Download as PDF, PPTX
More Related Content
Similar to DCN 5th ed. slides ch01-Introduction.pdf
DCN 5th ed. slides ch01-Introduction.pdf
- 1. PART I: OVERVIEW INTRODUCTION Subject:Computer Networks Tutor: Bilal Munir Mughal 1 Ch-1
- 2. Content Outline DATACOMMUNICATIONS Components Data Representation Data Flow NETWORKS Network Criteria Physical Structures 2
- 3. Content Outline NETWORKTYPES Local Area Network Wide Area Network Switching The Internet Accessing the Internet STANDARDS AND ADMINISTRATION Internet Standards Internet Administration INTERNET HISTORY 3
- 4. Data Communications: Definition Data Communications: For data communications to occur, the communicating devices must be part of a communication system made up of a combination of hardware (physical equipment) and software (programs). 4 Transfer of data from one device to another via some form of transmission medium.
- 5. Data Communications: Motivations Efficient way to share resources Cost – less expensive Accessibility – easier Efficient way to exchange information Time – faster Size – bigger Correctness – more accurate 5
- 6. Data Communications: Effectiveness Theeffectiveness of a data communications system depends on four fundamental characteristics: 1. Delivery. The system must deliver data to the correct destination. Data must be received by the intended device or user and only by that device or user. 2. Accuracy. The system must deliver the data accurately. Data that have been altered in transmission and left uncorrected are unusable. 3. Timeliness. The system must deliver data in a timely manner. Data delivered late are useless. In the case of video and audio, timely delivery means delivering data as they are produced, in the same order that they are produced, and without significant delay (called real-time transmission). 4. Jitter. Jitter refers to the variation in the packet arrival time. It is the uneven delay in the delivery of audio or video packets. For example, let us assume that video packets are sent every 30 ms. If some of the packets arrive with 30-ms delay and others with 40-ms delay, an uneven quality in the video is the result. 6
- 7. Data Communications 7 Hi, howare you? 01010001 Hi, how are you? User Computer you? how are Hi, you? how are Hi, 01010001
- 8. Data Communications: Components 8 Hi,how are you? 5 Protocol 4 Medium 3 Receiver 2 Sender 1 Message
- 9. Data Representation Numbers 8/16/32 bit integers floating point Text ASCII, Unicode Images Bit patterns, Graphics formats JPG/GIF/etc Audio Samples of continuous signal Video Sequence of bitmap images 9 150 2 255
- 10. Direction of DataFlow Simplex: One direction only 10 Server Monitor data flow Keyboard data flow
- 11. Direction of DataFlow Half Duplex: Both directions, one at a time E.g., walkie-talkies 11 data flow at time 1 data flow at time 2
- 12. Direction of DataFlow Full Duplex: Both directions simultaneously E.g., telephone Can be emulated on a single communication link using various methods 12 data flow data flow
- 13. Networks Network: aset of devices connected by media links 13 Media Links Printer Workstation Laptop Scanner Server SD iMac
- 14. Networks: Criteria Anetwork must be able to meet a certain number of criteria. The most important of these are Performance Reliability Security 14
- 15. Networks: Criteria Performancecan be measured in many ways, including transit time and response time. Transit time is the amount of time required for a message to travel from one device to another. Response time is the elapsed time between an inquiry and a response. The performance of a network depends on the number of users type of transmission medium capabilities/efficiency of hardware, software 15
- 16. Networks: Criteria Performanceis often evaluated by two networking metrics: throughput and delay. We often need more throughput and less delay. However, these two criteria are often contradictory. If we try to send more data to the network, we may increase throughput but we increase the delay because of traffic congestion in the network. 16
- 17. Networks: Criteria Reliability In addition to accuracy of delivery, network reliability is measured by the frequency of failure, the time it takes a link to recover from a failure, and the network’s robustness in a catastrophe. Security Network security issues include protecting data from unauthorized access, protecting data from damage, and implementing policies and procedures for recovery from breaches and data losses. 17
- 18. Physical Structures: Typesof Connections Point-to-point Multipoint (multidrop) 18
- 19. Point-To-Point Connection 19 A point-to-pointconnection provides a dedicated link between two devices.
- 20. Multipoint Connection 20 Wireless A multipoint(also called multidrop) connection is one in which more than two specific devices share a single link.
- 21. Topology Topology: physicalor logical arrangement of devices Mesh Star Bus Ring Hybrid 21
- 22. Fully Connected MeshTopology 22 A C B D
- 23. Fully Connected MeshTopology Pros: Dedicated links Robustness Privacy Easy to identify fault Cons: A lot of cabling A lot of I/O ports Difficult to move 23 Number of physical links n (n – 1) / 2 in duplex-mode A C B D
- 24. Star Topology 24 Hub A D BC Drop Drop
- 25.
- 26.
- 27. Star Topology Pros: One I/O port per device Little cabling Easy to install Robustness Easy to identify fault Cons: Single point of failure More cabling still required 27 Hub Number of physical links n where n = number of nodes
- 28.
- 29.
- 30.
- 31. Bus Topology Pros: Little cabling Easy to install Cons: Difficult to modify Difficult to isolate fault Break in the bus cable stops all transmission 31 Number of physical links n + 1(backbone) where n = number of nodes
- 32.
- 33.
