Data Communication Part 1 PDF

DATA COMMUNICATION  OBJECTIVES To understand and basic To understand and components required for data communication. To analyze the function and To Acquire knowledge of various develop...

DATA COMMUNICATION  OBJECTIVES To understand and basic To understand and components required for data communication. To analyze the function and To Acquire knowledge of various developed for internet. UNIT I NETWORK FUNDAMENTALS Introduction to Networks – Categories of Networks -Communication model –Data transmission concepts and terminology – Protocol architecture – Protocols – OSI – TCP/IP – LAN Topology - Transmission media.  UNIT II DATA LINK LAYER Data link control – Error Detection – VRC – LRC – CRC – Checksum – Error Correction – Hamming Codes – MAC – Ethernet, Token ring , Token Bus – Wireless LAN - Bluetooth – Bridges.  UNIT III NETWORK LAYER Network layer – Switching concepts – Circuit switching – Packet switching – IP Addressing –IPV4, IPV6 – Routing Protocols – Distance Vector – Link State.  UNIT IV TRANSPORT LAYER Transport layer – service – Connection establishment – Flow control – Transmission control protocol – Congestion control and avoidance – User datagram protocol - Transport for Real Time Applications (RTP).  UNIT V APPLICATIONS Applications - DNS – E-Mail Protocols – WWW – SNMP – SMTP - Security – Threats and Services- Cryptography -DES- RSA- Web security -SSL.  OUTCOMES Able to trace the flow of information from one node to another node in the network. Able to Identify the components required to build different types of networks. Able to understand the functionalities needed for data communication into layers. Able to choose the required functionality at each layer for given application. Able to understand the working principles of various application protocols. Acquire knowledge about security issues and services available.  REFERENCES 1. Forouzan, “ Data Communication and Networking”, Fifth Edition , TMH 2012 2. Larry L. Peterson & Bruce S. Davie, “Computer Networks – A systems Approach”, Fourth Edition, Harcourt Asia / Morgan Kaufmann, 2010. 3.William Stallings, “Data and Computer Communications”, Nineth Edition, Prentice Hall 2011. 4. Andrew S.Tannenbaum David J. Wetherall, “Computer Networks”Fifth Edition , Pearson Education 2011 5. James F. Kurose, Keith W. Ross, “Computer Networking: A Top-down Approach, Pearson Education, Limited, sixth edition,2012. 6. John Cowley, “Communications and Networking : An Introduction”, Springer Indian Reprint, 2010.  UNIT – I NETWORK FUNDAMENTALS  OVERVIEW Introduction to Networks Categories of Networks Communication Model Data Transmission Concepts and Terminology Protocol Architecture Protocols OSI TCP/IP LAN Topology Transmission Media  Introduction to Networks A Network: A group of devices that can communicate with each other over links. Each device is called a host. Each host has a unique address.  Network is a connection between two or more devices. Which is connected by a communication links. A node can be computer, printer or any other devices which is capable of sending and receiving information at each other. Example:  INTERNET An internet: each host has an address of the form n/h where n is the network number and h is the number of the host on network n.  Uses of Network It is Used for i) Business Application ii) Home Application iii) Mobile Users iv) E-Mail  Categories or Types of Network There are Three Types: 1. LAN - Local Area Network 2. MAN - Metropolitan Area Network 3. WAN – Wide Area Network 1. LAN - Local Area Network A LAN is Designed by Local Area Connections such as: i) within Building ii) within office iii) within Campus iv) within Specific Place Advantages : 1) Sharing of Files. 2) Sharing of Programs. 3) Communication Exchange. Disadvantages : 1) Reliability. 2) Capacity. 3) High Cost. 2. MAN - Metropolitan Area Network A Metropolitan Area Network (MAN) is a network that interconnects users with computer resources in a geographic area or region larger than that covered by even a large local area network (LAN) but smaller than the area covered by a wide area network (WAN).  MAN supports up to 150 Kilometers Distance. Example: → Telephone Network → Cable TV Advantages : 1) High Bandwidth. 2) It support Large number of Clients. 3) Reduce the Errors. Disadvantages : 1) Large Space Requirements. 2) Slower Data Access. 3) High Cost. 3. WAN – Wide Area Network WAN Provide a Long Distance Transmission of Data. By Using WAN Exchange the Information from one country to another country.  Components of Network - Which gives the Request. - Which gives the Response. - It Indicates Modulator / Demodulator. - Which identifies the Path between Client & Server. - Which overcomes the Traffic problems.  Communication Model Data communications are exchange of data between two devices via some transmission medium. It should be done in two ways i) Local - It takes LAN Connection. ii) Remote - It takes Long distance like MAN & WAN. Data should be Transferred in the form of 0’s and 1’s  Transmission Source Medium Destination 1) Delivery - The System must deliver the data to the correct Destination. 