Building a Simple Network - Study Notes

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Identify the major components of a computer system; define basic computer and networking terminology; describe the benefits and functions of the computer network.

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Building a Simple Network - Study Notes

  1. 1. Building a Simple IT Network Study Notes for +W Series - Technology Skills For Women1 http://SlideShare.net/OxfordCambridge 1 Men too are allowed to read, if they wish, as the language style and the document format are universal.
  2. 2. Study Notes http://SlideShare.net/OxfordCambridge 2 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Contents About “+W Series - Technology Skills For Women” ................................................................................ 5 A. Application sharing through networks.................................................................................................... 6 1. Major components of a computer system.......................................................................................... 6 Question ................................................................................................................................................ 10 Quiz........................................................................................................................................................ 11 2. Network interface card...................................................................................................................... 12 Quiz........................................................................................................................................................ 13 Quiz........................................................................................................................................................ 14 Summary................................................................................................................................................ 15 B. Understanding binary basics ................................................................................................................. 16 1. Bits, bytes and measurement terms ................................................................................................. 16 Quiz........................................................................................................................................................ 19 2. Conversion between decimal and binary.......................................................................................... 20 Quiz........................................................................................................................................................ 22 Quiz........................................................................................................................................................ 24 3. Conversion between binary and hexadecimal .................................................................................. 24 Quiz........................................................................................................................................................ 28 Quiz........................................................................................................................................................ 30 Summary................................................................................................................................................ 30 C. Using a PC on a network........................................................................................................................ 31 1. Basic Networking Terminology.......................................................................................................... 31 2. Network Applications ........................................................................................................................ 32 3. Computer Networks .......................................................................................................................... 34 Summary................................................................................................................................................ 36 D. Working with PC technology ................................................................................................................. 37 1. Exercise overview .............................................................................................................................. 37 2. Task 1: Identifying PC components ................................................................................................... 37 Step 1 of 1.................................................................................................................................................. 38 Result......................................................................................................................................................... 38 3. Task 2: Interpreting numerical systems ............................................................................................ 39 Step 1 of 5.............................................................................................................................................. 39 Result..................................................................................................................................................... 39 Step 2 of 5.............................................................................................................................................. 40 Result..................................................................................................................................................... 40 Step 3 of 5.............................................................................................................................................. 40
  3. 3. Study Notes http://SlideShare.net/OxfordCambridge 3 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Result..................................................................................................................................................... 40 Step 4 of 5.............................................................................................................................................. 41 Result..................................................................................................................................................... 41 Step 5 of 5.............................................................................................................................................. 41 Result..................................................................................................................................................... 41 E. OSI model layers and functions............................................................................................................. 42 1. Origins of the OSI reference model................................................................................................... 42 Quiz............................................................................................................................................................ 44 Answer....................................................................................................................................................... 44 2. OSI layers and functions.................................................................................................................... 45 Quiz............................................................................................................................................................ 50 Answer....................................................................................................................................................... 51 3. Data communications........................................................................................................................ 51 Quiz............................................................................................................................................................ 53 Answer....................................................................................................................................................... 54 Quiz............................................................................................................................................................ 58 Answer....................................................................................................................................................... 58 4. The TCP/IP protocol stack.................................................................................................................. 58 Quiz............................................................................................................................................................ 60 Answer....................................................................................................................................................... 60 Summary................................................................................................................................................ 60 F. Working with the OSI model ................................................................................................................. 62 Exercise overview.................................................................................................................................. 62 Task1: Networking terms and functions................................................................................................ 62 Result..................................................................................................................................................... 62 Step 2 of 3.............................................................................................................................................. 63 Result..................................................................................................................................................... 63 Step 3 of 3.............................................................................................................................................. 64 Result..................................................................................................................................................... 64 Task 2: Functions of the OSI model....................................................................................................... 64 1 of 1...................................................................................................................................................... 65 Result......................................................................................................................................................... 65 Task 3: The data encapsulation process................................................................................................ 65 Step 1 of 1.............................................................................................................................................. 66 Result..................................................................................................................................................... 66 G. Glossary ................................................................................................................................................. 67
  4. 4. Study Notes http://SlideShare.net/OxfordCambridge 4 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k H. Quizzes’ Answers................................................................................................................................... 96
  5. 5. Study Notes http://SlideShare.net/OxfordCambridge 5 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k About “+W Series - Technology Skills For Women” Study Notes in the field of technology will be put together under this category for the following reasons:  to encourage ladies, who wish to do so, to stand up and look over the fence into technology related topics;  with apprehension or fear;  and perhaps consider embracing a career move into this technological path;  or simply as to broaden their general knowledge; after all ICT is in most aspects of everyday life;  no matter the decision, their skills, professional strengths, and contribution can only be something positive for technical and technological fields.
