SAE6A/SAZ6B DATA COMMUNICATION AND NETWORKING UNIT : I To V 1
UNIT 1:Syllabus Introduction to Data Communication Network Protocols & standards standards organizations Line Configuration Topology Transmission mode Classification of Network OSI Model Layers of OSI Model. 2
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. Components of a data communication system SAE6A \SAZ6B Data Communication and Networks 3 Slide number / Total slides
Data flow (simplex, halfduplex, 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. 4
Network topology mesh topology SAE6A\ SAZ6B Data Communication and Networks Star topology 5
Bus topology Ring topology Hybrid topology SAE6A \SAZ6B Data Communication and Networks 6
Categories of Networks Local Area Networks (LANs) Short distances Designed to provide local interconnectivity Wide Area Networks (WANs) Long distances Provide connectivity over large areas Metropolitan Area Networks (MANs) Provide connectivity over areas such as a city, a campus SAE6A\ SAZ6B Data Communication and Networks 7
LAN WAN 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 and timing 8
Standards organisation IEEE (Institute of Electrical and Electronics Engineers) ANSI(American National Standards Institute) ITU (International Telecommunications Union - formerly CCITT) ISO (International Organization for Standards) EIA (Electronic Industries Association) ETSI (European Telecommunications Standards Institute) W3C - World Wide Web Consortium 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. SAE6A \SAZ6B Data Communication and Networks 9
The interaction between layers in the OSI model 10
Physical layer The physical layer is responsible for movements of individual bits from one hop (node) to the next. Data link layer The data link layer is responsible for moving frames from one hop (node) to the next. SAE6A\ SAZ6B Data Communication and Networks 11
Source-to-destination delivery Transport layer SAE6A \SAZ6B Data Communication and Networks 12
Process -to-process delivery of a message Session layer Presentation layer Application layer 13
UNIT 2:Syllabus Parallel and Serial Transmission DTE/DCE/ EIA-449 EIA-530 EIA-202 x.21 interface Interface standards Modems Guided Media Unguided Media Performance Types of Error Error Detection Error Corrections 14
TRANSMISSION MODES The transmission of binary data across a link can be accomplished in either parallel or serial mode. In parallel mode, multiple bits are sent with each clock tick. In serial mode, 1 bit is sent with each clock tick. While there is only one way to send parallel data, there are three subclasses of serial transmission: asynchronous, synchronous, and isochronous. Data transmission and modes SAE6A \SAZ6B Data Communication and Networks 15
Parallel transmission Serial transmission In asynchronous transmission, we send 1 start bit (0) at the beginning and 1 or more stop bits (1s) at the end of each byte. There may be a gap between each byte. Asynchronous transmission SAE6A \SAZ6B Data Communication and Networks 16
In synchronous transmission, we send bits one after another without start or stop bits or gaps. It is the responsibility of the receiver to group the bits. The bits are usually sent as bytes and many bytes are grouped in a frame. A frame is identified with a start and an end byte. Synchronous transmission Isochronous In isochronous transmission we cannot have uneven gaps between frames. Transmission of bits is fixed with equal gaps. SAE6A \SAZ6B Data Communication and Networks 17
DTE-DCE Interface DTE(Data Terminal equipment) DCE(Data Circuit-terminating Equipment) DTE(Data Terminal Equipment) is any device that is a source of destination for binary digital data terminal Personal computer printer fax machine and so on SAE6A \SAZ6B Data Communication and Networks 18
DTE-DCE Interface(cont d) DCE (Data Circuit-Terminating Equipment) is any device (functional unit) that transmits or receives data in the form of an analog or digital signal through a network Modulator/demodulator SAE6A \SAZ6B Data Communication and Networks 19
Standards EIA (Electronic Industries Association) EIA-232 EIA-442 EIA-449 EIA-232(RS-232) defining the mechanical, electrical and functional characteristics(mechanical specification) defining the interface as a 25-wire cable with a male (plug) and a female (receptacle) DB-25 pin connector length may not exceed 15m(50 feet) (electrical specification) define voltage levels and the type of signal( NRZ-L) SAE6A \SAZ6B Data Communication and Networks 20
Other Interface Standards X.21 is an interface designed by the ITU-T to address many of the problems existing in the EIA eliminating most of the control circuits of the EIA standards DB-15 connector Byte timing (pins 7 and 14) : byte synchronization Control and indication Pin 3 : equivalent of request to send (control) Pin 5 : equivalent of clear to send (indication) 21
Transmission medium Classes of transmission media SAE6A \SAZ6B Data Communication and Networks 22
GUIDED MEDIA Guided media, which are those that provide a conduit from one device to another, include twisted-pair cable, coaxial cable, and fiber-optic cable. Twisted-pair cable UTP connector SAE6A \SAZ6B Data Communication and Networks UTP and STP cables Coaxial cable 23
Optical fiber Modes SAE6A \SAZ6B Data Communication and Networks Propagation modes Fiber construction 24
