FULL UNIT 1 CSE 306.pdf

Introduction  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 device...

Introduction  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 or may be wireless.  Effectiveness of Data Communication Four Fundamental Characteristics Delivery Accuracy Timeliness - -real time Jitter Components of a Data Communication System Continue… Five Components: Message- Text, Number, Image, Audio, Video Sender Receiver Transmission Medium Protocol Data flow (Simplex, Half-duplex, and Full-duplex  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.  Network Criteria Performance – Depends on Network Elements- Transmit time, Response Time, Number of users, type of transmission medium, hardware, software. – Measured in terms of Delay and Throughput Reliability – Failure rate of network components. – Time to recover from a failure. – Measured in terms of availability/robustness Security – Data protection against corruption/loss of data due to: – Errors – Malicious users/ Unauthorized access.  Physical Structures Type of Connection – Point to Point - single transmitter and receiver – Multipoint - multiple recipients of single transmission Physical Topology – Connection of devices – Type of transmission - unicast, mulitcast, broadcast Types of connections: point-to-point and multipoint  Uses of Computer Network Business Applications Home Applications Mobile Users Social Issues  Business Applications Resource sharing such as printers and storage devices Exchange of information by means of e-Mails and FTP Business Applications (1) A network with two clients and one server  Business Applications (2) The client-server model involves requests and replies  Home Applications (1) In a peer-to-peer system there are no fixed clients and servers. Home Applications (2) Some forms of e-commerce  Mobile Users Combinations of wireless networks and mobile computing  Social Issues Network neutrality Digital Millennium Copyright Act Profiling users Phishing  PROTOCOLS A protocol is synonymous with rule. It consists of a set of rules that govern data communications. It determines what is communicated, how it is communicated and when it is communicated. The key elements of a protocol are – Syntax – Semantics – Timing  Elements of a Protocol Syntax – Structure or format of the data – Indicates how to read the bits - field delineation Semantics – Interprets the meaning of the bits – Knows which fields define what action Timing – When data should be sent and what – Speed at which data should be sent or speed at which it is being received.  Types of Network Wired Networks Mobile Networks - high bandwidth - low bandwidth - low bandwidth variability - high bandwidth variability - can listen on wire - hidden terminal problem - high power machines - low power machines - high resource machines - low resource machines - low delay - higher delay - connected operation - disconnected operation -No Mobility. Mobility. The End  Network Software Architecture and its Layers and Protocols CSE306  Network Software Protocol Hierarchies Design Issues for the Layers Connection-Oriented and Connectionless Services Service Primitives The Relationship of Services to Protocols  Network Software Protocol Hierarchies Layers, protocols, and interfaces- Network Architecture  A protocol is an agreement between the communicating parties on how communication is to proceed. The entities comprising the corresponding layers on different machines are called peers. The peers may be software processes, hardware devices, or even human beings. In other words, it is the peers that communicate by using the protocol to talk to each other. A list of the protocols used by a certain system, one protocol per layer, is called a protocol stack.  Protocol Hierarchies (2) The philosopher-translator-secretary architecture.  Protocol Hierarchies (3) Example information flow supporting virtual communication in layer 5.  Design Issues for the Layers Addressing or naming Error Control Flow Control---Congestion Statistical Multiplexing Routing Scalable QoS---real time Reliability Security  Connection-Oriented and Connectionless Services A circuit is another name for a connection with associated resources, such as a fixed bandwidth. This dates from the telephone network in which a circuit was a path over copper wire that carried a phone conversation. In contrast to connection-oriented service, connectionless service is modeled after the postal system. Each message (letter) carries the full destination address, and each one is routed through the intermediate nodes inside the system independent of all the subsequent messages. Store or forward switching Cut through switching  Each kind of service can further be characterized by its reliability. Some services are reliable in the sense that they never lose data. Usually, a reliable service is implemented by having the receiver acknowledge the receipt of each message so the sender is sure that it arrived. Reliable connection-oriented service has two minor variations: message sequences and byte streams. The acknowledgement process introduces overhead and delays, which are often worth it but are sometimes undesirable. One such application is digitized voice traffic for voice over IP. Unreliable (meaning not acknowledged) connectionless service is often called datagram service. Connection-Oriented and Connectionless Services Six different types of service.  Service Primitives Five service primitives for implementing a simple connection-oriented service.  Service Primitives (2) Packets sent in a simple client-server interaction on a connection-oriented network.  