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  • 1. Internet Architecture and Protocols Instructor: Engr. Musfara Farooqui University of Education Township Lahore
  • 2. Lecture # 01 Introduction and Basic Concepts University of Education Township Lahore 2
  • 3. Course Objectives  To understand the design philosophy of the Internet and its basic architectural components.  To provide in-depth knowledge of major Internet technologies.  To understand the components of Internet service provider and its role in Internet architecture.  To strengthen the concepts of TCP/IP Protocol Suite.  To provide comprehensive knowledge and implementation of routing protocols.  To realize the need of Quality of Service based communication and to understand various QoS techniques.  To introduce the basic concepts of real time communications. University of Education Township Lahore 3
  • 4. Lecture - Objectives  Introduction  What is the Internet?  Nuts and Bolts View  Service Oriented View  Network Edge  Network Core  Circuit Switched Networks  Packet Switched Networks  Datagram  Virtual Circuits  Network Access and Physical Media University of Education Township Lahore 4
  • 5. Lecture 1: What is the Internet?  A Nuts and Bolts Description  End systems  Communication Links, Bandwidth  Routers, Packet  ISPs  Protocols, TCP/IP  Internet Standards, RFCs  A service Description  Distributed Applications  Connection Oriented Reliable Service  Connectionless Unreliable Service  What is a protocol? University of Education Township Lahore 5
  • 6. Describing the Internet  Two ways to describe the Internet  Nuts and Bolts View The basic hardware and software components  Service Oriented View The networking infrastructure that provides services to distributed applications University of Education Township Lahore 6
  • 7. Nuts and Bolts View of the Internet  Hosts or End Systems  Computing Devices such as PCs, PDAs (Personal Digital Assistants), TVs, servers, mobile computers, automobiles, etc. connected to the Internet are called hosts or end systems University of Education Township Lahore 7
  • 8. Nuts and Bolts View of the Internet  Communication links  End systems are connected together by communication links.  Communication links are made up of different types of media, including twisted pair, coaxial cable, fiber optics, and radio spectrum.  Bandwidth  Different links can transmit data at different rates.  The link transmission rate is often called the bandwidth (i.e., the width of the band) of the link which is measured in bits per second (bps). University of Education Township Lahore 8
  • 9. Nuts and Bolts View of the Internet  Routers  End systems are not directly connected to each other via a single communication link.  They are indirectly connected to each through intermediate switching devices known as routers.  A router receives chunk of information from one of its incoming communication link and forwards it to one of its outgoing communication link. University of Education Township Lahore 9
  • 10. Nuts and Bolts View of the Internet  Packets  The chunk of information is called packet.  Route or Path  The path that the packet takes from the sending end system, through a series of communication links and routers, to the receiving end system is known as a route or path.  Packet switching  The Internet uses a technique known as packet switching that allows multiple communicating end systems to share a path, or parts of path at the same time. University of Education Township Lahore 10
  • 11. Nuts and Bolts View of the Internet  Internet Service Providers (ISPs)  End systems access the Internet through the Internet Service Providers (ISPs).  The different ISPs provide a variety of different types of network access to the end systems, including 56Kbps dial up modem access, cable modem or DSL, high speed LAN access, and wireless access. University of Education Township Lahore 11
  • 12. Nuts and Bolts View of the Internet  Protocols  End systems, routers, and other pieces of the Internet, run protocols that control the sending and receiving of information within the Internet.  TCP (Transmission Control Protocol) and IP (Internet protocol) are two of the most important protocols in the Internet.  The Internet’s principal protocols are collectively known as TCP/IP Protocol Suite. University of Education Township Lahore 12
  • 13. Nuts and Bolts View of the Internet  Intranets  There are many private networks, such as many corporate and government networks, whose hosts cannot exchange messages with hosts outside of the private network (unless the messages pass through so-called firewalls, which restrict the flow of messages to and from the network).  These private networks are often referred to as intranets, as they use the same types of hosts, routers, links, and protocols as the public Internet. University of Education Township Lahore 13
  • 14. Nuts and Bolts View of the Internet  Internet Standards  At the technical and development level, the Internet is made possible through creation, testing, and implementation of Internet Standards.  These standards are developed by Internet Engineering Task Force (IETF).  RFCs  The IETF standards documents are called RFCs (Request for comments).  RFCs started out as general request for comments (hence the name) to resolve architecture problems of the Internet.  They define protocols such as TCP, IP, HTTP, SMTP University of Education Township Lahore 14
  • 15. Some Pieces of the Internet router workstation server mobile local ISP regional ISP company network University of Education Township Lahore 15
  • 16. Lecture 2: Service Oriented View of the Internet  Distributed Applications  The Internet allows distributed applications running on its end systems to exchange data with each other.  These applications include remote login, electronic mail, web surfing, instant messaging, audio and video streaming, Internet telephony, distributed games, peer-topeer (P2P) file sharing, and much more.  Communication Services  Connection oriented reliable service  Connectionless unreliable service University of Education Township Lahore 16
