Lecture 2 Slides PDF

COM204 Computer Networks Chapter 1 Fundamentals of Computer Networks Lecture Notes Prepared by Prof. Mahmoud Elmesalawy Electronics and Communication Engineering Department Faculty of Engineering Helwan University  Chapter...

COM204 Computer Networks Chapter 1 Fundamentals of Computer Networks Lecture Notes Prepared by Prof. Mahmoud Elmesalawy Electronics and Communication Engineering Department Faculty of Engineering Helwan University  Chapter (1): Fundamentals of Computer Networks 1.1 Introduction to data communications and Computer Networks 1.1.1 Components of Data Communication 1.1.2 Transmission Modes 1.1.3 Computer Network and Services 1.1.4 Clients and servers 1.1.5 Peer-to-Peer 1.2 Network Components 1.2.1 Network Devices 1.2.2 Network Media 1.2.3 Network Services 1.3 Network Topologies 1.3.1 Mesh Network Topology 1.3.2 Tree Network Topology 1.3.3 Bus Network Topology 1.3.4 Ring Network Topology 1.3.5 Star Network Topology 1.3.6 Hybrid Network Topology 1.3.7 Topology Diagrams  Chapter (1): Fundamentals of Computer Networks 1.4 Network Classifications 1.4.1 Personal Area Network (PAN) 1.4.2 Local Area Network (LAN) 1.4.3 Campus Area Network (CAN) 1.4.4 Metropolitan Area Network (MAN) 1.4.5 Wide Area Network(WAN) 1.5 Circuit Switched and Packet switched Networks 1.5.1 Broadcast and Switched Networks 1.5.2 Switched Communication Networks 1.6 Interconnection of Networks: The Internet 1.7 Converged Networks 1.1 Introduction to Data Communications and Computer Networks Data Communication is the exchange of data between two devices via some form of transmission medium as shown in Fig. 1.1. The fundamental problem of communication is that of reproducing at one point either exactly or approximately a message selected at another point. Fig. 1.1 Components of data communication. 1.1 Introduction to Data Communications and Computer Networks Five components of data communication as shown in Fig. 1.1. 1. Message is the data. 2. Sender is the device that send the message. 3. Receiver is the device that receive the message. 4.Transmission Medium is the physical path between sender and receiver. 5.Protocol is a set of rules that governs data communication. It represents an agreement between the communicating devices. Without a protocol, two devices may be connected but not communicating. Characteristics of Data Communication 1. Delivery: The system must deliver data to the correct destination. 2. Accuracy: Data delivered accurately, because altered data which left uncorrected are unusable. 3. Timeliness: The system must deliver data in timely manner without delay (real-time). 1.1 Introduction to Data Communications and Computer Networks 1.1.2 Transmission Modes in data communication 1. Simplex: one direction only, so always one side is a sender and another side is a receiver as in Fig. 1.2(a). Remote Control TV Receiver Monitor and Keyboard Fig. 1.2(a) Simplex transmission mode. 2. Half-Duplex: two-way alternate, so each side maybe sender or receiver but not at the same time. In different time Walki-Talki Fig. 1.2(b) Half-duplex transmission mode. 1.1 Introduction to Data Communications and Computer Networks 3. Full Duplex: two-way concurrent so each side can send and receive at same time as in Fig. 1.2(c). At same time Computer network At same time Mobile Network Fig. 1.2(c) Full duplex transmission mode. 1.1 Introduction to Data Communications and Computer Networks 1.1.3 Computer Network and Services A Network is a set of nodes connected together by communication link to share of resources and to transmit information. Node: Computer, Printer, Scanner, server, Copy machine, IP phone, etc. Information: Multimedia (text, voice, picture, etc). Resources: Printer, Scanner, Memory, Information, Network Bandwidth, Internet Services, Database, etc. Why do we need computer Networks? Need to communicate and share information among different devices. Direct connectivity between each and every device is not feasible. Direct connectivity between each and every device is not actually necessary.  1.1 Introduction to Data Communications and Computer Networks Network Services - Sharing (data, file, printer, application, resources). - Internet browsing. - Telephony. - Conferencing. - Database. - Backup. - Etc…….. Fig. 1.3 Example of Data sharing service (Email service). 1.1 Introduction to Data Communications and Computer Networks 1.1.4 Clients and Servers Servers are computers with software that enable them to provide information, like email or web pages, to other end devices on the network. Each service requires separate server software. Clients are computers with software installed that enable them to request and display the information obtained from the server. Web Client and Server: The Web Server runs web server software and clients use their browser software, such as Google chrome, Edge, Firfox, Windows Internet Explorer, to access web pages on the server. Email Client and Server: The Email Server runs email server software and clients use their mail client software, such as Microsoft Outlook, to access email on the server. File Client and Server: The File Server stores corporate and user files in a central location. The client devices access these files with client software such as Windows Explorer. 