Services to Protocols Relationship The relationship between a service and a protocol. Network Hardware and its Topologies CSE306  Categories of Networks Personal area networks Local Area networks Metropolitan Area networks Wide Area networks Wireless Networks Home Networks Internetworks- The Internet Personal Area Network Bluetooth PAN configuration  Local Area Networks (LANs) – Short distances – Designed to provide local interconnectivity Wireless and wired LANs. (a) 802.11. (b) Switched Ethernet. Isolated LAN connecting 12 computers to a hub in a closet  Wide Area Networks (WANs) – Long distances – Provide connectivity over large areas WANs: a switched WAN and a point-to-point WAN A heterogeneous network made of four WANs and two LAN 1.8  Metropolitan Area Networks (MANs) Provide connectivity over areas such as a city, a campus A metropolitan area network based on cable TV or telephone cable using DSL Wireless Networks (a) Bluetooth configuration (b) Wireless LAN  Wireless Networks (a) Individual mobile computers (b) A flying LAN  Home Network Categories Computers (desktop PC, PDA, shared peripherals Entertainment (TV, DVD, VCR, camera, stereo, MP3) Telecomm (telephone, cell phone, intercom, fax) Appliances (microwave, fridge, clock, furnace, airco) Telemetry (utility meter, burglar alarm, babycam).  THE INTERNET Inter connection of two or more networks become an 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. Hierarchical organization of the Internet  Broadcast Networks Classification of interconnected processors by scale.  Network Topology The topology of a network defines how the nodes of a network are connected. The shape of the cabling layout used to link devices is called the physical topology of the network. The logical topology, in contrast, is the way that the signals act on the network media, or the way that the data passes through the network from one device to the next without regard to the physical interconnection of the devices. Categories of Physical Topology  Mesh Topology Here every device has a point to point link to every other device. Node 1 node must be connected with n-1 nodes. A fully connected mesh can have n(n-1)/2 physical channels to link n devices. It must have n-1 I/O ports. A fully connected mesh topology (five devices) 1.19  Advantages of Mesh 1. They use dedicated links so each link can only carry its own data load. So traffic problem can be avoided. 2. It is robust. If any one link get damaged it cannot affect others. 3. It gives privacy and security.(Message travels along a dedicated link) 4. Fault identification and fault isolation are easy.  Disadvantages of Mesh 1. The amount of cabling and the number of I/O ports required are very large. Since every device is connected to each devices through dedicated links. 2. The sheer bulk of wiring is larger then the available space. 3. Hardware required to connected each device is highly expensive.  Applications of Mesh 1. Telephone Regional office. 2. WAN.(Wide Area Network).  Star Topology Here each device has a dedicated point-to-point link to the central controller called “Hub”(Act as a Exchange). There is no direct traffic between devices. The transmission are occurred only through the central “hub”. When device 1 wants to send data to device 2; First sends the data to hub. Which then relays the data to the other connected device. Star Topology  Advantages of Star Topology 1. Less expensive then mesh since each device is connected only to the hub. 2. Installation and configuration are easy. 3. Less cabling is need then mesh. 4. Robustness.(if one link fails, only that links is affected. All other links remain active) 5. Easy to fault identification & to remove parts. 6. No distruptions to the network then connecting(or) removing devices.  Disadvantages of Star Topology 1. Even it requires less cabling then mesh when compared with other topologies it still large.(Ring or bus). 2. Dependency(whole n/w dependent on one single point(hub). When it goes down. The whole system is dead.  Applications of Star Topology Star topology used in Local Area Networks(LANs). High speed LAN often used STAR.  Bus Topology A bus topology is multipoint. Here one long cable act as a backbone to link all the devices are connected to the backbone by drop lines and taps. Drop line- is the connection b/w the devices and the cable. Tap- is the splitter that cut the main link. This allows only one device to transmit at a time. Bus Topology  When a device sends a message, it is broadcast down on the cable in both directions. Terminators at the end of the cable prevent the signal from reflecting back to the sender. All devices on the cable constantly monitor for messages meant to them. When a device detects a message meant for it, it reads the message from the cable and the other devices will ignore it. Since all devices are sharing the same cable, some form of control is needed to make sure which device will transmit when, otherwise there will be a collision.  Advantages of Bus Topology 1. Ease of installation. 2. Less cabling. 3. less expensive.  Disadvantages of Bus Topology 1. Difficult reconfiguration and fault isolation. 2. Difficult to add new devices. 3. Signal reflection at top can degradation in quality. 4. If any fault in backbone can stops all transmission.  Applications of Bus Topology Most computer motherboard.  Ring Topology Here each device has a dedicated connection with two devices on either side. The signal is passed in one direction from device to device until it reaches the destination and each device have repeater. When one device received signals instead of intended another device, its repeater then regenerates the data and passes them along. To add or delete a device requires changing only two connections. Ring Topology  Ring Topology Advantages: 1. Easy to install. 2. Easy to reconfigure. 3. Fault identification is easy. Disadvantages: 1. Unidirectional traffic. 2. Break in a single ring can break entire network.  Ring Topology Applications: Ring topologies are found in some office buildings or school campuses. Today high speed LANs made this topology less popular.  