  6. 6. Study Notes http://SlideShare.net/OxfordCambridge 6 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Building a Simple Network A. Application sharing through networks B. Understanding binary basics C. Using a PC on a network D. Working with PC technology E. OSI model layers and functions F. Working with the OSI model A. Application sharing through networks After completing this topic, you should be able to identify the major components of a computer system and their functionality, and list the resources required to install a NIC. 1. Major components of a computer system 2. Network interface card Summary 1. Major components of a computer system There are several fundamental elements involved in the networking of computers, including computers themselves and their components that are designed for network connectivity, as well as other network devices, such as bridges, hubs, and routers.
  7. 7. Study Notes http://SlideShare.net/OxfordCambridge 7 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Some of the major hardware elements of computers that allow network connectivity include the central processing unit (CPU), the bus, drives, memory components, ports, and cards. Many networking devices are special-purpose computers and have many of the same parts as normal PCs. For you to be able to use the computer as a reliable means of obtaining information, it must be in good working order. If the need arises to troubleshoot a simple hardware or software problem, you should be able to recognize, name, and state the purpose of PC components.  Drives  CPU  Expansion slots  Bus  Backplane components  Motherboard Drives There are different drive types – for example the CD-ROM drive, the floppy disk drive, and the hard disk drive. The CD-ROM drive is a compact disc read-only memory drive that can read information from a CD- ROM (combined CD-ROM/DVD-ROM are used nowadays). The floppy disk drive is a disk drive that can read and write to floppy disks (rarely used nowadays). The hard disk drive is the device that reads and writes data on a hard disk. CPU The CPU is the "brain" of the computer, where most of the calculations take place. The microprocessor is a silicon chip contained within a CPU.
  8. 8. Study Notes http://SlideShare.net/OxfordCambridge 8 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Expansion slots The expansion slots are openings in a computer into which you can insert a circuit board to add new capabilities to the computer. The expansion card is a printed circuit board that provides added capabilities to the computer. Bus A bus is a collection of wires through which data is transmitted from one part of a computer to another. The bus connects all the internal computer components to the CPU. The Industry-Standard Architecture (ISA) and the Peripheral Component Interconnect (PCI) are two types of buses. Backplane components The backplane is an area of the computer into which you plug external devices.
  9. 9. Study Notes http://SlideShare.net/OxfordCambridge 9 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k The following items are backplane components of a PC: - interface - mouse port - network card - parallel port - power cord - serial port - sound card - video card The interface is a piece of hardware, such as a modem connector, that allows two devices to be connected together. The mouse port is a port that is designed for connecting a mouse to a PC. The network card is an expansion board inserted into a computer to enable connection to a network. The parallel port is an interface capable of transferring more than one bit simultaneously, and is used for connecting external devices, such as printers. The power cord is a cord connecting an electrical device to an electrical outlet to provide power to the device. The serial port is an interface that can be used for serial communication in which only one bit is transmitted at a time. The sound card is an expansion board that handles sound functions. The video card is a board that plugs into a PC to give it display capabilities. Motherboard The motherboard is the main circuit board of a computer.
  10. 10. Study Notes http://SlideShare.net/OxfordCambridge 10 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k The motherboard utilizes the following primary components: - power supply - printed circuit board (PCB) - random access memory (RAM) - read-only memory (ROM) - system unit The power supply is the component that supplies power to a computer. The printed circuit board (PCB) is a thin plate on which chips (integrated circuits) and other electronic components are placed. Random access memory (RAM) is memory that has new data written into it as well as stored data read from it. It is also known as read-write memory. A drawback of RAM is that it requires electrical power to maintain data storage. If the computer is turned off or loses power, all data stored in RAM is lost unless the data was previously saved to disk. The read-only memory (ROM) is the computer memory on which data has been pre-recorded. The system unit is the main part of a PC. It is a term that encompasses the chassis, the microprocessor, the main memory, the bus, and the ports. The system unit does not include the keyboard, the monitor, or any other external devices connected to the computer. Because computers are important building blocks in a network, you should be able to identify their major components. Questioni Match the PC components to their descriptions.