1.1 Introduction to Data Communications and Computer Networks 1.1.5 Peer-to-Peer Client and server software usually runs on separate computers, but it is also possible for one computer to carry out both roles at the same time. In small businesses and homes, many computers function as the servers and clients on the network. This type of network is called a peer-to-peer network. 1.2 Network Components There are three categories of network components: 1. Devices 2. Media 3.Services Fig. 1.4 Categories of network components. 1.2 Network Components 1.2.1 Devices 1. End Devices End device is either the source or destination of a message transmitted over the network. Some examples of end devices are: Computers (Desktop, laptops, servers) Network printers  VoIP phones Tele Presence endpoint  Security cameras Mobile handheld devices (such as smart phones, tablets, PDAs) Fig. 1.5(a) End devices. 1.2 Network Components 1.2.1 Devices 1. End Devices Network Interface Card (NIC): For Network Connectivity Wireless NIC: For WLAN (WiFi) Network Connectivity Fig. 1.5(b) Network Interface Cards. 1.2 Network Components 1.2.1 Devices 2. Intermediary Network Devices Intermediary devices connect the individual end devices to the network and can connect multiple individual networks to form an internetwork. Some examples of intermediary network devices are: Network Access Devices (LAN switches, access points and wireless routers) Internetworking Devices (routers) Security Devices (firewalls) Fig. 1.6(a) Network infrastructure devices. 1.2 Network Components 1.2.1 Devices 2. Intermediary Network Devices Repeater: Regenerates the signal Hub: For LAN implementation for network extension Ethernet Switch (Access and core switches): Bridge: For connecting different For Switched LAN implementation LANs Fig. 1.6(b) Network infrastructure devices.. 1.2 Network Components 1.2.1 Devices 2. Intermediary Network Devices Router: For LAN/WAN Internetworking Gateway: For different network internetworking DSL Router: For Internet Access WAN Switch: For WAN implementation Connection Fig. 1.6(c) Network infrastructure devices. 1.2 Network Components 1.2.2 Network Media Some examples of media are: Metallic wires cables - data is encoded into electrical impulses. Glass or plastic fibers (fiber optic cable) - data is encoded as pulses of light. Wireless transmission - data is encoded as electromagnetic waves. Fig. 1.7(a) Network media: Wired and wireless. 1.2 Network Components 1.2.3 Network Services Network services include many of the common network applications people use every day, like email hosting services and web hosting services. Processes provide the functionality that directs and moves the messages through the network. 1.3 Network Topologies 1.3.1 Mesh Network Topology All nodes connected to each other. Fig. 1.8 Mesh network topology. 1.3 Network Topologies 1.3.2 BUS Network Topology All nodes are connected to a single wire (the bus) that has two endpoints. Fig. 1.9 BUS network topology. 1.3.3 Star Network Topology All nodes are connected to a central point. Fig. 1.10 Star network topology. 1.3 Network Topologies 1.3.4 Tree Network Topology Most common due to simple establishment, easy network extension and more. Fig. 1.11 Tree network topology. 1.3.5 Ring Network Topology All nodes connected to a closed loop. Fig. 1.12 Ring network topology. 1.3 Network Topologies 1.3.6 Hybrid Network Topology Hybrid network topology includes different networks. Fig. 1.13 Hybrid network topology. 1.3 Network Topologies 1.3.7 Topology Diagrams Topology diagrams are mandatory for anyone working with a network. They provide a visual map of how the network is connected. There are two types of topology diagrams: Physical topology diagrams - Identify the physical location of intermediary devices and cable installation. Fig. 1.14(a). Physical Topology Diagram. 1.3 Network Topologies 1.3.7 Topology Diagrams Logical topology diagrams - Identify devices, ports, and addressing scheme. Fig. 1.14(b). Physical Topology Diagram. 1.4 Network Classifications Upon the scale (size) networks are Classified as:- 1. PAN (Personal Area Network). 2. LAN (Local Area Network). 3. CAN (Campus Area Network). 4. MAN (Metropolitan Area Network). 5. WAN (Wide Area Network). 1.5.1 Personal Area Network (PAN) 110 m PAN is a short-distance network design to individual user (person). PAN may contain:- printer, mobile, computer, wireless printers, PDA, etc. Components of PAN are connected together via Bluetooth, USB cable, IrDA (infrared), etc. as in Fig. 1.15. 1.4 Network Classifications 1.4.1 Personal Area Network (PAN) Wireless Printer IrDA Scanner Fig. 1.15 Personal Area Network. PDA 1.4 Network Classifications 1.4.2 Local Area Network (LAN) A network infrastructure that provides access to users and end devices in a small geographical area, which is typically an enterprise, home, or small business network owned and managed by an individual or IT department. Fig. 1.16(a) Local Area Network. 1.4 Network Classifications 1.4.2 Local Area Network (LAN) Floor 4 ……….. Floor 3 …….