UNGUIDED MEDIA: WIRELESS Unguided media transport electromagnetic waves without using a physical conductor. This type of communication is often referred to as wireless communication. Electromagnetic spectrum for wireless communication Propagation methods Wireless transmission waves Radio waves are used for multicast communications, such as radio and television, and paging systems. SAE6A \SAZ6B Data Communication and Networks 25
Wireless Channels Are subject to a lot more errors than guided media channels. Interference is one cause for errors, can be circumvented with high SNR. The higher the SNR the less capacity is available for transmission due to the broadcast nature of the channel. Channel also subject to fading and no coverage holes. Error Detection and correction There are many reasons such as noise, cross-talk etc., which may help data to get corrupted during transmission. Types of Errors: Single bit error In a frame, there is only one bit, anywhere though, which is corrupt. Multiple bits error Frame is received with more than one bits in corrupted state. Burst error Frame contains more than1 consecutive bits Corrupted. SAE6A \SAZ6B Data Communication and Networks 26
Error control mechanism Error detection Error correction Error Detection Errors in the received frames are detected by means of Parity Check and Cyclic Redundancy Check (CRC). Parity Check One extra bit is sent along with the original bits to make number of 1s either even in case of even parity, or odd in case of odd parity. 27
Cyclic Redundancy Check CRC is a different approach to detect if the received frame contains valid data. This technique involves binary division of the data bits being sent. The divisor is generated using polynomials. The sender performs a division operation on the bits being sent and calculates the remainder. Before sending the actual bits, the sender adds the remainder at the end of the actual bits. Actual data bits plus the remainder is called a codeword. The sender transmits data bits as codewords. At the other end, the receiver performs division operation on codewords using the same CRC divisor. If the remainder contains all zeros the data bits are accepted, otherwise it is considered as there some data corruption occurred in transit. 28
Error Correction In the digital world, error correction can be done in two ways: Backward Error Correction When the receiver detects an error in the data received, it requests back the sender to retransmit the data unit. Forward Error Correction When the receiver detects some error in the data received, it executes error-correcting code, which helps it to auto-recover and to correct some kinds of errors. SAE6A \SAZ6B Data Communication and Networks 29
UNIT 3:Syllabus Multiplexing Types of Multiplexing Multiplexing Application Telephone system Project 802 Ethernet Token Bus Token Ring FDDI IEEE 802.6 SMDS Circuit Switching Packet Switching Message switching Connection Oriented and Connectionless services. SAE6A \SAZ6B Data Communication and Networks 30
MULTIPLEXING Whenever the bandwidth of a medium linking two devices is greater than the bandwidth needs of the devices, the link can be shared. Multiplexing is the set of techniques that allows the (simultaneous) transmission of multiple signals across a single data link. As data and telecommunications use increases, so does traffic. Dividing a link into channels 31
Categories of multiplexing FDM process Frequency-division multiplexing (FDM) FDM is an analog multiplexing technique that combines analog signals. 32
Wavelength-division multiplexing (WDM) WDM is an analog multiplexing technique to combine optical signals. Prisms in wavelength-division multiplexing and demultiplexing Time Division Multiplexing (TDM) TDM is a digital multiplexing technique for combining several low-rate digital channels into one high-rate one. 33
Synchronous time-division multiplexing In synchronous TDM, the data rate of the link is n times faster, and the unit duration is n times shorter. Interleaving The process of taking a group of bits from each input line for multiplexing is called interleaving. We interleave bits (1 - n) from each input onto one output. 34
Digital hierarchy DS and T line rates T-1 line for multiplexing telephone lines E line rates 35
TDM slot comparison 36
IEEE STANDARDS In 1985, the Computer Society of the IEEE started a project, called Project 802, to set standards to enable intercommunication among equipment from a variety of manufacturers. Project 802 is a way of specifying functions of the physical layer and the data link layer of major LAN protocols. IEEE standard for LANs 37
HDLC frame compared with LLC and MAC frames STANDARD ETHERNET The original Ethernet was created in 1976 at Xerox s Palo Alto Research Center (PARC). Since then, it has gone through four generations. We briefly discuss the Standard (or traditional) Ethernet in this section. SAE6A \SAZ6B Data Communication and Networks 38
802.3 MAC frame 10Base5 implementation Unicast and multicast addresses 10Base2 implementation 39
10Base-T implementation 10Base-F implementation Switched Ethernet Fast Ethernet Gigabit Ethernet 40
802.5(token ring) 802.4(token bus) FDDI DQDB 802.6 SMDS The SMDS is designed to connect the multiple LANs together. This is the first high speed broadband service offered to the public. The SMDS network is in the telephone company's office. SMDS is designed to handle bursty service. The type of traffic in interconnected LANs is not continuous but bursty type. i.e. once in a while a packet will be transferred from one LAN td other but otherwise there is no LAN to LAN traffic. So the option of leased lines will be expensive. It will result in high monthly bills. The SMDS is a much cheaper solution to this problem. SMDS are supposed to be fast enough. Standard speed is 45 Mbps. 41
