Computer Network Systems I Lecture 1 - Introduction PDF

Computer Network Systems I Dr. Aymen J. Salman Department of Computer Engineering College of Engineering Al-Nahrain University [email protected] 1  Textbook...

Computer Network Systems I Dr. Aymen J. Salman Department of Computer Engineering College of Engineering Al-Nahrain University [email protected] 1  Textbook Data Communications and Networking, by Behrouze Fpurozan, 6th Edition, 2022 Computer Networks: A systems approach, by Peterson and Davie, 6th Edition, 2021 References Computer Networks, 5th Edition by Andrew Tanenbaum, 2011 Computer Networking: A Top Down Approach, 6th Edition by Kurose and Ross 2 1.3 1.4 1.5 1.6  Lecture 1 Introduction 7  1-1 DATA COMMUNICATIONS The term telecommunication means communication at a distance. The word data refers to information presented in whatever form is agreed upon by the parties creating and using the data. Data communications are the exchange of data between two devices via some form of transmission medium such as a wire cable. 1.8  Figure 1.1 Components of a data communication system 1.9  Figure 1.2 Data flow (simplex, half-duplex, and full-duplex) 1.10  1-2 NETWORKS A network is a set of devices (often referred to as nodes) connected by communication links. A node can be a computer, printer, or any other device capable of sending and/or receiving data generated by other nodes on the network. A link can be a cable, air, optical fiber, or any medium which can transport a signal carrying information. 1.11  Physical Structures n Type of Connection n Point to Point - single transmitter and receiver n Multipoint - multiple recipients of single transmission n Physical Topology n Connection of devices n Type of transmission - unicast, mulitcast, broadcast 1.12  Types of connections n Point to point n A dedicated link is provided between two devices n Multipoint n More than two specific devices share a single link 1.13  Physical Topology 1.14  MESH Topology n Every device has a dedicated point-to-point link to every other device n Dedicated n Link carries traffic only between the two devices it connects n A fully connected mesh network has n(n-1)/2 physical channels to link n devices n Every device on the network must have n-1 input/output (I/O) ports n Advantage n Less traffic, robust, secure, easy to maintain n Disadvantage n Need more resources (cable and ports), expensive n(n-1)/2 physical duplex links 1.15  STAR Topology n Each device has a dedicated point-to-point link only to a central controller, usually called a hub. n No direct traffic and link between devices n Advantages n Less expensive n Easy to install and reconfigure n Robustness n Disadvantage n Single point of failure 1.16  BUS Topology n A multipoint topology n All devices are linked through a backbone cable n Nodes are connected to the bus cable by drop lines and taps. n Dropline n A connection running between the device and the main cable n Tap n A connector that either splices into the main cable or punctures the sheathing of a cable to create contact with the metallic core n Advantage: n Ease of installation § Disadvantages: n Difficult reconnection and fault isolation n A broken or faulty bus cable stops all transmission 1.17  RING Topology n Each device is dedicated point-to-point connection only with the two devices on either side of it n A signal is passed along the ring in the direction, from device to device, until it reaches its destination n Each device in the ring incorporates a repeater n Advantages n Relatively easy to install and reconfigure n Fault isolation is simplified n Disadvantage n Unidirectional traffic 1.18  Tree Topology Tree topologies integrate multiple topologies together Example: Tree topology integrates multiple star topologies together onto a bus n Advantages: n Point-to-point wiring for individual segments. n Supported by several hardware and software vendors. n Disadvantages: n The overall length of each segment is limited by the type of cabling used. n If the backbone line breaks, the entire segment goes down. n More difficult to configure and wire than other topologies. 