandwidths. Migration from EPC to the new 5G core (NGCN) will require interworking between the networks during transition.
The document summarizes the evolution of mobile telephony technology from 1G to 5G. 1G introduced analog voice calls with speeds up to 2.4 kbps. 2G launched digital networks and added SMS. 2.5G combined 2G with GPRS and EDGE, enabling email and basic web browsing. 3G increased speeds to 2 Mbps, powering smartphones and multimedia. 4G provided speeds from 100 Mbps to 1 Gbps using LTE and WiMAX standards. 5G is still in development and aims to further increase speeds for applications like video calling.
GPRS is a packet-based mobile data service on GSM networks. It provides higher speed data transmission than previous GSM data services. The GPRS architecture introduces two new network nodes - SGSN and GGSN. SGSN handles mobility management and packet transmission between MS and GGSN, while GGSN connects the GPRS network to external packet networks like the Internet. GPRS enhances the GSM network by allowing dynamic allocation of bandwidth and intermittent data transmission, making it suitable for bursty, low-volume data applications.
TCP guarantees reliable delivery of data packets in the correct order, while UDP does not provide these guarantees. TCP is commonly used for applications that require reliable data transfer like HTTP and FTP. UDP is used for applications that prioritize speed over reliability, such as media streaming, VoIP, and online games. While TCP ensures error-free transmission, it introduces more overhead and latency than UDP. The choice between TCP and UDP depends on an application's requirements for reliability versus speed.
This document discusses wireless sensor network applications and energy consumption. It provides examples of WSN applications including disaster relief, environment monitoring, healthcare, and more. It then discusses various factors that influence energy consumption in sensor nodes, including operation states, microcontroller usage, radio transceivers, memory, and the relationship between computation and communication. Specific power consumption numbers are given for different components like radios, sensors, and microprocessors. The goals of optimization for WSNs are discussed as quality of service, energy efficiency, scalability, and robustness.
The IEEE 802 standards describe networking protocols for the physical and data link layers of the OSI model. The IEEE 802 committee develops these standards, with subcommittees focusing on specific technologies. The 802.5 standard defines Token Ring networks that use a logical ring topology and token passing to control access and prevent collisions. The 802.3 standard defines Ethernet networks that typically use a bus or star topology and Carrier Sense Multiple Access with Collision Detection (CSMA/CD) for network access.
In the seven-layer OSI model of computer networking, media access control (MAC) data communication protocol is a sublayer of the data link layer (layer 2). The MAC sublayer provides addressing and channel access control mechanisms that make it possible for several terminals or network nodes to communicate within a multiple access network that incorporates a shared medium, e.g. an Ethernet network. The hardware that implements the MAC is referred to as a media access controller.
The MAC sublayer acts as an interface between the logical link control (LLC) sublayer and the network's physical layer. The MAC layer emulates a full-duplex logical communication channel in a multi-point network. This channel may provide unicast, multicast or broadcast communication service.
The document discusses circuit switching and packet switching in wired area networks. It provides details on:
- Circuit switching networks require establishing dedicated circuits or paths between nodes before transmission can begin. This allows for constant transmission rates but limits flexibility.
- Packet switching breaks messages into packets that are transmitted independently through a network. Each node makes routing decisions for each packet. This allows variable transmission rates but can cause delays with high traffic.
- The two main techniques for packet switching are datagram, where each packet is routed independently, and virtual circuits, where a pre-planned route is set up before transmission.
- Other topics covered include space and time division switching used in circuit switching, characteristics of circuit switching nodes
Packet switching refers to protocols where messages are divided into packets before being transmitted. Each packet is transmitted individually and can take different routes to the destination. Once all packets arrive, they are recompiled into the original message. There are two main approaches: virtual circuits establish a pre-planned route before transmission, while datagrams treat each packet independently without connection setup. Virtual circuits provide sequencing but are less reliable if a node fails, while datagrams are more flexible but packets may arrive out of order.
This document provides an overview of wireless sensor networks. It discusses key definitions, advantages, applications and challenges. Sensor networks can provide energy and detection advantages over traditional systems. They enable applications in various domains including military, environmental monitoring, healthcare and home automation. The document also outlines enabling technologies and discusses important considerations like network architectures, hardware components, energy consumption and optimization goals.
Topics covered in this presentation:
1. RF spectrum and GSM specifications
2. FDMA and TDMA
3. Digital Voice Transmission
4. Channel coding, Interleaving and Burst formatting
5. GMSK
6. Frame structure of GSM
7. Corrective actions against multipath fading
This document provides an overview of cellular networks. It discusses key concepts like cells, base stations, frequency reuse, and multiple access methods. It describes how location of mobile devices is managed through location updating and paging. It also covers handoff which allows active calls to continue seamlessly as users move between different cells.
This presentation describes about UMTS major components Key features, NodeB, RNC, GGSN,MSC, SGSN,VLR,HLR, Charging function, UMTS base stations and info about UMTS number allocated for MS.
This document is a project report submitted by four students for their Bachelor of Engineering degree. It examines quality of service improvement in wireless sensor networks. Specifically, it studies cluster-based routing protocols like LEACH and proposes modifications to LEACH called MODLEACH that introduces efficient cluster head replacement and dual transmitting power levels. Thresholding techniques are also incorporated into MODLEACH to further boost performance based on metrics like throughput, network lifetime and cluster head formations. The report analyzes and compares the performance of LEACH, MODLEACH, MODLEACH with hard thresholds and MODLEACH with soft thresholds through simulation and implementation in Qualnet and Matlab.
The document discusses small-scale fading and multipath propagation in wireless communications. It describes how multipath propagation leads to fading effects as multiple versions of the transmitted signal combine at the receiver. Channel sounding techniques are used to measure the power delay profile and characterize the time dispersion parameters of mobile radio channels, including mean excess delay, RMS delay spread, and maximum excess delay. Direct pulse systems, spread spectrum correlators, and frequency domain analysis are channel sounding methods discussed.