……….. Floor 2 Floor 1 Fig. 1.16(b) Local Area Network. 1.4 Network Classifications 1.4.3 Campus Area Network (CAN) A CAN is a group of interconnection LAN within limited geographical area. A CAN used in school campus, military base, university campus ,etc. Administration building University library IT faculty Fig. 1.17 Campus Area Network. 1.4 Network Classifications 1.4.4 Metropolitan Area Network (MAN) A network infrastructure that spans a physical area larger than a LAN but smaller than a WAN (e.g., a city). MANs are typically operated by a single entity such as a large organization. CAN 4 Connect LAN 1 different branch location in city LAN 3 LAN 2 Fig. 1.18 Metropolitan Area Network. 1.4 Network Classifications 1.4.5 Wide Area Network (WAN) A network infrastructure that provides access to other networks over a wide geographical area, which is typically owned and managed by a telecommunications service provider. Fig. 1.19 Wide Area Network. 1.4 Network Classifications WAN MAN CAN LAN PAN Fig. 1.20 Network Classification. 1.5 Circuit Switched and Packet Switched Networks Communication networks can be classified based on the way in which the nodes exchange information as shown in the following chart 1.5 Circuit Switched and Packet Switched Networks 1.5.1 Broadcast and switched networks 1. Broadcast Communication Networks Information transmitted by any node is received by every node in the network. Ex: Broadcast Ethernet, wireless LANs Need to coordinate the access to the shared medium (Media Access Control  MAC) 2. Switched Communication Networks Fig. 1.21(a) Broadcast Long distance transmission between stations network. (called “end devices”) is typically done over a network of switching nodes. Switching nodes do not concern with content of data. Their purpose is to provide a switching facility that will move the data from node to node until they reach their destination (the end device). A collection of nodes and connections forms a communications network. Ex: WANs (Telephony Network, Internet). Fig. 1.21(b) Switched network. 1.5 Circuit Switched and Packet Switched Networks 1.5.2 Switched Communication Networks 1. Circuit Switching In a circuit-switching network, a dedicated communications path is established between two stations through the nodes of the network. That path is a connected sequence of physical links between nodes, with a logical channel dedicated to the connection. Data generated by the source station are transmitted along the dedicated path. The most common example of circuit switching is the telephone network. Circuit switching is suitable for real-time services (Voice and video transmission) Three phases: 1. Circuit Establishment: allocates certain bandwidth and establish a path. 2. Data Transfer. 3. Circuit Termination If circuit not available: “Network Busy” Ex: Telephone networks Fig. 1.22(a) Circuit switching. 1.5 Circuit Switched and Packet Switched Networks 1.5.2 Switched Communication Networks 1. Circuit Switching Switch C Switch A Switch D Switch B Physical copper connection set up when call is made Switching offices Fig. 1.22(b) Circuit switching establishment. 1.5 Circuit Switched and Packet Switched Networks 1.5.2 Switched Communication Networks 1. Circuit Switching Switch A Switch B Switch C Switch D Tp Circuit 5Tp Establishment Tt Data Transfer Circuit Disconnect Time Time Time Time Time Time Fig. 1.22(c) Event timing in circuit switching. 1.5 Circuit Switched and Packet Switched Networks 1.5.2 Switched Communication Networks Problems of circuit switching Inefficiency – Channel capacity is dedicated for the whole duration of a connection. – For voice connections, the resulting circuit will enjoy a high percentage of utilization because most of the time one party or the other is talking. – For data transmission, much of the time the connection is idle (say: web browsing). Therefore capacity is wasted. – Example for data connection using circuit switching: Internet access through telephone line using modem. Delay – Long initial delay: circuit establishment takes time. Data rate is fixed – Both ends must operate at the same rate during the entire period of connection. Packet switching is designed to address these problems. 1.5 Circuit Switched and Packet Switched Networks 1.5.2 Switched Communication Networks 2. Packet Switching A packet-switching network uses a quite different approach, without need to dedicate transmission capacity along a path through the network. Rather, data is sent in a sequence of small chunks, called packets. Each packet is passed through the network from node to node along some path leading from source to destination. At each node, the entire packet is received, stored briefly, and then transmitted to the next node. Packet-switching networks are commonly used for terminal-to-computer and computer-to-computer communications. Fig. 1.23(a) Packet switching. 1.5 Circuit Switched and Packet Switched Networks 1.5.2 Switched Communication Networks 2. Packet Switching Router E Router C Router A Router D Router Congested Router B Routers Fig. 1.23(b) Packet switching example. 