- 34. Ring Topology Pros: Easy to install Easy to identify fault Cons: Delay in large ring Break in the ring stops all transmission 34 Number of physical links n where n = number of nodes
- 35. Hybrid Topologies 35 ACT ACT 10M100M 1 23 4 13 14 15 16 5 6 7 8 17 18 19 20 9 10 11 12 21 22 23 24 UPLINK 1 2 3 4 5 6 7 8 9 101112 131415161718192021222324 COL COL PWR SWITCH ACT ACT 10M100M 1 2 3 4 13 14 15 16 5 6 7 8 17 18 19 20 9 10 11 12 21 22 23 24 UPLINK 1 2 3 4 5 6 7 8 9101112 131415161718192021222324 COL COL PWR SWITCH
- 36. Network Types LocalArea Network (LAN) Wide Area Network (WAN) 36
- 37. Local Area Networks Network in a small area e.g. single office, building, or campus 37
- 38. Wide Area Networks Network providing long-distance communication over a country, a continent, the whole world or beyond 38
- 39. Wide Area Networks Distinct examples of WANs today: point-to-point WANs and switched WANs. Point-to-Point WAN Switched WAN 39
- 40.
- 41. Network of Networks 42 CompanyA Company D Network Interface Card (NIC) Company B Company C
- 42. Internetworking How toallow devices from different standards to communicate Gateways/routers – devices capable of communicating in several standards These become "network of networks" 43
- 43. Internetworks Two ormore connected networks become an internetwork, or internet Example: The Internet 44 Network1 Network2 Gateway Network3
- 44. The Internet Thelargest internetwork (network of networks) in the world Devices communicating with TCP/IP protocol suite 45
- 45. Accessing The Internet Using Telephone Networks Dial-up service DSL Service Using Cable Networks Using Wireless Networks Direct Connection to the Internet 46
- 46. Internet Standards AnInternet standard is a thoroughly tested specification that is useful to and adhered to by those who work with the Internet. It is a formalized regulation that must be followed. 47
- 47. Internet Standards Thereis a strict procedure by which a specification attains Internet standard status. A specification begins as an Internet draft. An Internet draft is a working document (a work in progress) with no official status and a six-month lifetime. Upon recommendation from the Internet authorities, a draft may be published as a Request for Comments (RFC). Each RFC is edited, assigned a number, and made available to all interested parties. RFCs go through maturity levels and are categorized according to their requirement level. 48
- 48. Internet Standards: RFCMaturity Levels Maturity Levels An RFC, during its lifetime, falls into one of six maturity levels: 49
- 49. Internet Standards: RFCMaturity Levels Proposed Standard. A proposed standard is a specification that is stable, well understood, and of sufficient interest to the Internet community. At this level, the specification is usually tested and implemented by several different groups. Draft Standard. A proposed standard is elevated to draft standard status after at least two successful independent and interoperable implementations. Barring difficulties, a draft standard, with modifications if specific problems are encountered, normally becomes an Internet standard. 50
- 50. Internet Standards: RFCMaturity Levels Internet Standard. A draft standard reaches Internet standard status after demonstrations of successful implementation. Historic. The historic RFCs are significant from a historical perspective. They either have been superseded by later specifications or have never passed the necessary maturity levels to become an Internet standard. 51
- 51. Internet Standards: RFCMaturity Levels Experimental. An RFC classified as experimental describes work related to an experimental situation that does not affect the operation of the Internet. Such an RFC should not be implemented in any functional Internet service. Informational. An RFC classified as informational contains general, historical, or tutorial information related to the Internet. It is usually written by someone in a non-Internet organization, such as a vendor. 52
- 52. Internet Standards: RFC RequirementLevels RFCs are classified into five requirement levels Required. An RFC is labeled required if it must be implemented by all Internet systems to achieve minimum conformance. For example, IP and ICMP (Chapter 19) are required protocols. Recommended. An RFC labeled recommended is not required for minimum conformance; it is recommended because of its usefulness. For example, FTP (Chapter 26) and TELNET (Chapter 26) are recommended protocols. 53
- 53. Internet Standards: RFC RequirementLevels Elective. An RFC labeled elective is not required and not recommended. However, a system can use it for its own benefit. Limited Use. An RFC labeled limited use should be used only in limited situations. Most of the experimental RFCs fall under this category. Not Recommended. An RFC labeled not recommended is inappropriate for general use. Normally a historic (deprecated) RFC may fall under this category. 54
- 54. Internet Administration AppendixG gives the addresses, e-mail addresses, and telephone numbers for some of groups involved in growth and development of the internet. 55 Figure 1.17 shows general organization of Internet administration.
- 55. Internet Administration TheInternet Society (ISOC) is an international, nonprofit organization formed in 1992 to provide support for the Internet standards process. ISOC accomplishes this through maintaining and supporting other Internet administrative bodies such as IAB, IETF, IRTF, and IANA. ISOC also promotes research and other scholarly activities relating to the Internet 56
- 56. Internet Administration TheInternet Architecture Board (IAB) is the technical advisor to the ISOC. The main purposes of the IAB are to oversee the continuing development of the TCP/IP Protocol Suite and to serve in a technical advisory capacity to research members of the Internet community. IAB accomplishes this through its two primary components, the Internet Engineering Task Force (IETF) and the Internet Research Task Force (IRTF). Another responsibility of the IAB is the editorial management of the RFCs, described earlier. IAB is also the external liaison between the Internet and other standards organizations and forums. 57
- 57. Internet Administration TheInternet Engineering Task Force (IETF) is a forum of working groups managed by the Internet Engineering Steering Group (IESG). IETF is responsible for identifying operational problems and proposing solutions to these problems. IETF also develops and reviews specifications intended as Internet standards. The working groups are collected into areas, and each area concentrates on a specific topic. Currently nine areas have been defined. The areas include applications, protocols, routing, network management, IP next generation (IPng), and security. 58
- 58. Internet Administration TheInternet Research Task Force (IRTF) is a forum of working groups managed by the Internet Research Steering Group (IRSG). IRTF focuses on long-term research topics related to Internet protocols, applications, architecture, and technology. 59
- 59. INTERNET HISTORY Checkyour textbook for reference. 60
- 60.