The document discusses network layer concepts including packet switching, IP addressing, and fragmentation. It provides details on:
- Packet switching breaks data into packets that are routed independently and reassembled at the destination. This allows for more efficient use of bandwidth compared to circuit switching.
- IP addresses in IPv4 are 32-bit numbers that identify devices on the network. Addresses are expressed in decimal notation like 192.168.1.1. Fragmentation breaks packets larger than the MTU into smaller fragments for transmission.
This document provides an overview of data communications and computer networks. It discusses the fundamental problem of communication and reproducing messages at different points. It also describes trends in traffic growth and new services, and reviews the components of a basic communications model. Additionally, it examines different types of networks including local area networks, wide area networks, and the Internet—covering technologies like circuit switching, packet switching, frame relay, and asynchronous transfer mode. The chapter introduces concepts like transmission media, networking, and elements that make up modern network architectures.
This document provides an overview of MIMO (Multiple Input Multiple Output) technology and its use in 802.11n wireless networks. MIMO works by using multiple antennas at both the transmitter and receiver to improve communication in three ways: by providing signal diversity to increase range and resilience, by enabling spatial multiplexing to increase data rates, and by allowing beamforming to focus signals in certain directions. The 802.11n standard will incorporate MIMO to achieve data rates up to 600Mbps using techniques like multi-path mitigation, modulation schemes, channel coding, and frame formatting adapted for MIMO transmissions. MIMO thus allows 802.11n to continue advancing wireless LAN speeds and performance.
This document provides an overview of data communication systems and computer networks. It discusses the key components of a data communication system including the message, sender, receiver, transmission medium, and protocols. It then describes different data transmission modes such as simplex, half-duplex, and full-duplex. The document also covers computer network types including LANs, MANs, and WANs, as well as network topologies like mesh, star, bus, and ring configurations. Finally, it discusses some common uses of computer networks for businesses and homes.
Cellular systems allow mobile users to communicate wirelessly using a network of base stations and switches. A mobile station communicates with the nearest base station, which connects to a mobile switching center. The switching center routes calls between mobile stations and the public switched telephone network. Coverage areas are divided into cells served by individual base stations to allow frequency reuse that improves system capacity.
ATM is a cell switching and multiplexing technology designed to unify telecommunication network infrastructures. It uses fixed length cells to transport data and signaling information. ATM networks support connections with different quality of service (QoS) levels for various media like voice, video, and data. ATM allows for predictable delivery of real-time media through constant bit rate connections while also supporting bursty data traffic.
The key characteristic of a cellular network is the ability to reuse frequencies to increase both coverage and capacity. Cellular networks divide geographic areas into smaller cells and assign different frequency groups to neighboring cells to minimize interference and allow for frequency reuse. This allows the same frequencies to be reused in different cells separated by a sufficient distance.
5G network architecture will include new functional blocks and interfaces defined by 3GPP. There are several options for deploying 5G, including standalone and non-standalone modes. When adding 5G to an existing multi-RAT site, backhaul capacity will need to be increased to at least 10Gbps to support 5G capabilities like massive MIMO and wider channel bandwidths. Migration from EPC to the new 5G core (NGCN) will require interworking between the networks during transition.
The document summarizes the evolution of mobile telephony technology from 1G to 5G. 1G introduced analog voice calls with speeds up to 2.4 kbps. 2G launched digital networks and added SMS. 2.5G combined 2G with GPRS and EDGE, enabling email and basic web browsing. 3G increased speeds to 2 Mbps, powering smartphones and multimedia. 4G provided speeds from 100 Mbps to 1 Gbps using LTE and WiMAX standards. 5G is still in development and aims to further increase speeds for applications like video calling.
GPRS is a packet-based mobile data service on GSM networks. It provides higher speed data transmission than previous GSM data services. The GPRS architecture introduces two new network nodes - SGSN and GGSN. SGSN handles mobility management and packet transmission between MS and GGSN, while GGSN connects the GPRS network to external packet networks like the Internet. GPRS enhances the GSM network by allowing dynamic allocation of bandwidth and intermittent data transmission, making it suitable for bursty, low-volume data applications.
TCP guarantees reliable delivery of data packets in the correct order, while UDP does not provide these guarantees. TCP is commonly used for applications that require reliable data transfer like HTTP and FTP. UDP is used for applications that prioritize speed over reliability, such as media streaming, VoIP, and online games. While TCP ensures error-free transmission, it introduces more overhead and latency than UDP. The choice between TCP and UDP depends on an application's requirements for reliability versus speed.
This document discusses wireless sensor network applications and energy consumption. It provides examples of WSN applications including disaster relief, environment monitoring, healthcare, and more. It then discusses various factors that influence energy consumption in sensor nodes, including operation states, microcontroller usage, radio transceivers, memory, and the relationship between computation and communication. Specific power consumption numbers are given for different components like radios, sensors, and microprocessors. The goals of optimization for WSNs are discussed as quality of service, energy efficiency, scalability, and robustness.
The IEEE 802 standards describe networking protocols for the physical and data link layers of the OSI model. The IEEE 802 committee develops these standards, with subcommittees focusing on specific technologies. The 802.5 standard defines Token Ring networks that use a logical ring topology and token passing to control access and prevent collisions. The 802.3 standard defines Ethernet networks that typically use a bus or star topology and Carrier Sense Multiple Access with Collision Detection (CSMA/CD) for network access.
In the seven-layer OSI model of computer networking, media access control (MAC) data communication protocol is a sublayer of the data link layer (layer 2). The MAC sublayer provides addressing and channel access control mechanisms that make it possible for several terminals or network nodes to communicate within a multiple access network that incorporates a shared medium, e.g. an Ethernet network. The hardware that implements the MAC is referred to as a media access controller.
The MAC sublayer acts as an interface between the logical link control (LLC) sublayer and the network's physical layer. The MAC layer emulates a full-duplex logical communication channel in a multi-point network. This channel may provide unicast, multicast or broadcast communication service.