  • 17. Service Oriented View of the Internet  Internet Provides two services to its distributed applications:  Connection Oriented Reliable Service • It guarantees that data transmitted from a sender to a receiver will eventually be delivered to the receiver in order and in its entirety.  Connectionless Unreliable Service • It does not make any guarantees about eventual delivery. – Note: Distributed applications makes use of one or the other (but not both) of these two services.  Thus, Internet is an infrastructure in which new applications are being constantly invented and deployed. University of Education Township Lahore 17
  • 18. Connection Oriented Service Reliable Data Transfer • Using acknowledgements & retransmissions Flow Control • sender won’t overwhelm receiver Congestion Control • senders “slow down sending rate” when network congested TCP • Applications using TCP are: – HTTP (Web), FTP (file transfer), Telnet (remote login), SMTP (email) University of Education Township Lahore 18
  • 19. Connectionless Service Unreliable Data Transfer • no flow control • no congestion control Fast • connectionless UDP • Applications using UDP are: – multimedia, videoconferencing, DNS, Internet telephony University of Education Township Lahore 19
  • 20. TCP vs. UDP TCP UDP  Reliable Protocol  Connection Oriented  Performs three ways handshake  Provision for error detection and retransmission  Most applications use TCP for reliable and guaranteed transmission  Unreliable Protocol  Connectionless  Much faster than TCP  No acknowledgement waits  No proper sequencing of data units  Suitable for applications where speed matters more than reliability University of Education Township Lahore 20
  • 21. What is a Protocol?  A Human Analogy  “Assalam u Alaikum”  “What’s the time?” • In human protocols specific messages are sent, and specific actions are taken in response to messages received, or other events.  Network protocols  All activity in the Internet that involves two or more communicating remote entities is governed by a protocol. University of Education Township Lahore 21
  • 22. What is a protocol? • A human protocol and a computer network protocol Hi TCP connection req Hi TCP connection response Got the time? 2:00 <file> time University of Education Township Lahore 22
  • 23. What is a Protocol?…  A Protocol is a set of rules and regulations that governs the exchange of information between two or more entities.  It takes two (or more) communicating entities running the same protocol in order to accomplish a task.  All communication activity in Internet governed by protocols.  A protocol defines the format, order of messages exchanged between two or more communicating entities, as well as the actions taken on the transmission and/or receipt of a message or other event. University of Education Township Lahore 23
  • 24. The Network Core  Mesh of interconnected Routers  The fundamental question: how is data transferred through network?  circuit switching • dedicated circuit per call: telephone net  packet-switching • data sent through net in discrete “chunks” University of Education Township Lahore 24
  • 25. Network Core  Long distance transmission is typically done over a network of switched nodes  Nodes not concerned with content of data  End devices are stations  Computer, terminal, phone, etc.  A collection of nodes and connections is a communications network  Data routed by being switched from node to node  Node to node links usually multiplexed University of Education Township Lahore 25
  • 26. Network Core: Circuit Switching  End-to-end resources reserved for “call”     link bandwidth, switch capacity dedicated resources: no sharing circuit-like (guaranteed) performance call setup required University of Education Township Lahore 26
  • 27. Network Core – Circuit Switching  Switched circuits allow data connections that can be initiated when needed and terminated when communication is complete  Circuit switched network - a network in which a dedicated circuit is established between sender and receiver and all data passes over this circuit.  The telephone system is a common example.  The connection is dedicated until one party or another terminates the connection. University of Education Township Lahore 27
  • 28. Circuit Switching University of Education Township Lahore 28
  • 29. Network Core – Circuit Switching  Dedicated communication path between two stations  Three phases (Establish, Transfer, Disconnect)  Inefficient (for data traffic)  Channel capacity dedicated for duration of connection  Much of the time a data connection is idle  If no data, capacity wasted  Set up (connection) takes time  Once connected, transfer is transparent  Circuit switching designed for voice  Constant Data rate (Both ends must operate at the same rate) University of Education Township Lahore 29
  • 30. Network Core - Circuit Switching  Multiplexing in Circuit Switched Networks  Multiplexing is a technique, in which a single transmission medium is being shared among multiple users.  Types of Multiplexing  Frequency Division Multiplexing FDM  Time Division Multiplexing TDM University of Education Township Lahore 30
  • 31. Circuit Switching: FDM and TDM University of Education Township Lahore 31
  • 32. Output Stream generated by a synchronous time division multiplexer University of Education Township Lahore 32
  • 33. Multiplexer transmission stream with one input device transmitting data. University of Education Township Lahore 33
  • 34. Two stations out of four transmitting via a statistical multiplexer University of Education Township Lahore 34
  • 35. Network Core: Packet Switching  Packet switched network  A network in which data is transmitted in the form of packets  Multiple users share network resources  No dedicated bandwidth is allocated      No resources are reserved, resources used as needed Each packet uses full link bandwidth Good for bursty traffic, simpler, no call setup Packets queued and transmitted as fast as possible Packets are accepted even when network is busy, which causes the delivery to slow down University of Education Township Lahore 35
