1 SEMESTER Chapter 8 Physical Layer V 4.0 8.1.1 What does the physical layer provide?
90 Points
provides the means to transport across the network media the bits that make up a Data Link layer frame What are the four elements The physical media and associated connectors of delivering frames across A representation of bits on the media the media? Encoding of data and control information Transmitter and receiver circuitry on the network devices 8.1.2 What are the three basic Copper cable forms of media? Fiber Wireless What are the three the Physical layer encodes the bits into the concerns when the physical signals for a particular medium, it must also layer encodes bits? distinguish where one frame ends and the next frame begins 8.1.3 What does the physical hardware, developed by engineers, in the form layer consist of? of electronic circuitry, media, and connectors What are the organizations The International Organization for that are responsible for Standardization (ISO) physical layer standards? The Institute of Electrical and Electronics Engineers (IEEE) The American National Standards Institute (ANSI) The International Telecommunication Union (ITU) The Electronics Industry Alliance/Telecommunications Industry Association (EIA/TIA) National telecommunications authorities such as the Federal Communication Commission (FCC) in the USA. 8.1.3.2 The technologies defined by Physical and electrical properties of the media these organizations include Mechanical properties (materials, dimensions, what four areas of the pinouts) of the connectors Physical layer standards? Bit representation by the signals (encoding) Definition of control information signals 8.1.4 What are the three The physical components fundamental functions of the Data encoding Physical layer? Signaling What are the two values 1 and 0 that the physical layer encodes? 8.2.1 How are the bits of the One bit at a time frame transmitted by the physical layer?
What is a bit time? How are the signaling and receiving ends clocks synchronized in the LAN? What characteristics can be changed to represent bits on the medium? What will happen if there is no agreement between nodes on the signaling method? 8.2.1.2 What are the three characteristics of NRZ signaling? What type of transmission is NRZ suited for? 8.2.1.3 What are represented by in Manchester encoding? How does the transition help maintain clock synchronization? Which medium uses Manchester encoding? 8.2.2 What method is used to signal start and end of a frame in higher speed technologies? 8.2.2.2 What is a code group? What are the advantages of transmitting symbols? What are the four advantages of using code groups?
specific amount of time each signal has to occupy the media Many signaling methods use predictable transitions in the signal to provide synchronization between the clocks of the transmitting and the receiving devices Amplitude Frequency Phase The transmission will fail
Discrete impulses Only two states Voltage jumps between levels for slow speed data links voltage transitions one voltage transition must occur in the middle of each bit time 10BaseT Ethernet Specific pattern of grouped bits
What are the three types of code groups?
consecutive sequence of code bits that are interpreted and mapped as data bit patterns the error detection capabilities and timing synchronization between transmitting and receiving devices are enhanced Reducing bit level error Limiting the effective energy transmitted into the media Helping to distinguish data bits from control bits Better media error detection Data symbols - Symbols that represent the data of the frame as it is passed down to the Physical layer. Control symbols - Special codes injected by the Physical layer used to control transmission. These include end-of-frame and idle media symbols. Invalid symbols - Symbols that have patterns not allowed on the media. The receipt of an invalid symbol indicates a frame error.
8.2.2.3 How does 4B/5B represent a nibble? 8.2.3 What are the three measures for Data Transfer? 8.2.3.2 What is the difference between throughput and goodput? Which measure of data transfer is most important to the end user? 8.3.1 What are the standards for copper media defined for?
as five-bit values known as symbols Bandwidth Throughput Goodput Throughput is the measure of bits over a given time and goodput is the measure of usable data transferred over a given period of time Goodput Type of copper cabling used Bandwidth of the communication Type of connectors used Pinout and color codes of to connections the media Maximum distance of the media RJ-45 Shielding and twisting of the wires
8.3.2
What type of connector is commonly used in copper cabling? 8.3.2.2 What is done to the pairs of wires to minimize signal degradation due to electronic noise? What are the other methods listed to limit the susceptibility of copper cables to noise?
8.3.3
What is crosstalk? What is used to limit crosstalk? What changes in the twist from one pair of wires to the next pair of wires to improve the limitation of crosstalk? What are some of the elements defined by the TIA/EIA 568A standard?
Selecting the cable type or category most suited to protect the data signals in a given networking environment Designing a cable infrastructure to avoid known and potential sources of interference in the building structure Using cabling techniques that include the proper handling and termination of the cables the interference caused by the magnetic field around the adjacent pairs of wires in the cable Twisting pairs of wires The number of twists per meter changes
Why is it wasteful to install less expensive but lower rated cabling? 8.3.3.2 What is UTP cable terminated with?
Cable types Cable lengths Connectors Cable termination Methods of testing cable If the decision is later made to adopt a faster LAN technology, total replacement of the installed cable infrastructure may be required. RJ-45 connectors
What are the three types of Ethernet cables? What is a straight-through used for? What is a crossover used for? What is a rollover used for? What happens if you use the wrong type of cable when connecting devices? What are the other two type of copper cabling? What has replaced the use of coaxial cable in today's Ethernet installations? What type types of materials can be used for fiber optic cabling? What is the encoding method for fiber optic? What are the issues with implementing fiber optic cabling?
Ethernet Straight-through Ethernet Crossover Rollover Host to network device such as a hub or switch Connecting two hosts Connecting to network intermediary devices Connecting a computers serial port to the console port of a router (with an adapter) Communication will not occur 1. Coaxial 2. Shielded Twisted-Pair (STP) UTP Glass or plastic Light pulses More expensive (usually) than copper media over the same distance (but for a higher capacity) Different skills and equipment required to terminate and splice the cable infrastructure More careful handling than copper media Backbone and between buildings optical fiber does not conduct electricity and has low signal loss 2, they can only operate in one direction Single mode and multimode radio and microwave frequencies that represent the binary digits of data communications Security IEEE 802.11 IEEE 802.15 IEEE 802.16 Global System for Mobile Communications (GSM)
8.3.4
8.3.6
What areas usually implement fiber optic cabling? What are the major advantages of using fiber optic between buildings? 8.3.6.2 How many cables are needed for each fiber optic connection? Why? 8.3.6.3 What are the two types of fiber optic cables? 8.3.7 How do wireless media carry electromagnetic signals? What is the major concern for wireless signals? 8.3.7.2 What are the 4 standards for wireless networks?
8.3.7.3 What are the two network devices necessary to implement a wireless network?
8.3.8
What are the WLAN Ethernet standards? What are some of the CAT5 termination that may performed onsite?
8.3.8.2 What are the differences in the termination of the two cables pictured? What could happen if wires are not terminated correctly? 8.3.8.3 What are the three main splicing errors when using fiber optic cabling?
Wireless Access Point (AP) - Concentrates the wireless signals from users and connects, usually through a copper cable, to the existing copper-based network infrastructure such as Ethernet. Wireless NIC adapters - Provides wireless communication capability to each network host. IEEE 802.11a, IEEE 802.11b, IEEE 802.11g, IEEE 802.11n crimped connections to terminate Cat5 media with RJ-45 plugs to make patch cables, and the use of punched down connections on 110 patch panels and RJ-45 jacks Insulation cut back to far and wires untwisted too much damaging voltage levels may be applied between interconnected devices Misalignment - the fiber-optic media are not precisely aligned to one another when joined. End gap - the media do not completely touch at the splice or connection. End finish - the media ends are not well polished or dirt is present at the termination.