The document discusses circuit switching and packet switching in wired area networks. It provides details on:
- Circuit switching networks require establishing dedicated circuits or paths between nodes before transmission can begin. This allows for constant transmission rates but limits flexibility.
- Packet switching breaks messages into packets that are transmitted independently through a network. Each node makes routing decisions for each packet. This allows variable transmission rates but can cause delays with high traffic.
- The two main techniques for packet switching are datagram, where each packet is routed independently, and virtual circuits, where a pre-planned route is set up before transmission.
- Other topics covered include space and time division switching used in circuit switching, characteristics of circuit switching nodes
Packet switching refers to protocols where messages are divided into packets before being transmitted. Each packet is transmitted individually and can take different routes to the destination. Once all packets arrive, they are recompiled into the original message. There are two main approaches: virtual circuits establish a pre-planned route before transmission, while datagrams treat each packet independently without connection setup. Virtual circuits provide sequencing but are less reliable if a node fails, while datagrams are more flexible but packets may arrive out of order.
Circuit-switched networks establish a dedicated connection between devices before communication can occur. This involves a connection setup phase, data transfer phase, and connection teardown phase. While circuit switching guarantees bandwidth for the connection, it is inefficient because resources are allocated for the entire duration even if no data is being sent. It also has longer delays than packet-switched networks due to the setup and teardown phases. Packet-switched networks break messages into packets that are transmitted independently and may take different routes to the destination, providing more efficient use of network resources but less reliability than circuit switching.
This document discusses different types of computer network switching, including circuit switching, packet switching, and virtual circuit switching. Circuit switching establishes a dedicated connection between nodes for the duration of a call. Packet switching divides messages into packets that are routed independently through a network on a first-come, first-served basis without dedicated connections. Virtual circuit switching combines aspects of circuit switching and packet switching by establishing paths for packets through a three-phase process of setup, data transfer using local addressing, and teardown.
Packet switching breaks messages into packets that are sent over multiple routes to their destination, while circuit switching establishes a dedicated connection for the entire duration of a message transfer. Packet switching offers more efficient use of bandwidth and routes but can experience delays, while circuit switching guarantees bandwidth and quality but is less efficient. Both approaches have advantages for different types of data and network conditions.
This document provides an overview of an introduction to computer networks lecture. It outlines the topics to be covered, including an introduction to networks, layered architecture, routing, reliable transmission, flow control, and congestion control. It then discusses what a network is, how infrastructure is shared, circuit switching versus packet switching, best effort service, analogies to the mail system, and characteristics of the Internet's best effort service such as variable delay, packet loss and reordering. It compares the guarantees and efficiencies of circuit switching versus packet switching.
This document discusses different types of switched networks including circuit-switched, datagram, and virtual-circuit networks. In circuit switching, resources are reserved during setup and remain dedicated until teardown. Datagram networks allocate resources on demand without setup. Virtual circuits have aspects of both, reserving resources like circuits but packets may arrive out of order. The document also covers switch structures, comparing crossbar, multistage, and packet switches. Packet switches use buffers, queues, and scheduling at input and output ports.
This document compares circuit switching and packet switching. Circuit switching requires establishing a physical path between the source and destination, reserves the entire bandwidth in advance, and does not support store and forward transmission. In contrast, packet switching does not require a physical path, packets can travel independently, does not reserve bandwidth in advance to avoid wastage, and supports store and forward transmission. It also allows for alternate routing if the connection fails, while circuit switching does not allow for alternate routes.
El documento describe las diferencias entre conmutación de circuitos y conmutación de paquetes. La conmutación de circuitos requiere establecer una ruta dedicada entre los puntos finales, reservando los recursos de la red para una sola transmisión. La conmutación de paquetes divide los datos en paquetes que pueden tomar rutas diferentes a través de la red, sin reservar recursos, lo que permite la transmisión simultánea de múltiples usuarios.
The document discusses the key differences between packet switching and circuit switching networks. Packet switching breaks messages into packets that are sent independently over multiple routes, while circuit switching establishes a dedicated connection for the duration of a call. Some advantages of packet switching are more efficient use of bandwidth and easier scalability, while circuit switching guarantees quality of service and full bandwidth for calls.
This document defines packet switching and discusses several packet switching technologies. It begins by defining packet switching as dividing messages into packets that can follow different routes to the destination, where they are then recompiled. It then discusses three main packet switching technologies: TCP/IP, X.25, and Frame Relay. It provides details on each technology and notes that Frame Relay was implemented in Malaysia and replaced X.25 for connections within wide area networks.
There are two main switching techniques used in communications networks: circuit switching and packet switching. Circuit switching establishes a dedicated communication path between two stations for the duration of the connection. Packet switching transmits data in small packets that are routed individually through the network on a non-dedicated basis, allowing for more efficient use of bandwidth. The telephone system uses circuit switching while the internet uses packet switching, which is more suitable for data traffic since it allows for variable bandwidth and priority routing.
The document provides an introduction to 2G/3G and 4G core mobile networks. It discusses key network elements like BTS, BSC, RNC, SGSN, GGSN, eNodeB, MME, S-GW and P-GW. It provides an overview of the differences between circuit switching and packet switching. It also summarizes simplified call flows for 2G/3G packet data and 4G, highlighting the core network elements involved and interfaces between them.
The document compares the OSI model and the TCP/IP model. The OSI model consists of 7 layers and defines a standardized protocol-independent framework. The TCP/IP model has 4 layers and was developed based on the protocols used for the Internet. Key differences are that OSI has stricter layering while TCP/IP layers are more loosely defined, and TCP/IP focuses on the specific protocols used for Internetworking while OSI aims to be protocol-independent.
Circuit switching directly connects the sender and receiver through a dedicated communication path. It has high initial delay but low data delay. Message switching stores and forwards entire messages without dedicated paths, causing some delay. Packet switching breaks messages into packets that can take different routes, with virtual circuits establishing logical connections and datagrams addressing each packet individually.