  • 36. Packet Switching: Statistical Multiplexing 10 Mb/s Ethernet A B C statistical multiplexing 1.5 Mb/s queue of packets waiting for output link D E • Sequence of A & B packets does not have fixed pattern  statistical multiplexing University of Education Township Lahore 36
  • 37. Network Core: Packet Switching  The goal of packet switching is to move packets through routers from source to destination  Packets sent one at a time to the network  Two approaches are used:  Datagram Approach  Virtual Circuits Approach University of Education Township Lahore 37
  • 38. Packets Forwarding  Two broad classes of packet switched networks are:  Datagram Networks • Any network that forwards the packet according to the destination address is called a datagram network • The routers in the Internet forwards packets according to host destination addresses; hence the Internet is a datagram network.  Virtual Circuit Networks • Any network that forwards the packet according to the virtual circuit identifier is called a virtual circuit network • Examples are X.25, Frame Relay, ATM technologies University of Education Township Lahore 38
  • 39. Packet Switching - Datagram  Datagram Approach:  Each packet is treated independently  No reference to packets that have gone before  Each node chooses next node on path using destination address  Packets with same destination address may not follow same route  Packets may arrive out of sequence, may be lost  It is up to receiver to re-order packets and recover from lost packets  No Call setup  For an exchange of a few packets, datagram quicker  Analogy: driving, asking directions University of Education Township Lahore 39
  • 40. Packet Switching - Datagram  The Internet is a Datagram network  Datagram network is not either connection-oriented or connectionless.  Internet provides both connection-oriented (TCP) and connectionless services (UDP) to applications. University of Education Township Lahore 40
  • 41. Datagram Networks  A datagram network is not either a connectionless or a connection oriented network.  It can provide connectionless service to some of its applications and connection-oriented service to other applications.  Example  The Internet, which is a datagram network, provides both connectionless (UDP) and connection oriented (TCP) services to its applications  Networks with Virtual Circuits are, however, always connection-oriented. University of Education Township Lahore 41
  • 42. Packet Switching - Datagram University of Education Township Lahore 42
  • 43. Packet Switching: Datagram Approach University of Education Township Lahore 43
  • 44. Packet Switching – Virtual Circuits  Virtual Circuit Approach:  Virtual circuit packet switched network create a logical path through the subnet  Call request and call accept packets establish a virtual connection  Virtual route remains fixed through the call.  All packets from one connection follow this path.  Each packet contains a virtual circuit identifier instead of destination address to determines the next hop  Not a dedicated path  No routing decisions required for each packet University of Education Township Lahore 44
  • 45. Switching Technique – Virtual Circuit  Preplanned route established before packets sent  All packets follow same route  Similar to circuit in circuit-switching network  Hence virtual circuit  Each packet has virtual circuit identifier  Nodes on route know where to direct packets  No routing decisions  Not dedicated path, as in circuit switching  Packet still buffered at node and queued for output  Routing decision made on before that virtual circuit  Network may provide services related to virtual circuit  Sequencing and error control  Packets should transit more rapidly  If node fails, all virtual circuits through node lost University of Education Township Lahore 45
  • 46. Packet Switching: VC Approach University of Education Township Lahore 46
  • 47. Circuit Switching vs. Virtual Circuits CS VC  Path  A dedicated path is established between two devices for the duration of session.  Reserved Resources  The link (multiplexed / not multiplexed) that makes the path are dedicated, and cannot be used by other connections  constant data rates  Route  No dedicated path is established. Only a route is defined. Each switch creates an entry in its routing table for the duration of virtual circuit  Shared Links  The link that makes a route can be shard by other connections University of Education Township Lahore 47
  • 48. Network Taxonomy University of Education Township Lahore 48
  • 49. Network Access  Network Access:  The physical link that connects an end system to its Edge Router, which is the first router on a path from the end system to any other distant end system.  Classification of Network Access:  Residential Access • Connecting a home end system to an edge router • Dial-up modems, DSL, HFC system  Company Access • Switched Ethernet LANs  Mobile Access • Wireless LAN (802.11b) • Wide Area Wireless Access Networks (GPRS, 3G, WAP) • Note: these categories are not hard and fast University of Education Township Lahore 49
  • 50. Physical Media  Twisted Pair Cable – UTP Cat 5  Coaxial Cable – Baseband and Broadband Cable  Fiber Optics – Multimode and single mode  Terrestrial Radio Channels – Local Area Radio Channels (Wireless LANs) – Wide Area Radio Channels (WAP, I-mode, 3G)  Satellite Radio Channels – Geostationary Satellites (36000 km) – Low Altitude Satellites University of Education Township Lahore 50
  • 51. References  Computer Networking; A Top Down Approach Featuring the Internet – 3rd Edition: Chapter 1, Jim Kurose and Keith Ross  Data and Computer Communications – 7th Edition, William Stallings  Data Communications and Networking – 3rd Edition, Behrouz A. Forouzan  Data Communications and Computer Networks – Curt M. White  Computer Networks – 4th Edition, by Andrew S. Tanenbaum  Note: Slides are adapted from the companion web sites of referenced books. • University of Education Township Lahore 51