  11. 11. Study Notes http://SlideShare.net/OxfordCambridge 11 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Options: 1. Backplane 2. Bus 3. CPU 4. Expansion slots 5. Floppy drive (rarely used nowadays). Targets: a. A disk drive that can read and write to floppy disks b. A part of the computer that allows external devices to be connected c. Where most of the calculations take place d. Connects all the internal computer components to the CPU e. Openings in a computer into which you can insert a circuit board Laptop computers and notebook computers have become very popular. There are few differences between the two. The main difference between PCs and laptops is that laptop components are smaller than those found in a PC, they are designed to fit together into a smaller physical space, and they use less power when operated. These smaller components can be difficult to remove. In a laptop, the expansion slots become Personal Computer Memory Card International Association (PCMCIA) card slots, or PC slots, through which NICs, modems, hard drives, and other useful devices (usually the size of a thick credit card) are connected. PCs are more powerful than laptops, but laptops have the advantage of being portable, which makes it more convenient to work from home and while traveling between offices. Quizii What are the main differences between the components of a desktop PC and a laptop? Options: 1. It is easier to remove the components from a laptop than the components from a PC 2. Laptops use less power than PCs 3. Laptop components are smaller than those in a PC 4. The slots you connect devices to are called expansion slots in a PC and PCMCIA slots in a laptop
  12. 12. Study Notes http://SlideShare.net/OxfordCambridge 12 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k 2. Network interface card A network interface card (NIC) is a printed circuit board that provides network communication capabilities to and from a personal computer. Also called a LAN adapter, the NIC plugs into a motherboard and provides a port for connecting to the network. The NIC constitutes the computer interface with the local area network (LAN). The NIC communicates with the network through a serial connection, and with the computer through a parallel connection. When a NIC is installed in a computer, it requires an interrupt request line (IRQ), an input/output (I/O) address, a memory space for the operating system (such Windows), and drivers in order to perform its function. An IRQ is a signal that informs a CPU that an event needing its attention has occurred. An IRQ is sent over a bus line to the microprocessor. An example of an interrupt request being issued is when a key is pressed on a keyboard, and the CPU must move the character from the keyboard to RAM.
  13. 13. Study Notes http://SlideShare.net/OxfordCambridge 13 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k An I/O address is a location in memory used by an auxiliary device to enter or retrieve data from a computer. When selecting a NIC for a network, you should consider the following:  type of network  type of media  type of expansion slot type of network You must choose a NIC to suit the type of network you have. Ethernet NICs are designed for Ethernet LANs. type of media The type of port or connector used by the NIC for network connection is specific to the type of media, such as twisted-pair. type of expansion slot With regard to the type of expansion slot to use, you should consider that because PCI slots are faster than ISA slots, the latter are being phased out. Quiziii Which of the following should you take into account when selecting a NIC for a network? Options: 1. The type of CPU 2. The type of media 3. The type of network 4. The type of expansion slot The ability to install a NIC correctly is an important aspect of preparing a computer for network connectivity.
  14. 14. Study Notes http://SlideShare.net/OxfordCambridge 14 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k To install a NIC, you must know about the following:  Network card configuration  Network card diagnostics  Hardware resource conflicts Network card configuration You must know how the network card is configured, including jumpers, "plug-and-play" software, and erasable programmable read-only memory (EPROM). Network card diagnostics You must know the network card diagnostics, including the vendor-supplied diagnostics and loopback tests (see the documentation that comes with the card). Hardware resource conflicts You must know how to resolve hardware resource conflicts, including IRQ, I/O base address, and direct memory access (DMA), which is used to transfer data from RAM to a device without going through the CPU. Quiziv Which options correctly describe the information needed to install a NIC? Options: 1. Knowledge of how to resolve hardware resource conflicts 2. Knowledge of all types of network cards 3. Knowledge of how the network card is configured 4. Knowledge of how to use the network card diagnostics
  15. 15. Study Notes http://SlideShare.net/OxfordCambridge 15 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Summary There are several PC components, which include the motherboard, the backplane, the central processing unit (CPU), the bus, drives, expansion slots, memory components, ports, and cards. A laptop is a portable PC that uses smaller components, is more power efficient than a PC, and has Personal Computer Memory Card International Association (PCMCIA) card slots instead of expansion slots. A network interface card (NIC) is a circuit board that allows a personal computer to communicate with a network. You need to consider the type of network, media, and expansion slot when selecting a NIC. To install a NIC, you should know how to configure it, how to use its diagnostics, and be able to resolve hardware resource conflicts.