Circuit switching directly connects the sender and receiver through an unbroken path. Message switching transmits entire messages from node to node without establishing a dedicated path. Packet switching breaks messages into packets that can take different routes to the destination and are reassembled upon arrival. The document discusses these three switching techniques and their advantages and disadvantages.
This document discusses different types of communication networks including traditional and high-speed LANs and WANs, as well as MANs. It describes key characteristics of these networks such as speed, distance, scope, and data rates. The document also covers switching techniques used in networks including circuit switching, packet switching, and asynchronous transfer mode (ATM). It provides examples and diagrams to illustrate how these different switching techniques work.
This document summarizes key points from Chapter 3 of the textbook "Wireless Mobile Computer Networks" by William Stallings. It discusses different types of communication networks including LANs, WANs, and MANs. It also covers circuit switching versus packet switching, components of public telecommunications networks, asynchronous transfer mode (ATM), and examples of ATM service categories.
1. The document discusses various networking devices like hubs, bridges, switches and routers. It explains their functions such as hubs being basic devices that connect computers without intelligence, bridges operating at data link layer to interconnect LANs, switches being intelligent devices that divide collision domains, and routers dividing broadcast domains and routing packets based on IP addresses.
2. It then discusses types of delays in packet switched networks including processing, queuing, transmission and propagation delays and how they accumulate. It also discusses causes of packet loss like link congestion, over-utilized devices, faulty hardware/software, and differences between wired and wireless networks.
3. Finally, it compares circuit switching which establishes dedicated connections and packet switching
In large networks, there are multiple paths between senders and receivers. Information can be switched using circuit switching, message switching, or packet switching. Circuit switching establishes a dedicated connection for the duration of a call. Message switching stores and forwards entire messages without dedicated connections. Packet switching breaks messages into packets that travel over multiple paths and are reassembled at the destination, allowing for more efficient use of bandwidth than circuit or message switching.
In large networks, there are multiple paths between senders and receivers. Information can be switched using circuit switching, message switching, or packet switching. Circuit switching establishes a dedicated connection for the duration of a call. Message switching stores and forwards entire messages without dedicated connections. Packet switching breaks messages into packets that travel over multiple paths and are reassembled at the destination, allowing for more efficient use of bandwidth than circuit or message switching.
In large networks, there are multiple paths between senders and receivers. Information can be switched using circuit switching, message switching, or packet switching. Circuit switching establishes a dedicated connection for the duration of a call. Message switching stores and forwards entire messages without dedicated connections. Packet switching breaks messages into packets that travel over multiple paths and are reassembled at the destination, allowing for more efficient use of bandwidth than circuit or message switching.
Switching Techniques - Unit 3 notes aktu.pptxxesome9832
In large networks, there are multiple paths between senders and receivers. Information can be switched using circuit switching, message switching, or packet switching. Circuit switching establishes a dedicated connection for the duration of a call. Message switching stores and forwards entire messages without dedicated connections. Packet switching breaks messages into packets that travel over multiple paths and are reassembled at the destination, allowing for more efficient use of bandwidth than circuit or message switching.
Circuit switching directly connects the sender and receiver through a dedicated physical path. Message switching transmits entire messages from node to node without a dedicated path. Packet switching breaks messages into packets that can take different routes to the destination and are reassembled, providing more efficient use of bandwidth than circuit switching.
Circuit switching directly connects the sender and receiver through a dedicated physical path. Message switching transmits entire messages from node to node without establishing a dedicated path. Packet switching breaks messages into packets that can take different routes to the destination and are reassembled, allowing for more efficient use of bandwidth but introducing complexity.
This document discusses different switching techniques used in communication networks, including circuit switching, message switching, and packet switching. It explains that packet switching overcomes the limitations of circuit and message switching by dividing messages into packets. There are two main types of packet switching: virtual-circuit switching and datagram switching. Virtual-circuit switching establishes a connection between nodes before transmitting packets, while datagram switching treats each packet independently without a pre-established connection. The optimal packet size trades off transmission time and overhead.
This document discusses different switching techniques used in digital networks, including circuit switching, message switching, and packet switching. Circuit switching establishes a dedicated connection between sender and receiver but can have long wait times and inefficient bandwidth usage. Message switching stores and forwards entire messages at each node without dedicated connections, allowing for priority and broadcasting but is incompatible with interactive applications. Packet switching breaks messages into packets that may take different paths to the destination, allowing for more efficient bandwidth sharing but requiring reassembly and possibly retransmission if packets are lost.
A network switch (sometimes known as a switching hub) is a computer networking device that is used to connect devices together on a computer network by performing a form of packet switching. A network switch is considered more advanced than a hub because a switch will only send a message to the device that needs or requests it, rather than broadcasting the same message out of each of its ports.
Switiching by Ravi Namboori Babson University USARavi Namboori
Ravi Namboori currently serves as vice president of Data Center Solutions at Unigen. Combining extensive IT experience and leadership skills, Ravi Namboori oversees the entire business unit, motivating and energizing his team to contribute to the strategic vision of the company.
Namboori brings experience from a number of Silicon Valley tech companies to Unigen. During his time as director of IT for Glu Mobile, he established the architecture and carried out the implementation of the company’s data center. Designed to be scalable and reliable, the center provided a high performance environment for Glu Mobile’s e-commerce and gaming business.
Earlier in his career, Ravi Namboori worked for Hewlett-Packard Company (HP) in the Netherlands as a network manager. In this role, he designed the LAN and call center systems for HP’s facility and carried out networking projects to client specifications.
In addition to Microsoft and Novell certifications, Namboori holds seven Cisco professional certifications including a teaching credential. He received his MBA from Babson University’s F. W. Olin Graduate School of Business and his undergraduate degree from DNR College.
Ravi Namboori, a Cisco evangelist and an IT entrepreneur, is based out of Bay Area, California. Ravi Namboori holds nine Cisco certifications, in addition to one each from Microsoft and Novell in networking. Ravi Namboori earned his MBA from The F.W. Olin Graduate School of Business at Babson College.