2) Accuracy - The System must deliver the data at Accurate way. 3) Timeline - The System must deliver the data at Exact Time. 4) Jitter - It refers to the variable in the i) Sender iv) Message ii) Receiver v) Protocol iii) Medium 5. Protocol 5. Protocol Step : 1 4. Message Step : 1 Step : 2 Step : 2 1. Sender 3. Medium 2. Receiver  : It is a device , that Sends the information to the Receiver. : It is a device , that Receives the information from the Sender. : It is the physical path between Sender to Receiver. : This is the passing Informations. : It is a set of rules and regulations that “ Governed “ from data communication.  Data Transmission occurs between sender and receiver over some Transmission Medium or Transmission Media. Transmission Media may be classified into Two Types : i) Guided Media [Wired Technology] ii) Unguided Media [Wireless Technology] i) Guided Media (Wired Network) In Guided Media Signals are Passed in a “ same physical path” Example: i) Twisted pair Cable ii) Coaxial Cable iii) Fiber Optic Cable ii) Unguided Media (Wireless Network) In Unguided Media Signals are Passed in the form of “ Electromagnetic Waves” Example : i) Mobile phones ii) Satellite microwave iii) Infrared  It Provides a dedicated links between two devices. For example, a wired system that connects two computers together can be thought of a point- to-point link.  It is a link between two or more devices. It is also known as Multi- Point configuration. The networks having multipoint configuration are called  Transmission Mode ◼ It refers to the direction of information flow between two devices. ◼ Data flow is the flow of data between 2 points. ◼ The direction of the data flow can be described as ◼ Simplex Mode ◼ Half-Duplex Mode ◼ Full-Duplex Mode ◼ Simplex: Data flows in only one direction on the data communication line (medium). Examples are Radio and Television broadcasts. ◼ Half-Duplex: Data flows in both directions but only one direction at a time on the data communication line. Ex. Conversation on walkie-talkies. ◼ Full-Duplex: Data flows in both directions simultaneously. Modems are configured to flow data in both directions. Ex. Phone Conversation  Data Flow Figure 1.2 Data flow (simplex, half-duplex, and full-duplex)  Protocol Architecture It is a layered structure of H/W and S/W that supports exchange of data b/w systems It supports distributed applications(E-Mail, File Transfer) Each layer of protocol architecture provides some set of rules There are 2 widely used protocol architecture ✓TCP/IP Architecture ✓OSI Model  Protocol Protocol is a set of rules that govern data communication It represents what is communicated, when it is communicated and how it is communicated. There are 3 key elements ✓Syntax ✓Semantics ✓Timing  Syntax It represents structure, Format of data the order in which it is presented Data may contain: First 8 bit -> Sender Address Second 8 bit -> Receiver Address Remaining bits-> message stream  SEMANTICS It refers the meaning of each section of bit TIMING It refers when data sent and how fast it is sent (Says Characteristics) Ex:100Mbps  It provides model for the development of product regardless of individual manufacturer It falls in 2 categories  De Facto standard Not officially adopted but used widespread It has 2 categories Proprietary->Wholly owned by company Non-Proprietary->Group or communiy developed for public  De Jure Standard A Standard Legislated by an officially recognized body Standard Organizations: International Standard Organization ANSI IEEE  The OSI Model An ISO (International standard Organization) that covers all aspects of network communications is the Open System Interconnection (OSI) model. An open system is a model that allows any two different systems to communicate regardless of their underlying architecture (hardware or software). The OSI model is not a protocol; it is model for understanding and designing a network architecture that is flexible, robust and interoperable.  The OSI model is a layered framework for the design of network systems that allows for communication across all types of computer systems. The OSI model is built of seven ordered layers: 1. (Layer 1) Physical layer 2. (Layer 2) Data link layer 3. (Layer 3) Network layer 4. (Layer 4) Transport layer 5. (Layer 5) Session layer 6. (Layer 6) Presentation layer 7. (Layer 7) Application layer  Peer-to-Peer Process Within a single machine, each layer calls upon services of the layer just below it. Layer 3, for example, uses the services provided by layer 2 and provides services for layer 4. Between machines, layer x on one machine communicates with layer x on another machine, by using a protocol (this is Peer-to-Peer Process). Communication between machines is therefore a peer-to- peer process using protocols appropriate to a given layer.  Interfaces between Layers There is an interface between each pair of adjacent layers. This interface defines what information and services a layer must provide for the layer above it.  