  16. 16. Study Notes http://SlideShare.net/OxfordCambridge 16 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k B. Understanding binary basics After completing this topic, you should be able to distinguish between the processes used to convert between decimal, binary, and hexadecimal numbering systems. 1. Bits, bytes and measurement terms 2. Conversion between decimal and binary 3. Conversion between binary and hexadecimal Summary 1. Bits, bytes and measurement terms At the most basic level, computers perform their computations by using 1s and 0s instead of the decimal system. Computers are made up of electronic switches. At the lowest levels of computation, computers depend on these electronic switches to make decisions. Computers react only to electrical impulses, understood by the computer as either "on" or "off" states (1s or 0s). Computers can understand and process only data that is in a binary format, represented by 0s and 1s. These 0s and 1s represent the two possible states of an electrical impulse and are referred to as binary digits (bits). Most computer coding schemes use eight bits to represent a number, letter, or symbol. A series of eight bits is referred to as a byte. One byte represents a single addressable storage location.
  17. 17. Study Notes http://SlideShare.net/OxfordCambridge 17 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k The following are commonly used computer measurement terms:  Bit (b)  Byte (B)  Kilobit (Kb)  Kilobyte (KB)  Megabit (Mb)  Megabyte (MB)  Gigabit (Gb)  Gigabyte (GB) Bit (b) A bit is the smallest unit of data in a computer. A bit equals 1 or 0 in the binary format in which data is processed by computers. Bits per second (bps) is a standard unit of measurement for data transmission. Byte (B) A byte is a unit of measure used to describe the size of a data file, the amount of space on a disk or other storage medium, or the amount of data being sent over a network. One byte equals eight bits of data. Bytes per second (Bps) is a standard unit of measurement of the data transmission rate over a network connection. Kilobit (Kb) A kilobit is approximately 1000 bits (1024 bits exactly). Kilobits per second (Kbps) is a standard unit of measurement of the data transmission rate over a network connection.
  18. 18. Study Notes http://SlideShare.net/OxfordCambridge 18 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Kilobyte (KB) A kilobyte is approximately 1000 bytes (1024 bytes exactly). Kilobytes per second (KBps) is another standard unit of measurement for data transmission. Megabit (Mb) A megabit is approximately 1 million bits. Megabits per second (Mbps) is a standard unit of measurement of the data transmission rate over a network connection. Megabyte (MB) A megabyte is approximately 1 million bytes (1,048,576 bytes exactly). A megabyte is sometimes referred to as a "meg." Megabytes per second (MBps) is a standard unit of measurement for data transmission. Gigabit (Gb) A gigabit is equal to approximately one billion bits. Gigabits per second (Gbps) is a standard unit of measurement of the data transmission rate over a network connection. Gigabyte (GB) A gigabyte is equal to approximately one billion bytes. Gigabytes per second (GBps) is a standard unit of measurement for data transmission. It is a common error to confuse KB with Kb and MB with Mb. You should remember to do the proper calculations when comparing transmission speeds that are measured in KBps and those measured in Kbps. For example, modem software usually shows the connection speed in kilobits per second (for example, 45 Kbps). However, popular browsers display file-download speeds in kilobytes per second, meaning that with a 45-Kbps connection, the download speed would be a maximum of 5.76 KBps. In practice, this download speed cannot be reached because of other factors consuming bandwidth at the same time. The following are speed measurement terms commonly used for microprocessors:  Hz  MHz