Refers to protocols in which messages are divided into packets before they are sent. Each packet is then transmitted individually and can even follow different routes to its destination. Once all the packets forming a message arrive at the destination, they are recompiled into the original message.
Most modern Wide Area Network (WAN) protocols, including TCP/IP, X.25, and Frame Relay, are based on packet-switching technologies. In contrast, normal telephone service is based on a circuit-switching technology, in which a dedicated line is allocated for transmission between two parties. Circuit-switching is ideal when data must be transmitted quickly and must arrive in the same order in which it's sent. This is the case with most real-time data, such as live audio and video. Packet switching is more efficient and robust for data that can withstand some delays in transmission, such as e-mail messages and Web pages.
A new technology, ATM, attempts to combine the best of both worlds -- the guaranteed delivery of circuit-switched networks and the robustness and efficiency of packet-switching networks.
This document discusses wide area network (WAN) technologies. It begins by defining WAN characteristics such as interconnecting computers over long distances using various media. It then describes different WAN technologies including circuit-switched networks, packet-switched networks, and virtual circuit networks. Specific routing protocols and concepts are explained like distance vector routing, link state routing, static versus dynamic routing. The document concludes by listing various WAN technology options for connecting sites like dial-up, leased lines, frame relay, ATM, microwave links and satellite.
Packet switching breaks messages into packets that are sent independently over multiple routes, while circuit switching establishes a dedicated channel for the duration of a call. Packet switching is more efficient for bursty traffic but can lose packets, while circuit switching guarantees delivery but wastes bandwidth for intermittent calls. Both have advantages depending on the application.
Who invented the motor car, segway, aeroplane, hang glider, and the train? This is a small presentation on the inventors who made this possible. (Their pictures, and date of invention is mentioned in the presentation.)
This document contains a series of creative writing exercises for students. It includes prompts for making up new words, recalling existing words, creating a Dadaist poem by cutting up a newspaper article, writing a fable using gloomy words, exaggerating a day using made-up words, defining literary terms, and more conceptual exercises like personifying a piece of paper or inventing new punctuation marks. The goal is to encourage imaginative thinking and experimentation with language.
This document provides an outline for writing essays, including the origin of the word "essay", the basic components and types of essays, and tips for getting started. It discusses the French and Japanese origins of the word, defines an essay as a short piece telling one's thoughts on a subject. The three basic types of essays are described as descriptive, argumentative, and narrative. Key parts of an essay include an introductory paragraph, body paragraphs with opinions and justifications, and a conclusion. Quality writing is emphasized as the most important aspect.
PhDs Produced by Punjab University from Jan to Dec 2014Water Birds (Ali)
The document lists 6 Ph.D. candidates along with their subject area, name, father's name, notification number and date, and thesis title. It includes candidates studying Zoology, Mathematics, and Chemistry with thesis topics ranging from otter distribution to cosmological issues to synthesis of heterocyclic compounds.
This document outlines syllabi and courses of reading for the M.A. Philosophy program (External Students) approved by the Board of Studies in Philosophy. It includes outlines for 5 papers in Part I and 4 papers in Part II of the M.A. examination, along with recommended books for each paper. Paper topics include history of modern Western philosophy, Muslim philosophy, moral philosophy, problems of philosophy, logic, modern philosophical movements, Muslim thought in South Asia or philosophy of religion, modern metaphysics or philosophy of mind or philosophy of education, philosophy of law or philosophy of art or Indian philosophy, and a thesis or essay.
The document outlines the syllabi and examinations for M.A. English Part I and Part II programs effective from 2002-2003. For Part I in 2003, there are 5 compulsory papers covering classical poetry, drama, novels, prose, and American literature. For Part II in 2004, the first 4 papers are compulsory covering poetry II, drama II, novel II, and literary criticism, while students must choose 1 of 4 optional papers on short stories, literature around the world, linguistics, or essay. Each paper provides reading lists and guidelines.
MPhil English Interview Schedule for 27 July 2011 (Punjab University)Water Birds (Ali)
This document provides details of an interview scheduled to take place on July 27, 2011 at 10:00 am sharp by the Department of English Language and Literature. It includes a list of 143 candidates for the interview arranged in sequential order by their roll numbers. For each candidate, it provides their serial number, roll number, full name and father's name, marks obtained, and remarks (all marked as "Pass"). The document is signed by Prof. Shaista Sonnu Sirajuddin, Chairperson.
This document summarizes the results of interviews for an M.Phil program in the Department of English Language and Literature. It lists 102 candidates who were interviewed, providing their roll number, name, father's name, interview marks out of 10, and whether they passed or failed. The majority of candidates (around 75%) received marks below the passing threshold of 5 and were noted as failing. A minority received marks above 5 and were noted as passing the interview. The document is signed by the Chairperson of the department.
This is my presentation for my MA English class. You are free to modify, share, redistribute and add to it in any way you like.
*I do not own the images used in the presentation. They are the property of their respective owners.
If your eyes are causing pain. Go through these tips. Add your tips by downloading the slide and uploading it with your name. The idea is: my eyes were hurting me and I made these slides so that anyone can follow these tips, get some sort of help and spread these slides as a gesture of thanks.
I will try to make it a longer project. But I'd be delighted if you can do that.
*The images used in the slides are the property of their respective owners. I do not own any of the pictures. This presentation is made for an educational purpose only.
This is my presentation for my MA English class. You are free to modify, share, redistribute and add to it in any way you like.
*I do not own the images used in the presentation. They are the property of their respective owners.
Things Fall Apart
WHAT DOES THE PHRASE“FALL APART” MEANS
“Collapse, break down, either physically or mentally and emotionally”
“come apart at the seams; go to pieces.”
CHINUA ACHEBE [1930 (NOW, AGE 80)]
PUBLISHER: HEINEMANN, 148 (1958 )
CHARACTERS MENTIONED IN THESE QUESTIONS
QUESTION 1
OKONKWO’S DESIRE to be strong, wealthy and respected comes from both his CULTURAL experience and his feelings about his FATHER. WHICH AFFECTS HIM MORE? (Choose, and explain why one affects more)
HE IS OKONKWO
WHAT IS DESIRE?
