...__________________________ «_____»_________________________2012 год Алматы 2012 СОДЕРЖАНИЕ 1 Annotation 3 2 PACKET SWITCHING 3 3 КОММУТАЦИЯ ПАКЕТОВ 6 ТЕРМИНОЛОГИЧЕСКИЙ СЛОВАРЬ 10 СПИСОК ЛИТЕРАТУРЫ 11 Annotation This text describes packet switching, its modes and history. The main topic of this text is how packet switching works. Packet switching is a digital networking communications method that groups all transmitted data – regardless of content, type, or structure – into suitably sized blocks, called packets. The concept of switching small blocks of data was first explored by Paul Baran in the early 1960s. Independently, Donald Davies at the National Physical Laboratory (NPL) in the UK had developed the same ideas a few years. Two major packet switching modes exist; (1) connectionless packet switching, also known as datagram switching, and (2) connection-oriented packet switching, also known as virtual circuit switching. In the first case each packet includes complete addressing or routing information. 1 PACKET SWITCHING Packet switching is a digital networking communications method that groups all transmitted data – regardless of content, type, or structure – into suitably sized...
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...TMC1254 Communication and Computer Network Semester 2 2013/2014 Switching 1 Learning Unit Objectives • Understand the concept of switching. • Understand and able to differentiate between different types of switching. 2 • How many connection per device? 3 Introduction • A network is a set of connected devices • How to connect them for communication? – Using mesh topology but wasteful – Used switching • Switched network consists of a series of interlinked nodes, called switches (temporary connection btw 2 or > devices) 4 Switched network 3 Simple Switching Network 6 Taxonomy of switched networks 7 Circuit Switched Networks Three Phases Efficiency Delay 8 9 CIRCUIT-SWITCHED NETWORKS • consists of a set of switches connected by physical links. • Connection between two stations is a dedicated path made of one or more links. – However, each connection uses only one dedicated channel on each link. – Each link is normally divided into n channels by using FDM or TDM. 10 How circuit-switched network works? • Consist of three phases: 1. Setup phase: – When end system A needs to communicate with end system M, system A need to request a connection to M that must accepted by all switches as well as by M – Allocation of resources as needed 2. Data transfer: data is transferred from node to node. 3. Teardown: After all data have been transferred, the circuits are torn down. – Circuit is terminated, de-allocation...
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...ABSTRACT In the context of the rapid growth of mobile computing penetration in developing countries, mobile telephony is currently considered to be particularly important for such development. Yet, until recently, very little systematic evidence was available that shed light on the developmental impacts of mobile computing. The objective of this paper is to evaluate the problems and prospects of mobile computing in Nigeria. The paper will be analyzed by theme in order to provide a thematic overview as well as a comparative analysis of the development role of mobile computing. In exploring the evidence from completed projects as well as the foci of new projects, the paper summarizes and critically assesses the key findings and suggests possible avenues for future research. CHAPTER ONE INTRODUCTION The fusion of computer and telecommunication technologies has heralded the age of information superhighway over wire-line and wireless networks. Mobile cellular communication systems and wireless networking technologies are growing at an ever-faster rate, and this is likely to continue in the foreseeable future. Wireless technology is presently being used to link portable computer equipment to corporate distributed computing and other sources of necessary information. Wide-area cellular systems and wireless LANs promise to make integrated networks a reality and provide fully distributed and ubiquitous mobile communications, thus bringing an end to the tyranny of geography. Higher...
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...a single twisted pair of wires, an analog circuit, with the Telco performing circuit switching to switch the analog circuit through the Telco. 2. Which of the following are services that Telco’s have offered as WAN services over the years? (Choose two answers.) Answer: A, Switched analog circuits. B, Dedicated Digital circuits 3. This chapter claims that IP routers work well as devices that connect to many different types of interfaces, including LANs and WANs. Which of the following answers list the reasons why routers do well in this role? (Choose two answers.) Answer B. Router vendors sell many different types of physical interface cards, so the routers have the right physical connectors to connect to different types of networks. D. Routers discard old data-link headers and insert new data-link headers as part of their logic, which treats each interface’s lower-layer details as independent from each other. 4. An enterprise network has many routers that connect to both a LAN as well as the WAN. Which one of the following statements best describes how routers typically use and think about their WAN connections? Answer: B. The question specifically asks for the one best answer and for the routers’ perspective. In this case, the answer about routers ignoring Layers 1 and 2 is simply incorrect; routers must know about these layers to receive and send data. Routers can send IP packets to user host destinations on the WAN itself, but because most user devices sit on a LAN...