  19. 19. Study Notes http://SlideShare.net/OxfordCambridge 19 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k  GHz Hz A hertz (hz) is a unit of frequency. It is the rate of change in the state or cycle in a sound wave, alternating current, or other cyclical waveform. It represents one cycle per second and is used to describe the speed of a computer microprocessor. MHz A megahertz (MHz) represents one million cycles per second. This is a common unit of measurement of the speed of a processing chip, such as a computer microprocessor. GHz A gigahertz (GHz) represents one billion (1,000,000,000) cycles per second. This is a common unit of measurement of the speed of a processing chip, such as a computer microprocessor. PC processors are getting faster all the time. The microprocessors used on PCs in the 1980s typically ran under 10 MHz (the original IBM PC was 4.77 MHz). Today they are measured in GHz. Quizv Match the measurement terms with their definitions. Options: 1. Bit 2. Byte 3. GB 4. KB 5. Mb 6. MB Targets: a. It equals 1 or 0 in binary format b. It is equal to 8 bits c. It is equal to approximately 1000 bytes d. It is equal to approximately one billion bytes e. It is equal to approximately one million bits f. It is equal to approximately one million bytes
  20. 20. Study Notes http://SlideShare.net/OxfordCambridge 20 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k 2. Conversion between decimal and binary Converting a decimal number to a binary number is one of the most common procedures performed in computer operations. Computers recognize and process data using the binary, or base 2, numbering system. The binary numbering system uses only two symbols (0 and 1) instead of the ten symbols used in the decimal numbering system. The position, or place, of each digit represents the number 2 (the base number) raised to a power (exponent), based on its position (2^0, 2^1, 2^2, 2^3, 2^4, and so on). Suppose you want to convert the decimal number 253 to a binary number. You can do this by dividing the number by two each time and taking note of the remaining number. First you divide 253 by 2, which is equal to 126 with 1 remaining.
  21. 21. Study Notes http://SlideShare.net/OxfordCambridge 21 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Then you divide 126 by 2, which is equal to 63 with 0 remaining. Then you divide 63 by 2, which is equal to 31 with 1 remaining. Then you divide 31 by 2, which is equal to 15 with 1 remaining. Then you divide 15 by 2, which is equal to 7 with 1 remaining. Then you divide 7 by 2, which is equal to 3 with 1 remaining. Then you divide 3 by 2, which is equal to 1 with 1 remaining. Finally you divide 1 by 2, which is equal to 0 with 1 remaining. You should write the binary number in the order of the last bit first. In this case, the binary equivalent of 253 is 11111101. Suppose you want to convert the decimal number 153 to binary. Suppose you want to convert the number 35 to a binary number. You can do this using the following steps:  Step 1  Step 2  Step 3  Step 4  Step 5 Step 1
  22. 22. Study Notes http://SlideShare.net/OxfordCambridge 22 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Step 1: Looking at the figure, you must identify what is the greatest power of 2 that is less than or equal to 35. Starting with the largest number, 2^5 (32) is smaller than 35. You place a "1" in that column, a "0" in each preceding place, and calculate how much is left over by subtracting 32 from 35. The result is 3. Step 2 Step 2: Next you check to see if 16 (the next lower power of 2) fits into 3. Because it does not, a "0" is placed in that column. The value of the next number is 8, which is larger than 3, so a "0" is placed in that column too. Step 3 Step 3: The next value is 4, which is still larger than 3, so it too receives a "0." Step 4 Step 4: The next value is 2, which is smaller than 3. Because 2 fits into 3, place a "1" in that column. Now subtract 2 from 3, and the result is 1. Step 5 Step 5: The value of the last number is 1, which fits in the remaining number. Therefore, you place a "1" in the last column. The binary equivalent of the decimal number 35 is 100011. In this case, the place values of 128 and 64 are too high to be considered for the calculation. Quizvi Which number is the binary equivalent of 197? Options: 1. 10000101 2. 10100101 3. 11000101 4. 11100101 You can also convert binary numbers to decimal format.