Functions of Layers 1. Physical Layer The physical layer is responsible for transmitting individual bits from one node to the next.  Physical layer The physical layer is concerned with the following: Physical characteristics of interfaces and media: It define the type of transmission media Representation of the bits: the physical layer data consist of a stream of bits(0,1). The transmitted bits must be encoded into signals – electrical or optical. The physical layer defines the type of encoding. Data rate: The physical layer defines the transmission rate, the number of bits sent each second.  Physical Layer Line configuration: the physical layer is concerned with the connection of devices to the medium. Physical topology – Ring, star Transmission Mode - Simplex, Half duplex Full Duplex  2. Data Link Layer It is responsible for node-to-node delivery of data. Functions of the Data Link Layer: Framing. The data link layer divides the stream of bits received from the network layer into data units called frames. Physical addressing. If frames are to be distributed to different systems on the network, the data link layer adds a header to the frame to define the physical address of the sender (source address) and/or receiver (destination address) of the frame. If the frame is intended for a system outside the sender’s network, the receiver address is the address of the device that connects one network to the next.  Flow Control. If the rate at which the data are absorbed by the receiver is less than the rate produced in the sender, the data link layer imposes a flow control mechanism to prevent overwhelming the receiver. Error control. The data link layer adds reliability to the physical layer by adding mechanisms to detect and retransmit damaged or lost frames. Error control is normally achieved through a trailer to the end of the frame. Access Control. When two or more devices are connected to the same link, data link layer protocols are necessary to determine which device has control over the link at any time.  3. Network Layer The Network layer is responsible for the source-to- destination delivery of a packet possible across multiple networks. It converts Frames into packets. If two systems are connected to the same link, there is usually no need for a network layer. However, if the two systems are attached to different networks, there is often a need for the network layer to accomplish source-to-destination delivery.  Network Layer Functions: Logical addressing-Physical addressing (May change) handle addressing problem locally If packet pass the network boundary, we need another addressing called logical addressing (Never change) Routing - Route the packet to final destination The network layer is responsible for the delivery of packets from the original source to the final destination.  4. Transport Layer The transport layer is responsible for process-to-process or end-end delivery of the entire message. The network layer oversees host-to-destination delivery of individual packets, it does not recognize any relationship between those packets. The transport layer ensures that the whole message arrives intact and in order, overseeing both error control and flow control at the process-to-process level.  Transport layer The transport layer is responsible for delivery of a message from one process to another.  Functions of the Transport layer Service point addressing: Computer often run several processes (running programs) at the same time. Process-to-process delivery means delivery from a specific process on one computer to a specific process on the other. The transport layer header include a type of address called port address. The network layer gets each packet to the correct computer; the transport layer gets the entire message to the correct process on that computer.  Cont.. , Segmentation and reassembly: a message is divided into transmittable segments, each having a sequence number. These numbers enable the transport layer to reassemble the message correctly upon arrival at the destination. Connection control: The transport layer can be either connectionless or connection-oriented. A connectionless transport layer treats each segment as an independent packet and delivers it to the transport layer at the destination machine. A connection-oriented transport layer makes a connection with the transport layer at the destination machine first before delivering the packets. After all the data are transferred, the connection is terminated.  Functions of the transport layer Flow control: the transport layer performs a flow control end to end. The data link layer performs flow control across a single link. Error control: the transport layer performs error control end to end. The data link layer performs control across a single link. Congestion control concerns controlling traffic entry into a telecommunication networks so as to avoid congestive collapse by attempting to avoid oversubscription of any of the processing or link capabilities of the intermediate nodes and networks and taking resource reducing steps, such as reducing the rate of sending packets. It should not be confused with flow control, which prevents the sender from overwhelming the receiver.  