“Noun: A strong feeling of wanting
Verb: Strongly wish for something” Google
“he feeling that accompanies an unsatisfied state” The Free Dictionary
“Synonyms: ambition, aspiration, dream” TFD
OKONKWO’S DESIRE TO BE STRONG
Both - It comes from both feelings Cultural and feelings about father
Cultural experience
BEING STRONG
More honours for his village for bravery
TRAGIC FLAW: “My father, they have killed me!... He was afraid of being thought weak” (Achebe 43)
More valued and respected
Crowning Ceremony
OKONKWO’S DESIRE TO BE RESPECTED COMES FROM CULTURE ALSO
The desire comes from his standing among his people will positively transformed. Unlike his father with no titles.
“who had risen so suddenly from great poverty and misfortune to be one of the lords of the clan. The old man bore no ill-will towards Okonkwo. INDEED HE RESPECTED HIM FOR HIS INDUSTRY AND SUCCESS” (Achebe 19).
MORE SHEEPS
MORE TITLES
MORE SHEEP/ANIMALS + MORE TITLES + MORE MONEY = MORE RESPECT, MORE WIVES
Being strong meant being a warrior, a defender, a protector and a leader – Ibo people respected warriors.
He desires to be somebody instead of being nobody like this father.
OKONKWO AND UNOKA (HIS FATHER ARGUING)
Being Wealthy
Warrior awards
The more the animals the more the respect
The important question of what affects him more?
His feelings about his father affects him more
Feelings about his father changed his life
Father’s GUILT ‘of being nobody’ made him struggle
The guilt of suicide committed by his father
WHAT AFFECTS HIM MORE?
“whenever he was angry and could not get his words out quickly enough, he would use his fists. He had NO PATIENCE WITH UNSUCCESSFUL MEN. He had had no patience with his father” (Achebe 3).
At least at the end (BEING A WARRIOR) he realizes its TIME TO SACRIFICE his own self. Even though, he knew it is the most difficult part in his life. Okonkwo was all the time running away from this embarrassment of dying like this father. And now being like his father meant his salvation for himself and his people.
... (text displayed as much as the system allows)
This is my presentation for my MA English class. You are free to modify, share, redistribute and add to it in any way you like.
*I do not own the images used in the presentation. They are the property of their respective owners.
ALTITUDE. Vertical distance of an aircraft or object above a given reference, such as ground or sea level.
AMPLIFIER. An electronic device used to increase signal magnitude or power.
AMPLITUDE MODULATION (AM). A method of impressing a message upon a carrier signal by causing the carrier amplitude to vary proportionally to the message waveform.
ANTENNA SYSTEM. Routes RF energy from the transmitter, radiates the energy into space, receives echoes, and routes the echoes to the receiver.
A presentation prepared by my friend's friend. I have done no editing at all, I'm just uploading the presentation as it is.
This is a very basic traffic light circuit that is built around the TTL family 74145.
The circuit is stepped by a 555 astable oscillator. The rate at which the timer IC changes is determined by the value of resistance.
The Oscillators output is divided by a 74LS90 divider that produces a (BCD) output.
There are four counts for RED, two counts for ORANGE and four counts for GREEN.
A presentation prepared by my friend's friend. I have done no editing at all, I'm just uploading the presentation as it is.
This presentation will cover:
Report purpose and planning
Report format and organization
Headings and language
Visual design
Source documentation
Finishing touches
A presentation prepared by my friend's friend. I have done no editing at all, I'm just uploading the presentation as it is.
Chapter 3 History and Geography The Foundations of Culture Water Birds (Ali)
The importance of history and geography in the understanding of international markets
The effects of history on a country’s culture
How culture interprets events through its own eyes
How the United States moved west and how this more affected attitudes
The effect of geographic diversity on economic profiles of a country
Why markets need to be responsive to geography of a country
Economic effects of controlling population growth versus aging population
Communications are an integral part of international commerce
How to Build a Module in Odoo 17 Using the Scaffold MethodCeline George
Odoo provides an option for creating a module by using a single line command. By using this command the user can make a whole structure of a module. It is very easy for a beginner to make a module. There is no need to make each file manually. This slide will show how to create a module using the scaffold method.
This slide is special for master students (MIBS & MIFB) in UUM. Also useful for readers who are interested in the topic of contemporary Islamic banking.
বাংলাদেশের অর্থনৈতিক সমীক্ষা ২০২৪ [Bangladesh Economic Review 2024 Bangla.pdf] কম্পিউটার , ট্যাব ও স্মার্ট ফোন ভার্সন সহ সম্পূর্ণ বাংলা ই-বুক বা pdf বই " সুচিপত্র ...বুকমার্ক মেনু 🔖 ও হাইপার লিংক মেনু 📝👆 যুক্ত ..
আমাদের সবার জন্য খুব খুব গুরুত্বপূর্ণ একটি বই ..বিসিএস, ব্যাংক, ইউনিভার্সিটি ভর্তি ও যে কোন প্রতিযোগিতা মূলক পরীক্ষার জন্য এর খুব ইম্পরট্যান্ট একটি বিষয় ...তাছাড়া বাংলাদেশের সাম্প্রতিক যে কোন ডাটা বা তথ্য এই বইতে পাবেন ...
তাই একজন নাগরিক হিসাবে এই তথ্য গুলো আপনার জানা প্রয়োজন ...।
বিসিএস ও ব্যাংক এর লিখিত পরীক্ষা ...+এছাড়া মাধ্যমিক ও উচ্চমাধ্যমিকের স্টুডেন্টদের জন্য অনেক কাজে আসবে ...
Macroeconomics- Movie Location
This will be used as part of your Personal Professional Portfolio once graded.
Objective:
Prepare a presentation or a paper using research, basic comparative analysis, data organization and application of economic information. You will make an informed assessment of an economic climate outside of the United States to accomplish an entertainment industry objective.