  23. 23. Study Notes http://SlideShare.net/OxfordCambridge 23 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k As with decimal-to-binary conversion, there is usually more than one way to convert binary numbers to decimal numbers. The figure illustrates one conversion method. Each binary digit has a corresponding decimal position value. To work out the decimal position values, you start with 1 and then multiply each number by 2. For example, 1 multiplied by 2 is equal to 2, 2 multiplied by 2 is 4, 4 multiplied by 2 is 8, and so on. Consider the 8 digits that make up the binary number. If a digit is 1, then you count the corresponding position value whereas if the digit is 0, then you ignore it. Next, suppose you want to convert the binary number 10111001 to a decimal number. You can do this using the following steps:  Step 1  Step 2  Step 3  Step 4  Step 5
  24. 24. Study Notes http://SlideShare.net/OxfordCambridge 24 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Step 1 Step 1: The binary number has a 1 in the 2^7 (128) bit position, so 128 is added to the decimal total. Step 2 Step 2: Next the binary number has a 0 in the 2^6 (64) bit position so 64 is not added to the decimal total (128+0=128). Next there is a 1 in the 2^5 (32) bit position, so the decimal total becomes 128+32=160. Step 3 Step 3: Next there is a 1 in the 2^4 (16) bit position. Adding the value to the decimal total gives 160+16=176. Then the 2^3 (8) bit position has the binary digit 1, so the value 8 needs to be added to the decimal total: 176+8=184. Step 4 Step 4: Next there are 0s in the 2^2 and 2^1 bit positions, so you add 0s to the decimal total: 184+0+0=184. Step 5 Step 5: Finally, there is a 1 in the 2^0 (1) bit position, so you add 1 to 184 to give the result 185. The decimal equivalent of the binary number 10111001 is 185. Quizvii Convert the binary number 11011000 to decimal. 3. Conversion between binary and hexadecimal The base 16, or hexadecimal (hex), numbering system is used frequently when working with computers because it can be used to represent binary numbers in a more readable form. The computer performs computations in binary, but there are instances when the binary output of a computer is expressed in hexadecimal format to make it easier to read.
  25. 25. Study Notes http://SlideShare.net/OxfordCambridge 25 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Converting a hexadecimal number to binary, and vice versa, is a common task when dealing with the 16-bit configuration register in Cisco routers. That 16-bit binary number can be represented as a four-digit hexadecimal number. For example, 0010000100000010 in binary is equal to 2102 in hex. The most common way for computers and software to express hexadecimal output is using "0x" in front of the hexadecimal number. Thus, whenever you see "0x," you know that the number that follows is a hexadecimal number. For example, 0x1234 means 1234 in base 16. It is referred to as base 16 because it uses 16 symbols. Combinations of these symbols can represent all possible numbers. Because there are only 10 symbols that represent digits (0, 1, 2, 3, 4, 5, 6, 7, 8, 9) and base 16 requires six more symbols, the extra symbols are the letters A, B, C, D, E, and F. The "A" represents the decimal number 10, "B" represents 11, "C" represents 12, "D" represents 13, "E" represents 14, and "F" represents 15.
  26. 26. Study Notes http://SlideShare.net/OxfordCambridge 26 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k The position of each symbol (digit) in a hex number represents the base number 16 raised to a power (exponent) based on its position. Moving from right to left, the first position represents 16^0 (or 1), the second position represents 16^1 (or 16), the third position represents 16^2 (or 256), and so on. Network layer 2 MAC addresses are typically written in hex. For Ethernet and Token Ring topologies, these addresses are 48 bits, or six octets (one octet is eight bits). Because these addresses consist of six distinct octets, you can write them as 12 hex numbers. Instead of writing 10101010.11110000.11000001.11100010.011101 11.01010001 you can write the much shorter hex equivalent: AA.F0.C1.E2.77.51. To make handling hex versions of MAC addresses even easier, the dots are placed only after each four hex digits, as in AAF0.C1E2.7751. Converting binary to hex is easy because base 16 (hexadecimal) is a power of base 2 (binary). Every four binary digits (bits) are equal to one hexadecimal digit. The table compares the binary and hexadecimal numbering systems.
  27. 27. Study Notes http://SlideShare.net/OxfordCambridge 27 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k If there is a binary number that looks like 01011011, you can break it into two groups of four bits: 0101 and 1011. When converting these two groups to hex, they become 5 and B, so the hexadecimal equivalent of the binary 01011011 is 5B. No matter how large the binary number, you always apply the same conversion. First you start from the right of the binary number and break the number into groups of four. If the far left group does not contain four digits, add zeros to the left end until there are four digits (bits) in every group. Then you convert each group of four to its hex equivalent. Suppose you want to convert the binary number 01001110000100110101011110001101 to hexadecimal.