5. Session Layer The session layer is responsible for dialog control and synchronization.  Functions of Session Layer Decision Control:- Half duplex, Full Duplex Synchronization: Adding checkpoints to stream data. Ex: System sending 2000 pages. Add check point after each 100th page. So in case of failure no need to sent whole page.  6. Presentation Layer It is concerned with the syntax and semantics of the information exchanged b/w 2 devices.  Functions of Presentation Layer Translation: Interoperability b/w different encoding formats. Encryption: Converting plain to cipher text and vice versa. Compression: Reducing number of bits in multimedia data when transmitting.  7. Application layer The application layer is responsible for providing services to the user.  Functions of Application Layer It provides user access to network. X.500-Directory service(is a global directory service. Its components cooperate to manage information about objects such as countries, organizations, people, machines, and so on in a worldwide scope). X.400-Message handling service (is an alternative to the more common SMTP email protocol). FTAM- File Transfer Access and management. Network Virtual Terminal.  Transmission Control Protocol / Internetworking Protocol is used in the internet and is developed prior to the OSI model. It would not match exactly with OSI model It is divided into layers. TCP/IP protocol  It contains relatively independent protocols that can mixed and matched with depend on needs of the system.  It defines the Physical (or) Logical arrangement of Links in a Network. Topology refers to the layout of connected devices in a network. The Topology of the Network is Geometric Representation of the relationship between all Communication links.  Types of Topology i) Mesh Topology ii) Star Topology iii) Tree Topology iv) Bus Topology v) Ring Topology vi) Hybrid Topology  Types of Topology Here every device has a direct point to point link between every other device. A fully connected mesh can have n(n-1)/2 physical channels to link n devices. if n=5 (Number of Nodes) 5(5-1)/2 = 10 ( Communication Links) 5 Nodes are Connected by using 10 Communication Links Mesh Topology  Mesh Topology Advantages: It eliminate the traffic problem. It is robustness. It has privacy and security. Fault can be easily found.  Mesh Topology Disadvantages: More number of cables to be used. Every devices must be connected to some other devices. So installation process is very difficult.  Types of Topology Each device has a dedicated point-to-point link between only a central controller or “HUB”. The devices are not directly linked to some other devices. If one device wants to send data to another device, it sends to the central controller and the Central controller send to other device.  Star Topology Star Topology Diagram: A B Central controller (or) HUB C D  Star Topology Advantages : Less expensive than Mess topology. Less number of cables to be used. It is robustness.  Star Topology Disadvantages: Each device must connected to central controller. It require more installation process. If central controller failure means all the devices should be failed.  Types of Topology Tree topology has some variation from star topology. The nodes in the tree are linked to the central controller. The primary HUB in the tree is represented by “Active Hub”. The secondary HUB in the tree is represented by “Passive Hub”. Tree Topology  Tree Topology Advantages: It allows more devices to be attached in a single central controller. It allows the network to prioritize the communication.  Tree Topology Disadvantages: Each device must be linked to central controller. It require more installation processes. If central controller failure means entire system should fail down.  Types of Topology A Bus topology describes the multipoint configuration. One long cable act as a backbone to link all the devices in a network. Devices are connected in a bus topology with the help of “Drop lines” and “Tapes”.  Bus Topology Bus Topology Diagram: A B C D Back bone Drop line Drop line Tape Back bone  Bus Topology Advantages: Installation process is very easy. Redundancy can be eliminated. Less number of cables to be used.  Bus Topology Disadvantages: Reconfiguration is very difficult. Very difficult to adding (or) deleting of a devices  Types of Topology In Ring Topology each device has dedicated point-to-point link between other devices. The signals are passed along the “ring” in only one direction from device to device. Each devices in a ring should have a “Repeater”.  Ring Topology Ring Topology Diagram: A B D Ring C  Ring Topology Advantages: Easy to install and reconfigure. Fault can be easily identified.  Ring Topology Disadvantages: It is unidirectional traffic. In rings if one device gets failure then the entire system should be failed. VI. Hybrid Topology ◼ Combination of all topology is called hybrid topology.