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...You need to consider several factors before implementation can begin—and a solid understanding of all the connection types is critical to making the right choice. Most carriers offer three connection types: 1. Circuit-switched connections 2. Packet-switched or cell-switched connections 3. Dedicated connections Each type of connection has its advantages and disadvantages. This article will summarize what each connection type has to offer, with consideration given to bandwidth, availability, cost, and ease of management. Circuit-switched connections Circuit-switched connections are currently the most popular type of WAN connection. Circuit switching transmits data streams and datagrams across dedicated physical circuits. To provide asynchronous dial-in and ISDN services, the telephone companies use circuit switching. Asynchronous dial-in The public switched telephone network (PSTN) uses circuit-switched technology to provide asynchronous services (otherwise known as normal telephone service). Asynchronous dial-in connections offer a low-bandwidth, easily managed, cost-effective solution that is available almost anywhere in the world. ISDN Integrated Services Digital Network (ISDN) is a digital circuit switching technology used to transport voice, data, and video. With speeds up to 1.54 Mbps (T1) in North America and 2.048 Mbps (E1) in Europe, ISDN is a low- to medium-bandwidth solution with relatively low cost. However, availability is somewhat limited and...
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...The biggest difference between Frame Relay and X.25 is that X.25 guarantees data integrity and network managed flow control at the cost of some network delays. Frame Relay switches packets end to end much faster, but there is no guarantee of data integrity at all. Frame Relay is cost effective, partly due to the fact that the network buffering requirements are carefully optimized. Compared to X.25, with its store and forward mechanism and full error correction, network buffering is minimal. Frame Relay is also much faster than X.25: the frames are switched to their destination with only a few byte time delay, as opposed to several hundred milliseconds delay on X.25. An evolution beyond the X.25 protocol, Frame Relay is a network interface standard based on statistical multiplexing. By combining the flexibility of X.25 packet protocol with the performance of private lines, Frame Relay Service can move data much more efficiently than the packet protocol. In fact, Frame Relay Service streamlines the processing steps associated with X.25 error detection/correction and routing procedures. Frame Relay technology takes advantage of highly accurate digital networks with their reduced line errors and intelligent network end point devices with their end-to-end error checking protocols. The reduced per packet processing time allows you to process more user data. Also, the upgrade to Frame Relay Service is simple and cost effective because Frame Relay Service is based on the HDLC protocol...
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...13. B,C 14. C 15. B,C 16. B,D 17. C 18. D 19. C,D 20. B,C Key Terms: Switched circuit- A circuit created by the phone company in reaction to signaling (the user tapping telephone keys or a modem sending in the same digits), with the telco tearing down the circuit when the user is finished. Dedicated circuit- An electrical circuit created by a telco on behalf of a customer, with the circuit staying up all the time, dedicated for use by the one customer that ordered the circuit. Also known as a leased line, leased circuit, and point-to-point line Circuit switching- The overall process by which a series of telco devices called circuit switches connect a circuit from one customer device to the other, with the device’s logic taking incoming bits on one segment in the link and forwarding those bits out the matching outgoing segment, without storing the bits Packet switching- the process of forwarding customer data in a WAN by looking at the header of the messages sent into the WAN by the customer and making a per-message decision as to where to forward each message. Leased line- A physical link between two locations, provided by a telco, that allows two-way communication between sites. Because the customer does not own the physical line between sites, but rather pays a monthly fee for the service, it is called a leased service or leased line. Also known as a dedicated circuit, leased circuit, and point-to-point line Time-division Multiplexing- A type...