1.5 Circuit Switched and Packet Switched Networks 1.5.2 Switched Communication Networks 2.1 Datagram Packet Switching Each packet is treated independently, with no reference to packets that have gone before. – Each node chooses the next node on a packet’s path. Packets can take any possible route. Packets may arrive at the receiver out of order. Packets may go missing. It is up to the receiver to re-order packets and recover from missing packets. Each packet contains a portion of user data plus some control information (Routing/addressing information) Example: Internet Fig. 1.24 Datagram Switching. 1.5 Circuit Switched and Packet Switched Networks 1.5.2 Switched Communication Networks 2.2 Virtual Circuit Packet Switching A route between stations is set up prior to data transfer. All the data packets then follow the same route. Each packet contains a virtual circuit identifier (VCI) instead of destination address, and each node on the pre- established route knows where to forward such packets. But there is no dedicated resources reserved for the virtual circuit. Packets need to be stored-and- forwarded. Example: X.25, Frame Relay, ATM. Fig. 1.25 Virtual circuit Switching. 1.5 Circuit Switched and Packet Switched Networks 1.5.2 Switched Communication Networks Comparison Between Datagram & Circuit Switching 1.5 Circuit Switched and Packet Switched Networks 1.5.2 Switched Communication Networks Message vs Packet Switching Message Switching Packet Switching One single datagram Message chopped in small packets Each packet includes header (1.1) Message switching overhead lower than packet switching. But sometimes message switching not possible (e.g. for real time sources (1.2) such as voice) 1.5 Circuit Switched and Packet Switched Networks 1.5.3 Message/Packet Switching Delay Analysis In packet switching network there are delay time components which include: 1. Packet Transmission Time (Tt ). 2. Packet Propagation time (Tp). Refer to 3. Packet Processing time (Tprc).. Fig. 1.26 4. Packet Queuing time (Tq). The Packet Processing time (Tprc) and Packet Queuing time (Tq) are small so they can be neglected, and we will concentrate with Tt and Tp. Packet Transmission Time (Tt ) It is the time required to put all packet bits over the physical channel. It is dependent on the link transmission rate, C [bit/s or bps] and packet size, B [bit]. Tt is given by: Tt = B / C [sec] (1.3) Fig. 1.26 packet switching Example: If Transmission Rate is C = 1 Mbps and delay times. Packet Size is B = 8000 bits then Transmission Time is: Tt = B / C = 8000 / 1*106 = 8 ms 1.5 Circuit Switched and Packet Switched Networks 1.5.3 Message/Packet Switching Delay Analysis Packet Propagation Time (Tp ) It is the time it takes the electrical signals to travel from one machine to the other. It is dependent on the phase velocity of wave, vp on the medium and the distance between the two machines (link length), d. Tp is given by: Tp = d / vp [sec] (1.4) Example: Assume the phase velocity of the wave over cable is vp = 2.3*108 m/s and the distance between two machines is d = 1000 Km, then the Propagation Time is: Tp = d / vp = 1000 * 103 / (2.3*108) = 4.345 ms 1.6 Interconnection of Networks: The Internet The term internet (with a lower case “i") is used to describe multiple networks interconnected. Fig. 1.27 internetworks (internet). 1.6 Interconnection of Networks: The Internet (Continued) The term Internet (with a capital “I”) is used When referring to the global system of interconnected computer networks or the World Wide Web. Internet evolved from Advanced Research Projects Agency NET (ARPANET) in USA. Led to standardized TCP/IP protocols. The Internet is a worldwide collection of interconnected networks (internetworks or internet for short). The figure shows one way to view the Internet as a collection of interconnected LANs and WANs. The Internet is not owned by any individual or group. There are organizations that have been developed for the purpose of helping to maintain structure and standardization of Internet protocols and processes. These organizations include the Internet Engineering Task Force (IETF), Internet Corporation for Assigned Names and Numbers (ICANN), and the Internet Architecture Board (IAB), plus many others. Fig. 1.28 Internet: Collections of Interconnected LANs and WANs. 1.6 Interconnection of Networks: The Internet (Continued) Open circle = NAP which means Network Access Point Filled circle = POP which means Point Of Presence or the point at which two or more different networks or communication devices build a connection with each other. Fig. 1.29 Internet Architecture. 1.7 Converged Network 1.7.1 Multiple Networks Multiple Networks are running on multiple networks as shown in Fig. 1.27. Fig. 1.30 Multiple Networks. 1.7 Converged Network 1.7.2 Converging Networks Today, the separate data, telephone, and video networks are converging. Unlike dedicated networks, converged networks are capable of delivering data, voice, and video between many different types of devices over the same network infrastructure, as shown in the figure. This network infrastructure uses the same set of rules, agreements, and implementation standards as shown in Fig. 1.31. Fig. 1.31 Converged Data Networks: carry multiple services on one network.