The simplified electron and muon model, Oscillating Spacetime: The Foundation...RitikBhardwaj56
Discover the Simplified Electron and Muon Model: A New Wave-Based Approach to Understanding Particles delves into a groundbreaking theory that presents electrons and muons as rotating soliton waves within oscillating spacetime. Geared towards students, researchers, and science buffs, this book breaks down complex ideas into simple explanations. It covers topics such as electron waves, temporal dynamics, and the implications of this model on particle physics. With clear illustrations and easy-to-follow explanations, readers will gain a new outlook on the universe's fundamental nature.
Main Java[All of the Base Concepts}.docxadhitya5119
This is part 1 of my Java Learning Journey. This Contains Custom methods, classes, constructors, packages, multithreading , try- catch block, finally block and more.
हिंदी वर्णमाला पीपीटी, hindi alphabet PPT presentation, hindi varnamala PPT, Hindi Varnamala pdf, हिंदी स्वर, हिंदी व्यंजन, sikhiye hindi varnmala, dr. mulla adam ali, hindi language and literature, hindi alphabet with drawing, hindi alphabet pdf, hindi varnamala for childrens, hindi language, hindi varnamala practice for kids, https://www.drmullaadamali.com
A Strategic Approach: GenAI in EducationPeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
2. Introduction
The long-haul circuit-switching telecommunications network was
originally designed to handle voice traffic
A key characteristic of circuit-switching networks is that resources
within the network are dedicated to a particular call. For voice
connections, resulting circuit will enjoy a high percentage of
utilization.
However, as the circuit-switching network began to be used
increasingly for data connections, two shortcomings became
apparent:
In a typical user host data connection (e.g., personal computer user
logged on to a database server), much of the time the line is idle. Thus,
with data connections, a circuit-switching approach is inefficient.
In a circuit-switching network, the connection provides for transmission
at constant data rate. Thus, each of the two devices that are connected
must transmit and receive at the same data rate as the other; this limits
the utility of the network in interconnecting a variety of host computers
and terminals.
3. Solving the problem
To understand how packet switching addresses these
problems, let us briefly summarize packet-switching
operation.
Data are transmitted in short packets. A typical upper
bound on packet length is 1000 octets (bytes).
If a source has a longer message to send, the message
is broken up into a series of packets
Each packet contains a portion of the user's data plus
some control information.
The control information, at a minimum, includes the
information that the network requires in order to be able
to route the packet through the network
At each node en route, the packet is received, stored
briefly, and passed on to the next node.
4. The Approach
This approach has a number of advantages over circuit
switching:
Line efficiency is greater, as a single node-to-node link
can be dynamically shared by many packets over time.
The packets are queued up and transmitted as rapidly as
possible over the link.
By contrast, with circuit switching, time on a node-to-
node link is pre-allocated using synchronous TDM.
Much of the time, link may be idle because a portion of
its time is dedicated to a connection which is idle.
Packet-switch network can perform data-rate conversion.
Two stations of different data rates can exchange
packets because each connects to its node at its proper
data rate.
5. The Approach II
When traffic becomes heavy on a circuit-switching
network, the network refuses to accept additional
connection requests (Blocked) Until load decreases.
On a packet-switching network, packets are still
accepted, but delivery delay increases.
Priorities can be used.
It can transmit the higher-priority packets first. These
packets will therefore experience less delay than
lower-priority packets.
6. Switching Technique
A station has a message to send through a packet-switching
network that is of length greater than the maximum packet
size.
It therefore breaks the message up into packets and sends
these packets, one at a time, to the network.
A question arises as to how the network will handle this stream
of packets as it attempts to route them through the network
and deliver them to the intended destination
There are two approaches that are used in contemporary
networks:
datagram &
Virtual circuit
7. Datagram approach
Each packet is treated independently, with no reference to packets
that have gone before.
Some implication of this approach.
When the data is sent over the network it might be possible that the
data packets if broken take different route to its destination
They totally dependent upon the forwarding node for routing the
packets
Possibly the data packet which was last may reach the destination
first.
It is possible for a packet to be destroyed in the network (if a packet
switching node crashes momentarily)
if packets get lost, the destination node has no way to know that one
of the packets in the sequence has been lost.
it is up to receiver to detect loss of a packet and recovers it.
8. Virtual circuitsIn the virtual-circuit approach, a preplanned route is established
before any packets are sent
It first sends a special control packet, referred to as a Call-Request
packet
Nodes decides to route the request and all subsequent packets to other
nodes
If Station is prepared to accept the connection, it sends Call-Accept
packet back to station via nodes
Stations can then exchange data over the route that has been
established.
As route is fixed for the duration of the logical connection, it is
somewhat similar to a circuit-switching network, and is referred to as
a virtual circuit
Each packet also contains a virtual-circuit identifier and data
Eventually, one of the stations terminates the connection
with a Clear-Request packet
At any time, each station can have more than one virtual circuit to any
other station and can have virtual circuits to more than one station.
9. Advantages of datagram
In datagram approach the call setup phase is avoided
Datagram delivery will be quicker.
It is more primitive and more flexible
Good with Congestion control-
Unlike virtual circuits, packets follow a predefined route, it is
difficult to adapt to congestion
Datagram delivery is inherently more reliable
Alternate route that bypasses congestion and failure
A datagram-style of operation is common in inter-
networks
10. Characteristic of the virtual-circuit
In virtual-circuit (VC) a route between stations is set
up prior to data transfer
That does not mean its a dedicated path
packet is still buffered at each node, and queued for
output over a line
With virtual circuits, the node does not make a
routing decision for transferring each packet
11. Advantages of VC
If two stations wish to exchange data over an
extended period of time
network may provide services related to the virtual
circuit, including sequencing and error control
because all packets follow the same route, they arrive
in the original order
If dara arrives with an error, node can request a
retransmission of that packet from previous node
12. Packet size
One important issue is the packet size to be sent on
network
There is a significant relationship between packet size
and transmission time
13. Packet size
•In this Fig, it is assumed
that there is a virtual
circuit from station
X through nodes a and b
to station Y.
