COE 342 1 Data and Computer Communications Data

COE 342 - 1 Data and Computer Communications Data Communications & Networking Overview

Communication Model COE 205 Term 042 Dr. Talal Al. Kharobi 2

Communication Model Ø Fundamental purpose of communications system is exchange of data between two parties Ø The key elements of a communication model are Ø Source: Generates data to be transmitted Ø Transmitter: Converts data into transmittable signals (modulation, encoding, …) Ø Transmission System: Carries data Ø Receiver: Converts received signal into data (the opposite of the “Transmitter” role) Ø Destination: Takes incoming data COE 205 Term 042 Dr. Talal Al. Kharobi 3

Communications Tasks Ø Transmission system utilization Ø Interfacing Ø Signal generation Ø Synchronization Ø Exchange management Ø Error detection and correction Ø Flow control Ø Addressing Ø Routing Ø Recovery Ø Message formatting Ø Security Ø Network management COE 205 Term 042 Dr. Talal Al. Kharobi 4

Communications Tasks Ø Transmission system utilization Ø Making efficient use of transmission facilities Ø Multiplexing is used to allocate the total transmission medium among number of users Ø Congestion control is needed to assure that the transmission system is not overwhelmed Ø Interfacing: Interfacing here refers to how to interface communicating devices to the transmission system Ø Signal generation : Most forms of computer communication depend on the use of electromagnetic signals propagated over transmission media. Thus, we need to generate signals from the data to be transmitted. COE 205 Term 042 Dr. Talal Al. Kharobi 5

Communications Tasks Ø Synchronization: The receiver needs to know when the signal start and ends. Also, it needs to know the duration of each signal Ø Exchange management: The communicating parties need to agree on a variety of requirements to communicate usefully. Such conventions include Ø Signal timing Ø How to start/end conversation Ø Simultaneous transmission or taking turns Ø Amount of data to be sent at one time Ø Data format Ø Dealing with errors COE 205 Term 042 Dr. Talal Al. Kharobi 6

Communications Tasks Error detection and correction: Ø In all communication system there is a potential for error (signal d istortion, attenuation, interference) Ø In most cases, error in transmission is not accepted (tolerated) Ø We need to have a technique to detect errors in transmission and even better to have a technique to correct errors Ø Flow control: Flow control is required to assure that the source does not send information too fast Ø Addressing: When more than two devices share transmission facility: Ø Each system need to have unique address. Ø Source need to identify the destination by its address. COE 205 Term 042 Dr. Talal Al. Kharobi 7

Communications Tasks Ø Routing: the transmission system must assure that the destination system receive the data Ø Recovery: Recovery is needed when the information exchange is interrupted or to restore the system to the point prior to the beginning of the exchange Ø Message formatting: Communicating parties need to agree on the form of data to be transmitted such as the binary code for characters Ø Security: Ø Data sender need to assure that only the intended destination receive the data. Ø Destination need to be sure that what he recived was sent actually by the purported sender. Ø Destination need to be sure that the data has not been altered COE 205 Term 042 Dr. Talal Al. Kharobi 8

Communications Tasks Ø Network management: Network management is needed to Ø configure the system Ø Monitor the system status Ø React to failures and overload Ø Plan for future growth COE 205 Term 042 Dr. Talal Al. Kharobi 9

Data Communication Sending an email (simplified) Ø User A wrote an email message and he wants to send it to B Ø When the user click send, the email program will prepare binary message that has the digital equivalent of email body, B address and some control bit streams. Ø The computer will send the bit stream as a digital signal to the transmitter (modem for example) Ø Transmitter will convert the digital signal to a signal suitable for the transmission system (analog signal for example) Ø Transmission system will carry the signal to the destination recover. Ø The receiver convert the received signal to a binary signal and send it to the computer Ø Destination computer will take the received signal convert it to binary data and store it in the memory Ø Email program will read the binary data removes added COE 205 Term 042 Dr. Talal Al. Kharobi 10

Simplified Data Communication Model COE 205 Term 042 Dr. Talal Al. Kharobi 11

Direct point to point connection COE 205 Term 042 Dr. Talal Al. Kharobi 12

Direct point to point connection COE 205 Term 042 Dr. Talal Al. Kharobi 13

Computer network Ø Computer network is a group of computer systems linked together. Ø Computer networks can be classified in different ways. Follows is a classification that depends on the geographical position of the computers: Ø WAN: wide-area network: The computers are farther apart and are connected by telephone lines or radio waves. Ø MAN: metropolitan-area network: A data network designed for a town or city. Ø CAN: campus-area network: The computers are within a limited geographic area, such as a campus or military base. Ø LAN: local-area network: The computers are geographically close together (in the same building). Ø HAN: home-area network: A network contained within a user's home that connects a person's digital devices. COE 205 Term 042 Dr. Talal Al. Kharobi 14

Local-area network Ø A computer network that spans a relatively small area. Ø Most LANs are confined to a single building or group of buildings. Ø A LAN can be connected to other LANs over any distance via telephone lines or radio waves. A system of LANs connected in this way is called a wide-area network (WAN). Ø Most LANs connect workstations and personal computers. Ø Each node (individual computer ) in a LAN has its own CPU with which it executes programs, but it also is able to access data and devices anywhere on the LAN. Ø Users can share devices, such as printers, as well as data. Ø Users can also use the LAN to communicate with each other, by sending e-mail or engaging in chat sessions. Ø There are many different types of LANs examples Ø Ethernets being the most common for PCs. Ø Apple. Talk is most common for Apple Macintosh networks COE 205 Term 042 Dr. Talal Al. Kharobi 15