Tree Topology Alternatively referred to as a star bus topology. Tree topology is one of the most common network setups that is similar to a bus topology and a star topology. A tree topology connects multiple star networks to other star networks. Below is a visual example of a simple computer setup on a network using the star topology.  Hybrid Topology A network which contain all type of physical structure and connected under a single backbone channel. Hybrid Topology  Considerations for Choosing Network Topology Money-Bus n/w may be the least expensive way to install a n/w. Length-of cable needed- the linear bus n/w uses shorter lengths of cable. Future growth-with star topology, expending a n/w is easily done by adding another devices. Cable type-most common used cable in commercial organization is twisted pair. Which is often used with star topologies.  Full mesh topology is theoretically the best since every device is connected to every other device.(thus maximizing speed and security. however, it quite expensive to install) Next best would be tree topology , which is basically a connection of star.  Backbone Networks: Serial Backbone Daisy chain: linked series of devices – Hubs and switches often connected in daisy chain to extend a network Hubs, gateways, routers, switches, and bridges can form part of backbone Extent to which hubs can be connected is limited Connecting devices  Repeater or hub A repeater forwards every bit; it has no filtering capability. A router is a three-layer (physical, data link, and network) device. A repeater or a bridge connects segments of a LAN. A router connects independent LANs or WANs to create an internetwork (internet). Routing example  Hub Broadcast More collision Connect same networking device  Switch Switch is intelligent device Learning the address Forwarding Work on mac address  Router Connect different networks Routing  OSI Model and TCP/IP protocol suite) CSE306 Tasks involved in sending a letter  THE OSI MODEL Established in 1947, the International Standards Organization (ISO) is a multinational body dedicated to worldwide agreement on international standards. An ISO standard that covers all aspects of network communications is the Open Systems Interconnection (OSI) model. It was first introduced in the late 1970s. Topics discussed in this section: Layered Architecture Peer-to-Peer Processes Encapsulation ISO is the organization. OSI is the model. Seven layers of the OSI model The interaction between layers in the OSI model An exchange using the OSI model  LAYERS IN THE OSI MODEL In this section we briefly describe the functions of each layer in the OSI model. Topics discussed in this section: Physical Layer Data Link Layer Network Layer Transport Layer Session Layer Presentation Layer Application Layer Physical layer The physical layer is responsible for movements of individual bits from one hop (node) to the next.  Physical layer Type of transmission media Representation of bits Data rate Synchronization of bits Line Configuration Topology Transmission mode Data link layer The data link layer is responsible for moving frames from one hop (node) to the next.  Data link layer Framing Physical addressing Flow control Error control Access control Hop-to-hop delivery Network layer The network layer is responsible for the delivery of individual packets from the source host to the destination host.  Network layer Logical addressing Routing Source-to-destination delivery Transport layer The transport layer is responsible for the delivery of a message from one process to another.  Transport layer Service-point addressing Segmentation and reassembly Connection control Flow control Error control Reliable process-to-process delivery of a message Session layer The session layer is responsible for dialog control and synchronization.  Session layer Dialog control (turn to transmit) Synchronization (introducing check point) Presentation layer The presentation layer is responsible for translation, compression, and encryption.  Presentation layer Translation Encryption Compression Application layer The application layer is responsible for providing services to the user.  Application layer Network Virtual Terminal File transfer, access, and management. Mail services Directory Services Summary of layers  TCP/IP PROTOCOL SUITE The layers in the TCP/IP protocol suite do not exactly match those in the OSI model. The original TCP/IP protocol suite was defined as having four layers: host-to-network, internet, transport, and application. However, when TCP/IP is compared to OSI, we can say that the TCP/IP protocol suite is made of five layers: physical, data link, network, transport, and application. TCP/IP and OSI model  ADDRESSING Four levels of addresses are used in an internet employing the TCP/IP protocols: physical, logical, port, and specific. Physical Addresses Logical Addresses Port Addresses Specific Addresses Addresses in TCP/IP Relationship of layers and addresses in TCP/IP Comparison of the OSI and TCP/IP Reference Models  Functionality of the layers is roughly similar Concepts central to OSI model Services : The service definition tells what the layer does, not how entities above it access it. It defines the layer's semantics. Interfaces : tells the processes above it how to access it. It specifies what the parameters are and what results to expect Protocols: the layer's own business.  Comparison of the OSI and TCP/IP Reference Models  OSI reference model was devised before the corresponding protocols were invented. This ordering means that the model was not biased toward one particular set of protocols  In TCP/IP, the protocols came first, and the model was really just a description of the existing protocols  Number of layers: the OSI model has seven layers and the TCP/IP has four layers.  The TCP/IP model has only one mode in the network layer (connectionless) but supports both modes in the transport layer.