Transcript TOPIC 1.2
TOPIC 1.2 INTRODUCTION TO NETWORKING OBJECTIVES By the end of the topic, students should be able to: a) List the elements of data communication systems. b) Describe the communication devices: Wired Wireless c) Describe basic data transmission concepts d) Define common transmission flaws affecting data signals. e) Define rules of communications f) Explain the signal transmission DATA COMMUNICATION SYSTEM ELEMENTS Data Elements Communication Devices Electronic Communication Methods Transmission Media DATA ELEMENTS Message Sender Receiver Medium Protocol COMMUNICATION DEVICES A hardware component that enables a computer to send and receive data, instructions and information and from one or more computers. Type of communication devices: Wired (Data Terminal Equipment (DTE)) Wireless (3G,GPRS, laptop, mobile phones) COMMUNICATION DEVICES Wired Serial Wires are used for high end connectivity between different devices and widely used on layer 3. DTE ( data terminal equipment) and DCE (data circuit-terminating equipment / data communications equipment). Ethernet Cables (UTP) COMMUNICATION DEVICES Wireless Devices COMMUNICATION DEVICES REPEATER ~ increasing the signals energy HUB / SWITCH Centralizing connection for all network devices Sending packets using MAC address BRIDGE ~ Connecting two or more different networks for communication ROUTER ~ Forwarding packets in the network using MAC and IP address GATEWAYS ~ a device that acts as a “MAIN PATH” for all network traffics Electronic communication methods Email Instant Messaging Transmission media Guided Media Twisted-Pair Cable Coaxial Cable Fiber Optic Cable Unguided Media: Wireless Transport electromagnetic waves without using a physical conductor Transmission media Twisted-Pair Cable • • Color-coded pairs of insulated copper wires twisted around each other and encased in plastic coating Twists in wire help reduce effects of crosstalk • • Number of twists per meter or foot known as twist ratio Alien Crosstalk • When signals from adjacent cables interfere with another cable’s transmission Shielded Twisted-Pair (STP) STP cable consists of twisted wire pairs that are individually insulated and surrounded by shielding made of metallic substance Unshielded Twisted-Pair Consists of one or more insulated wire pairs encased in a plastic sheath Does not contain additional shielding To manage network cabling, it is necessary to be familiar with standards used on modern networks, particularly Category 3 (CAT3) and Category 5 (CAT5) Comparing STP and UTP Throughput Cost Both use RJ-45 connectors (see Figure 4-27) and data jacks Noise immunity Typically, STP is more expensive Connector Both can transmit up to 100 Mbps STP is more noise-resistant Size and scalability Maximum segment length for both is 100 meters Fiber-Optic Cable Contains one or several glass fibers at its core Surrounding the fibers is a layer of glass called cladding Single-mode Carries light pulses along single path Multimode fiber fiber Many pulses of light generated by LED travel at different angles Unguided Media: Wireless Infrared transmission Infrared networks use infrared light signals to transmit data through space Direct infrared transmission depends on transmitter and receiver remaining within line of sight In indirect infrared transmission, signals can bounce off of walls, ceilings, and any other objects in their path RF transmission Radio frequency (RF) transmission relies on signals broadcast over specific frequencies Two most common RF technologies: Narrowband Spread spectrum DATA TRANSMISSION CONCEPTS Analog and digital signaling Data modulation Simple, half-duplex and full-duplex Multiplexing Point-to-point transmission Broadcast transmission Bluetooth, 3G Throughput Bandwidth TRANSMISSION FLAWS Noise Occurred when devices act as a sending antenna and the transmission medium act as the receiving antenna. Attenuation Loss of signal strength as transmission travels away from source Analog signals pass through an amplifier, which increases not only voltage of a signal but also noise accumulated An analog signal distorted by noise, and then amplified TRANSMISSION FLAWS Latency Electromagnetic interference (EMI) Latency is the delay between requesting data and the receipt of a response, or in the case of one-way communication, between the actual moment of a signal's broadcast and the time it is received at its destination Interference that may be caused by motors, power lines, television, copiers, fluorescent lights, or other sources of electrical activity Radiofrequency interference (RFI) Interference that may be generated by motors, power lines, televisions, copiers, fluorescent lights, or broadcast signals from radio or TV towers TRANSMISSION FLAWS Distortion Signal changes its form or shape. Made of different frequencies. Regeneration Process of retransmitting a digital signal Repeater Device used to regenerate a signal A digital signal distorted by noise, and then repeated