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...physical, data link, network, and transport layers. The physical layer is layer 1, which is the bottom layer of the OSI model. It transmits and receives signals, as well as specifying the physical details of Ethernet cables and other hardware behavior. The functions of the physical layer include managing hardware connections, handle sending and receiving of binary signals and encoding of bits. (Cengage Learning, 2011) The data link layer, layer 2, is responsible for managing access to the network and provides physical addressing, device-to-device delivery of frames, media access control, and MAC addresses. Layer 3 is the network layer, which handles the logical addressing and routing of PDUs across internetwork. It handles packet routing and access control through packet inspection. Transport layer is the 4th layer of the OSI model and it is responsible for delivery of data streams across the network. The transport layer not only ensures reliable delivery of data but it also breaks data into segments, handles sequencing and provides flow control. The upper layers of the OSI model consist of three layers which include the session layer, presentation layer, and application layer. Session layer is the 5th layer...
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...assignment1 Frame relay migration to MPLS Frame relay | MPLS | Frame Relay is based on the PVC or Permanent Virtual Circuit. You access the network using a specialized piece of customer premises equipment called a FRAD or Frame Relay Access Device. Within the network frame routers are configured by the network operator to create your PVCs from a list of sources and destinations and your desired bandwidth or Committed Information Rate (CIR). | MPLS or Multi Protocol Label Switching is also a private network arrangement. It's designed to run on the newer IP based networks that are replacing traditional circuit switched or TDM (Time Division Multiplexing) networks. The multi-protocol aspect allows all sorts of traffic to be carried on the network simultaneously. What MPLS layers over the core IP network is a specialized label system. Each label specifies source and destination and quality of service. The labels work something like the virtual circuits of Frame Relay in that they identify where packets are coming from and where they are intended to go. | Benefits * Keeping cost of ownership and technology complexity low at point-of-sale and branch endpoints, ensuring fast service activation. * Deploy products to enable simultaneous delivery of private line, Frame Relay, and MPLS services during the transition phase to avoid service interruption. * Build MPLS-compatible traffic quality classification, performance, and quality standards into the Vanguard Networks'...
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...Protocol Paper NTC/362 Fundamentals of Networking Protocol Paper Introduction Switching, whether it is packet or circuit, is an essential portion of any network. By not using the right equipment, or using it properly, you can cause massive lag time or jitter within your own system. This will result in packet collision, loss of data, and could result in loss of business. Open Systems Interconnection Protocol Model In order for two computers to be able to interchange data and information, they first must establish communicate with each other. Protocols allow for this communication to take place (Goleniewski). The Open Systems Interconnection (OSI) Model gives a logical design that is used for communication between systems. The OSI Model is layered with seven subcomponents: Application (7), Presentation (6), Session (5), Transport (4), Network (3), Data Link (2) and Physical (1). Each one of these layers presents a collection of services. These services are provided to the layers that are above and below that specific layer. In addition to these, the OSI Model also details the transfer of computer packets using layer protocols (Goleniewski). The Application layer has the role of maintaining the exchange of information between a computer’s programs and services on the network. The Presentation layer makes it possible for software applications to read information by formatting it. Support for connections between sessions is handled through the Session layer. It...
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...how data moves through a system, advantages and disadvantages of circuit and packet switches. Considerations for performance, speed and throughput potential. The reliability and predictability of end-to-end transmission. The importance of the major protocols for circuit switching and packet switching. Considering these choices are a vital part of any network protocol. Open System Interconnection OSI or Open System Interconnection is how applications can communicate over a network by using a reference model. The reference model’s purpose is to make it to where venders and developers’ products can interoperate. “Developing OSI in 1983, was created and intended to be detailed specifications of actual interfaces (Rouse, 2014).” The OSI is a seven layer interface. Now this interface work backwards starting with layer seven the application layer. This layer is not the application itself more it’s the communication layer. It answers the question is there someone to talk to on the other end and can I talk to the other end right now. Layer six, the layer which represents the operation system converting data coming onto and out of the network from one format to another. Layer five encompasses the session layer, coordinates and terminates the conversations. Including authentication and reconnection after interruptions. Layer four is the transport layer managing the packetization of the data, delivering packets, and checking for errors once data arrives. Layer three, network layer handling...