•The message comprises
30 octets, of and each
packet contains 3 octets
of control information
•Placed at beginning of
each packet and is
referred to as a header.
14. Packet sizeIf the sent packet consists of 33 octets (3 of header plus 30 of data), then
Packet is first transmitted from station X to node a (Figure a).
When the entire packet is received, it can then be transmitted from a to b.
When the entire packet is received at node b, it is transferred to station Y.
The total transmission time at the nodes is 99 octet-times
(33 octets X 3 packet transmissions = 99 Octet-times).
So if we break up the message into more packets (Packet + Control info)
So because of overlapping in transmission, the total transmission time of 2
packets drops to 72 octet-times, for 5 packets it drop to total of 63
However, this process of using more and smaller packets eventually results
in increased, rather than reduced, delay as in Fig d;
This is because each packet contains a fixed amount of header, and more
packets means more of these headers.
We did not consider processing and queuing delays at each node.
Extremely small packet size (53 octets) can result in an efficient network
design.
15. Comparison of Circuit Switching
& Packet Switching
Performance
A simple comparison of circuit switching and the two forms of packet
switching are provided in next slides.
The figure shows transmission of a message across four nodes. from a
source attached to node 1 to a destination attached to node 4.
In that figure, we are concerned with three types of delay:
Propagation delay. The time it takes a signal to propagate from one node
to the next. This time is generally negligible in ms
Transmission time. The time it takes for a transmitter to send out a block
of data. For example, it takes 1 s to transmit a 10,000-bit block of data on a
10-kbps line.
Node delay. The time it takes for a node to perform the necessary
processing as it switches data.
However, actual performance depends on a host of factors, including
the size of the network, its topology, the pattern of load, and the
characteristics of typical exchanges.
16. Circuit switch
In circuit switching, there is a of delay in
message before it is sent.
First, a call request signal is sent through the
network in order to set up a connection to
the destination.
A processing delay is faced at each node
during the call request
This time is spent at each node setting up the
route of the connection.
On the return, this processing is not needed
because the connection is already set up
Once set up, the message is sent as a single
block, with no noticeable delay at the
switching nodes.
17. Virtual Circuit
Virtual-circuit packet similar to circuit switching.
A virtual circuit is requested using a call-request
packet, which incurs a delay at each node.
The virtual circuit is accepted with a call-accept
packet.
In contrast to the circuit-switching case, the call
acceptance also experiences node delays, even
though the virtual circuit route is now established
the reason is that this packet is queued at each
node and must wait its turn for retransmission.
On establishment of virtual circuit message is
transmitted in packets.
This phase can be no faster than circuit switching,
Some delay are present at each node in the path;
worse, this delay is variable and will increase with
increased load.
18. Datagram packet switching
Datagram packet switching does not require a
call setup.
Thus for short messages it is faster than virtual-
circuit packet switching and perhaps circuit
switching.
However, because each individual datagram is
routed independently, the
processing for each datagram at each node may
be longer than for virtual-circuit packets.
Thus, for long messages, the virtual-circuit
technique may be superior.
19. Transparency of circuit switching
Circuit switching is essentially a transparent service.
Once a connection is established, a constant data rate is provided to
the connected stations
But not the case with packet switching, which typically introduces
variable
delay, so that data arrive in a choppy manner.
With datagram packet switching, data may arrive in a different order
than they were transmitted.
An additional consequence of transparency is that there is no
overhead required to accommodate circuit switching.
Once a connection is established, the analog or digital data are passed
through, as is, from source to destination.
For packet switching, analog data must be converted to digital before
transmission and each packet includes overhead bits, such as the
destination address.
20. External and internal operation
Depends upon the characteristics of packet switching
weather it is using data-grams or virtual circuits.
There are two dimensions of these characteristics.
At the interface between a station and network node
Network may provide
Connection-oriented
Connectionless service
21. Connection-oriented service
A station performs a call request to set up a logical connection to
another station
All packets presented to the network are identified as belonging to
a particular logical connection and are numbered sequentially
The logical connection is usually referred to as a virtual circuit and
the connection-oriented service is referred to as an external virtual
circuit service
Where as the external service is distinct from the concept of
internal virtual circuit operation a good example is X.25
X.25 - This standard is almost universally used for interfacing to
packet-switching networks and is employed for packet switching in
ISDN.
22. Connectionless
With connectionless service, the network only agrees
to handle packets independently, and may not deliver
them in order or reliably, known as an external
datagram service
This concept is distinct from that of internal
datagram operation.
Internally the network may actually construct a fixed
route between endpoints (virtual circuit), or it may
not (datagram).
23.
24. Design decisions
These internal and external design decisions need not match
External virtual circuit, internal virtual circuit.
The user requested virtual circuit, a dedicated route through the network.
All packets follow that same route.
External virtual circuit, internal datagram.
Packets are handled separately. Thus, different packets for the same
external virtual circuit may take different routes. Which are buffered at the
destination node, in proper order.
External datagram, internal datagram.
Each packet is treated independently from both the user's and the
network's point of view.
External datagram, internal virtual circuit.
The external user does not see any connections, as it simply sends packets
one at a time. The network, however, sets up a logical connection between
stations for packet delivery and may leave such connections in place for an
extended period, so as to satisfy estimated future needs
25.
26. Choice
Which one to choose in virtual circuits and data-grams out of both
internal and external.
This will depend on the specific design objectives for the
communication network and the cost factors that prevail.
The datagram service, allows efficient use of the network as no call setup
and no need to hold up packets while a packet in error is retransmitted.
This latter feature is desirable in some real-time applications.
The virtual-circuit service can provide end-to-end sequencing and error
control; this service is attractive for supporting connection-oriented
applications such as file transfer and remote-terminal access.
Virtual-circuit service is much more common than the datagram
service.
The reliability and convenience of a connection-oriented service is
seen as more attractive than the benefits of the datagram service.