  28. 28. Study Notes http://SlideShare.net/OxfordCambridge 28 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Quizviii Which options are hexadecimal equivalents of 1010110100010011111000111101100? Options: 1. 1451880940 2. 5689F1EC 3. AD13E3D4 4. 0x5689F1EC You can also convert hexadecimal numbers to binary format. To convert from hexadecimal to binary, you convert every hex digit into four binary digits (bits). For example, to convert hex AC (0xAC) to binary, you first convert hex A, which is 1010 binary, and then convert hex C, which is 1100 binary. So the conversion of hex AC is 10101100 binary.
  29. 29. Study Notes http://SlideShare.net/OxfordCambridge 29 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Suppose you want to convert the hexadecimal number 1245F7DC9 to binary. Make sure you include four binary digits for each hexadecimal character, adding zeros to the left of the number when necessary.
  30. 30. Study Notes http://SlideShare.net/OxfordCambridge 30 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Quizix Match the binary numbers to their hexadecimal equivalent. Options: 1. 1100011101011000010 2. 10101101110110101000101 3. 10100101010110001000101000100100011 4. 1011000100111111110 Targets: a. 52AC45123 b. 56ED45 c. 589FE d. 63AC2 Summary The binary numbering system is made up of 0s and 1s. The most common measurement terms are bit, byte, kilobit (Kb), kilobyte (KB), megabit (Mb), megabyte (MB), gigabit (Gb), and gigabyte (GB). The microprocessor speeds are hertz (Hz), megahertz (MHz), and gigahertz (GHz). The decimal numbering system uses ten symbols – 0 - 9. Decimal numbers can be converted to binary. One way of doing this is to divide the decimal number by two each time, taking note of the remaining number. All the remaining numbers form the binary equivalent. You can also convert binary numbers to decimal. The hexadecimal numbering system uses 16 symbols – 0 - 9, and A - F. Hexadecimal numbers often have 0x in front of them. You can easily convert binary numbers to hexadecimal as each group of four binary digits is equal to one hexadecimal digit. You can also convert hexadecimal numbers to binary by converting every hex digit into four binary digits (bits).
  31. 31. Study Notes http://SlideShare.net/OxfordCambridge 31 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k C. Using a PC on a network To review basic networking technologies and common network applications, and identify the main purposes and functions of networking. 1. Basic Networking Terminology 2. Network Applications 3. Computer Networks Summary 1. Basic Networking Terminology Computer networking, like most industries, has its own jargon, which includes technical terms, abbreviations, and acronyms. Without a good grasp of the terminology, it will be difficult to understand the concepts and processes involved in networking. The following list of terms and their definitions is intended to be a quick reference that defines some of the most important words, phrases, and acronyms related to computer networking:  A network interface card (NIC), pronounced "nick," is also called the LAN adapter, or just the network interface. This card typically goes into an ISA, PCI, or PCMCIA (PC card) slot in a computer and connects to the network medium. It then connects to other computers through the network media.  Media refers to the various physical environments through which transmission signals pass. Common network media include twisted-pair, coaxial, and fiber-optic cable, and even the earth's atmosphere through which wireless transmission occurs.  A protocol is a set of rules. In the case of a network protocol, it is a set of rules by which computers communicate. The term "protocol suite" describes a set of several protocols that perform different functions related to different aspects of the communication process.  Cisco IOS software which runs on Cisco equipment and devices, is the industry-leading and most widely deployed network system software. It delivers intelligent network services for enabling the rapid deployment of Internet applications. Cisco IOS software provides a wide range of functionality, from basic connectivity, security, and network management to technically advanced services. The functionality of Cisco IOS software is the result of a technological evolution. First-generation networking devices could only store and forward data packets. Today, Cisco IOS software can recognize, classify, and prioritize network traffic, optimize routing, support voice and video applications, and much more. Cisco IOS software runs on most Cisco routers and Cisco switches. These network devices carry most of the Internet traffic today.  Network operating system (NOS) usually refers to server software such as Windows NT, Windows 2000 Server, Windows Server 2003, Novell NetWare, UNIX, and Linux. The term sometimes refers to the networking components of a client operating system such as Windows 95 or the Macintosh OS.  Connectivity devices refer to several different device types, all of which are used to connect cable segments, connect two or more smaller networks (or subnets) into a larger network, or divide a large network into smaller ones. The term encompasses repeaters, hubs, switches, bridges, and routers.