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...IT 320 WAN Homework Unit 1 Vocabulary Exercise: Matching (Pg 3) Matching a) When referring to clocking, the CSU/DSU is this piece of equipment Data Circuit Terminating Equipment (DTE) b) The software used by a router Cisco IOS c) Dialup and ISDN are examples of these types of networks Circuit Switching d) Describes the timing between the router and the CSU/DSU Synchronous e) Lost when a device is powered down or rebooted Contents of RAM f) Wires or other media through which data is transmitted from one place to another Serial Link g) Connects LANs to WANs Interface h) The physical connection point on networking devices where signals enter and exit Router i) A smaller, more compact physical connection physical interface specification Smart serial interface j) A WAN link contracted for use by the customer Leased Line k) Frame relay and ATM are examples of these types of networks Packet Switching l) When referring to clocking the customer’s router , this piece of equipment is used Data Terminal Equipment (DTE) m) A communications link that is outside the normal IP network, like a console cable or a phone call between two modems and the aux port. Out of Band Management n) A network that spans a large geographic region WAN o) A telecommunications path that sends 1 bit at a time Serial Interface p) The router port that connects a WAN link Bus ...
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...The four major protocols for circuit switching and packet switching are as follows: • X.25 • Frame Relay • ATM or Asynchronous Transfer Mode protocol • TCP/IP X.25 is probably one of the very first of packet switching protocols. It performs really well, especially considering how long it has been around. X.25 uses a virtual circuit approach, mainly using POTS or plain old telephone service lines, which are different from lines such as ISDN. The POTS lines are analog copper lines, so they can experience a lot of errors. But, once the lines have been connected, X.25 connections are really reliable. It's quite an efficient way to send packets across various data networks, with the X.25 protocol redundant error checking at each of the nodes. Frame relay is different because it doesn't require the need for analog wires or overhead wires like X.25 does. But this means that Frame Relay doesn't have the added framing and processing that X.25 has that provide guaranteed data transfers. It also doesn't have link to link reliability. So if a frame is corrupted, it is discarded, which is different than TCP as it detects and recovers any and all discarded frames. Asynchronous Transfer Mode protocol is used with either a coaxial cable, twisted pair, or fiber. ATM also takes advantage of a 53-btye cell, having 48 application bytes and 5 bytes are allocated for the ATM headers. ATM shows a lot more enhancements over Frame Relay...
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...been plagued by simple voice communication issues such as dropped calls and network availability. When calls can be completed they are often hampered by quality of service issues that make the calls unintelligible. The purpose of the consultation is to rectify these voice quality issues by determining if they stem from network capacity and data transmission problems or if there exists a condition where there is improper coverage to service his well-established subscriber base. Analysis Circuit-Switched Transmission To better understand the concept of how mobile wireless voice works, it is necessary to have a comprehension of the differences between circuit-switched and packet-switched networks. The traditional method of routing phone calls on a public switched telephone network involves circuit- switching. Phone calls are routed or...
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...15) C 16) B, D 17) C 18) D 19) C, D 20) A, B Key Terms Switched circuit-A circuit by the phone company in reaction to signaling (the user tapping telephone keys or a modem sending in the same digits), with the telco tearing down the circuit when the user is finished. Dedicated circuit- An electric circuit created by a telco on behalf of a customer, with the circuit staying up all the time, dedicated for use by the one customer that ordered the circuit. Also known as a line, leased circuit, and point-to-point line. Circuit switching-The overall process by which a series of telco devices called circuit switches connect a circuit from one customer to the other, with the device’s logic taking incoming bits on one segment in the link and forwarding those bits out the matching outgoing segment, without storing bits. Packet switching-Process of forwarding customer data in a WAN by looking at the header of the messages sent into the WAN by the customer and making a per-messages decision as to where to forward each message. Leased line-A physical link between two locations, provided by a telco, that allows two-way communication between sites. Time-division multiplexing-A type of logic used by some networking devices, including circuit switches in the telco, in which the switch divides a faster line into time channels. T-carrier system- The name of the combination of different physical line standards (DS0, DS1, DS3, and...
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