Ethernet Ø A local-area network (LAN) architecture developed by Xerox Corporation in cooperation with DEC and Intel in 1976. Ø Ethernet uses a bus or star topology Ø Ethernet data transfer rates: Ø Ethernet: 10 Mbps. Ø Fast Ethernet: 100 Mbps. Ø Gigabit Ethernet: 1 gigabit (1, 000 megabits) per second Ø The Ethernet specification served as the basis for the IEEE 802. 3 standard Ø It is one of the most widely implemented LAN standards. COE 205 Term 042 Dr. Talal Al. Kharobi 16

Wide Area Network Ø A computer network that spans a relatively large geographical area. Ø Typically, a WAN consists of two or more local-area networks (LANs). Ø Computers connected to a wide-area network are often connected through public networks, such as the telephone system. Ø They can also be connected through leased lines or satellites. Ø The largest WAN in existence is the Internet. COE 205 Term 042 Dr. Talal Al. Kharobi 17

Metropolitan Area Network Ø A data network designed for a town or city. Ø In terms of geographic breadth, MANs are larger than local-area networks (LANs), but smaller than wide-area networks (WANs). Ø MANs are usually characterized by very high-speed connections using fiber optical cable or other digital media. COE 205 Term 042 Dr. Talal Al. Kharobi 18

Wireless network Ø Wireless network is a type of network that uses high-frequency radio waves rather than wires to communicate between nodes. Ø Hybrid wireless network is an emerging networking that consists of wireless components that communicate with a network that uses cables in a mixed-component network. Ø Wireless network is now common in Ø Business LANs Ø WAN (voice & data) Ø Advantages of using wireless network: Ø Easy to install and configure. Ø Provides mobility COE 205 Term 042 Dr. Talal Al. Kharobi 19

Network technology Ø Ø Circuit switching Packet switching Frame relay Asynchronous Transfer Mode (ATM) COE 205 Term 042 Dr. Talal Al. Kharobi 20

Circuit switching Ø A type of communications in which a dedicated channel (or circuit) is established for the duration of a transmission. Ø The most famous circuit-switching network is the telephone system, which links together wire segments to create a single unbroken line for each telephone call. Ø Circuit-switching systems are ideal for communications that require data to be transmitted in real-time such as live audio and video. Ø Circuit-switching networks are sometimes called connectionoriented networks. COE 205 Term 042 Dr. Talal Al. Kharobi 21

Packet switching Ø Communication method that divides messages into packets and sends each packet individually. Ø Each packet is then transmitted individually and can even follow different routes to its destination. Ø Once all the packets forming a message arrive at the destination, they are recompiled into the original message. Ø Packet-switching networks are more efficient if some amount of delay is acceptable. as e-mail messages and Web pages. Ø The Internet is based on a packet-switching protocol, TCP/IP. Ø Most modern Wide Area Network (WAN) protocols, including TCP/IP, X. 25, and Frame Relay, are based on packet-switching technologies. COE 205 Term 042 Dr. Talal Al. Kharobi 22

Frame relay Ø Packet switching systems have large overheads to compensate for errors. Ø Modern systems are more reliable (dramatically lower errors rate) Ø Errors can be caught in end system Ø Most overhead for error control is stripped out Ø Frame relay is a packet-switching protocol that uses much lesser overhead for error control. Ø Frame Relay networks can support data transfer rates up to 2 Mbps (compared to 64 Kbps for regular packet switching) Ø Frame Relay is quite popular in the U. S. because it is relatively inexpensive. However, it is being replaced by faster technologies, such as ATM. COE 205 Term 042 Dr. Talal Al. Kharobi 23

Asynchronous Transfer Mode (ATM) Ø A network technology based on transferring data in cells or packets of a fixed size. Ø The cell used with ATM is relatively small compared to units used with older technologies. Ø The small, constant cell size allows ATM equipment to transmit video, audio, and computer data over the same network, and assure that no single type of data hogs the line. Ø ATM creates a fixed channel, or route, between two points whenever data transfer begins. Ø ATM attempts to combine the best of both worlds -- the guaranteed delivery of circuit-switched networks and the robustness and efficiency of packet-switching networks. Ø Speed up to Gbps range COE 205 Term 042 Dr. Talal Al. Kharobi 24

Transmission Control Protocol/Internet Protocol (TCP/IP) Ø A suite of communications protocols used to connect hosts on the Internet. Ø TCP/IP uses several protocols, the two main ones being TCP and IP. Ø TCP/IP establishes a connection between two hosts so that they can send messages back and forth for a period of time. Ø TCP is a protocols that enables two hosts to establish a connection and exchange streams of data. Ø TCP establishes a virtual connection between a destination and a source. Ø TCP guarantees delivery of data and also guarantees that packets will be delivered in the same order in which they were sent. Ø IP specifies the format of packets, also called datagrams, and the addressing scheme. Ø IP is like the postal system: It allows you to address a package and drop it in the system, but there's no direct link between you and the recipient. COE 205 Term 042 Dr. Talal Al. Kharobi 25

Networking Configuration Subscriber connection Ø Telephone network Ø DSL Ø Cable TV Ø Satellite SONet: Synchronous Optical Network, a standard for connecting fiber-optic transmission systems. COE 205 Term 042 Dr. Talal Al. Kharobi 26