SMDS Switching Switching is process to forward packets coming in from one port to a port leading towards the destination. Connectionless: The data is forwarded on behalf of forwarding tables. No previous handshaking is required and acknowledgements are optional. 42
Connection Oriented Before switching data to be forwarded to destination, there is a need to pre-establish circuit along the path between both endpoints. Data is then forwarded on that circuit. After the transfer is completed, circuits can be kept for future use or can be turned down immediately. Circuit Switching When two nodes communicate with each other over a dedicated communication path, it is called circuit switching Establish a circuit Transfer the data Disconnect the circuit 43
Circuit Switching Message Switching In message switching, the whole message is treated as a data unit and is switching / transferred in its entirety A switch working on message switching, first receives the whole message and buffers it until there are resources available to transfer it to the next hop. If the next hop is not having enough resource to accommodate large size message, the message is stored and switch waits. 44
Message Switching Packet Switching Shortcomings of message switching gave birth to an idea of packet switching. The entire message is broken down into smaller chunks called packets. The switching information is added in the header of each packet and transmitted independently. It is easier for intermediate networking devices to store small size packets and they do not take much resources either on carrier path or in the internal memory of switches. 45
UNIT 4:Syllabus History of Analog and Digital Network Access to ISDN ISDN Layers Broadband ISDN X.25 Layers Packet Layer Protocol A A Topology A Protocol. 46
ISDN Services Voice over Analog Network 47
Voice and Data over Analog Network Analog and Digital Services SAE6A \SAZ6B Data Communication and Networks 48
Integrated Digital Network Integrated Services Digital Network 49
Basic Rate Interface Primary Rate Interface 50
ISDN Layers ISDN Layers for B and D Channels 51
BRI Interfaces S Interface 52
BRI Frame 53
PRI Interfaces PRI Frame 54
LAPD Address Field x.25 layer 55
A Multiplexing with Different Packet Sizes Cell Switching SAE6A \SAZ6B Data Communication and Networks 56
Virtual Path Identifier Switching Using VPI SAE6A \SAZ6B Data Communication and Networks 57
VPI and VCI Switching Using VPI and VCI A Interfaces 58
Public and Private UNIs A Layers AAL Types SAE6A \SAZ6B Data Communication and Networks 59
AAL1 AAL2 60
UNIT 5:Syllabus Repeaters Bridges Routers Gateway Routing algorithms TCP/IP Network Transport and Application Layers of TCP/IP World Wide Web SAE6A \SAZ6B Data Communication and Networks 61
Connecting Devices Connecting Devices and the OSI Model 62
A Repeater A Bridge Function of a Repeater Function of a Bridge 63
Routers in an Internet A Gateway Routing Algorithms The Concept of Distance Vector Routing 64
Distance Vector Routing Table Routing Table Distribution Updating Routing Table for RouterA Final Routing Tables 65
Concept of Link State Routing Cost in Link State Routing Flooding of A s LSP Link State Packet SAE6A \SAZ6B Data Communication and Networks 66
Link State Database Costs in the Dijkstra Algorithm SAE6A \SAZ6B Data Communication and Networks 67
Shortest Path Calculation, Part I Shortest Path Calculation, Part II Shortest Path Calculation, Part III SAE6A \SAZ6B Data Communication and Networks Shortest Path Calculation, Part IV 68
Shortest Path Calculation, Part XIII Routing Table for Router A 69
TCP/IP Protocol Suite Most widely used interoperable network protocol architecture Specified and extensively used before OSIOSI was slow to take place in the market funded by the US Defense Advanced Research Project Agency (DARPA) for its packet switched network (ARPANET) DoD automatically created an enormous market for TCP/IP Used by the Internet and WWW OSI vs. TCP/IP SAE6A \SAZ6B Data Communication and Networks 70
Transport Layer End-to-end data transfer Transmission Control Protocol (TCP) connection oriented reliable delivery of data ordering of delivery User Datagram Protocol (UDP) connectionless service delivery is not guaranteed Can you give example applications that use TCP and UDP? Application Layer Support for user applications A separate module for each different application e.g. HTTP, SMTP, telnet 71
World Wide Web WWW: a portion of the Internet that contains billions of documents World Wide Web Consortium (W3C): an organization issuing standards related to all aspects of the Web Web Site: a location that is accessible from the Internet and makes web pages available Hyperlink or Link: a word that can be clicked to bring another document into view Distribute Hypermedia System: a network-based content development system that uses multimedia resources as a mean of navigation or illustration Dead or Broken Link: a link to documents that have disappeared Web Browser: a program that displays a Web document IE, Netscape Navigator, Mosaic Uniform Resource Locator (URL): a string of characters that precisely identifies an Internet resource s type and location Protocol,Server,Path,Resource Name 72
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