1.19  A hybrid topology: a star backbone with three bus networks 1.20  Categories of Networks n Local Area Networks (LANs) n Short distances n Designed to provide local interconnectivity n Metropolitan Area Networks (MANs) n Provide connectivity over areas such as a city, a campus n Wide Area Networks (WANs) n Long distances n Provide connectivity over large areas 1.21 1.22  WANs: a switched WAN and a point-to-point WAN 1.23  Interconnection of Networks: internet / internetwork 1.24  Internet vs internet (internetwork) q The internet is an interconnected network or network of networks q The Internet is a global network of billions of computers and other electronic devices. With the Internet, it’s possible to access almost any information, communicate with anyone else in the world, and do much more. You can do all this by connecting a computer to the Internet, also called going online. Hence, the Internet is an internet, but the reverse does not apply 1.25  1-3 THE INTERNET The Internet has revolutionized many aspects of our daily lives. It has affected the way we do business as well as the way we spend our leisure time. The Internet is a communication system that has brought a wealth of information to our fingertips and organized it for our use. Brief History 1967 ARPANET is the first Computer Network by DoD 1967 ACM (Association for Computing Machinery) 1972 TCP (Transmission Control Protocol) ISPs (Internet Service Provider) 1.26  ARPANET 1.27  Hierarchical organization of the Internet 1.28  Hierarchical organization of the Internet Ø Tier-1 ISP: These ISPs are at the top of the hierarchy and they have a global reach they do not pay for any internet traffic through their network instead lower-tier ISPs have to pay a cost for passing their traffic from one geolocation to another which is not under the reach of that ISPs. Generally, ISPs at the same level connect to each other and allow free traffic passes to each other. Such ISPs are called peers. They build infrastructure, such as the Atlantic Internet sea cables, to provide traffic to all other Internet service providers, not to end users. Such as Cogent Communications, Hibernia Networks, AT&T Ø Tier-2 ISP: These ISPs are service providers who connect between tier 1 and tier 3 ISPs. They have regional or country reach and they behave just like Tier-1 ISPs for Tier-3 ISPs. Such as Vodafone, Easynet, BT Ø Tier-3 ISP: These ISPs are closest to the end users and help them to connect to the internet by charging some money. These ISPs work on a purchasing model. These ISPs have to pay some cost to Tier-2 ISPs based on traffic generated. Such as Earthlink, HalaSat 1.29  ITPC v ITPC is an Iraqi Telecommunications and Post Company. v ITPC Network is the Optical Fiber Transmission Backbone in Iraq 1.30  Iraq Submarine Cables 1.31  1-4 PROTOCOLS A protocol is synonymous with the rule. It consists of a set of rules that govern data communications. It determines: what is communicated how it is communicated when it is communicated. The key elements of a protocol are syntax, semantics, and timing 1.32  Protocols vs Standards Protocol refers to a set of rules and conventions that govern how data is transmitted Standard is a formal document that specifies the details of how a protocol or technology should work. Standards are often developed and maintained by standards organizations, industry consortia, or government bodies. De facto → by fact (not approved as a standard) Ethernet HTTP (Hypertext Transport Protocol) BGP (Border Gateway Protocol) De jure → by Law (approved) TCP/IP (Transmission Control Protocol/Internet Protocol) is managed by Internet Engineering Task Force (IETF) IEEE 802.11 (Wi-Fi) maintained by the Institute of Electrical and Electronics Engineers (IEEE) DNS (Domain Name System) is managed by Internet Engineering Task Force (IETF) 1.33  Standards Bodies n Internet Engineering Task Force n Internet standards development n Request for Comments (RFCs): www.ietf.org n International Telecommunications Union n International telecom standards n IEEE 802 Committee n Local area and metropolitan area network standards 1.34  IEEE Network Standardization The IEEE 802 series standards The important ones are marked with *. The ones marked with ↓ are hibernating. The one marked with t gave up and disbanded itself.  Units Review Take care of “B” and “b”, “B” means byte, while “b” stands bit. E.g., 1 KB/s = 8 Kb/s. B/s = Bps, b/s = bps. 1K = 210 ≠ 103 ≈ 1,000 1K = 210; 1M = 220; 1G = 230 …