  32. 32. Study Notes http://SlideShare.net/OxfordCambridge 32 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k The following are three categories of networks:  A local-area network (LAN) is a network that is confined to a limited geographic area. This area can be a room, a floor, a building, or even an entire campus.  A metropolitan-area network (MAN) is a network that is larger in size than a LAN and smaller in size than a WAN. This is a network that covers approximately the area of a large city or metropolitan area.  A wide-area network (WAN) is made up of interconnected LANs. It spans wide geographic areas by using WAN links such as telephone lines or satellite technology to connect computers in different cities, countries, or even different continents. Network structure is described in the following two ways:  The logical topology is the path that the signals take from one computer to another. The logical topology may or may not correspond to the physical topology. For instance, a network can be a physical "star," in which each computer connects to a central hub, but inside the hub the data can travel in a circle, making it a logical "ring."  The physical topology refers to the layout or physical shape of the network, and includes the topologies in this table. Topologies Bus Computers arranged so that cabling goes from one to another in a linear fashion Ring When there are no clear beginning points or endpoints within a topology, forming a circle Star If the systems "meet in the middle" by connecting to a central hub Mesh When multiple redundant connections make pathways to some or all of the endpoints 2. Network Applications Network applications are software programs that run between different computers connected together on a network. Some of the more common uses of network applications include using a web browser program to find content from the World Wide Web, or using an e-mail program to send e-mails over the Internet.
  33. 33. Study Notes http://SlideShare.net/OxfordCambridge 33 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Network applications are selected based on the type of work that needs to be done. A complete set of application-layer programs is available to interface with the Internet. Each application program type is associated with its own application protocol. Some examples include:  HTTP is the World-Wide-Web communications protocol used to connect to web servers. Its primary function is to establish a connection with a web server and transmit HTML pages to the client browser.  Post Office Protocol 3 (POP3) is an application-layer protocol supported by e-mail programs for the retrieval of electronic mail. POP3 is a standard e-mail server commonly used on the Internet. It provides a message storage container that holds incoming e-mail until users log on and download their messages.  File Transfer Protocol (FTP) is a simple file utility program for transferring files between remote computers, which also provides for basic user authentication.  Telnet is a remote access application and protocol for connecting to remote computer consoles, which also provides for basic user authentication. Telnet is not a graphical user interface but is command-line driven or character mode only.  Simple Network Management Protocol (SNMP) is used by network management programs for monitoring the network device status and activities. It is important to emphasize that the application layer is just another protocol layer in the OSI model or TCP/IP protocol stack. The programs interface with application layer protocols. E-mail client applications, such as Microsoft Outlook, Lotus Notes, Pegasus Mail, Mozilla's Thunderbird, Eudora, KMail, all work with the POP (Post Office Protocol) and IMAP4 (Message Access Protocol) protocols. Electronic mail enables you to send messages between connected computers. The procedure for sending an e-mail document involves two separate processes – sending the e-mail to the user's post office, which is a computer running the POP3 server software, and delivering the e-mail from that post office to the user's e- mail client computer, which is the recipient. While popular protocols for retrieving mail include POP3 and IMAP4, sending mail is usually done using the SMTP protocol. A user's mailbox can be accessed in two dedicated ways. POP allows the user to download messages one at a time and only deletes them from the server after they have been successfully saved on local storage. It is possible to leave messages on the server to permit another client to access them. Alternatively, IMAP allows users to keep messages on the server, flagging them as appropriate. IMAP provides folders and sub-folders, which can be shared among different users with possibly different access rights. Another important standard supported by most email clients is MIME, which is used to send binary file email attachments. Attachments are files that are not part of the email proper, but are sent with the email.
  34. 34. Study Notes http://SlideShare.net/OxfordCambridge 34 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k The same principle is true with web browsers. The two most popular web browsers are Google Chrome, Mozilla Firefox, Internet Explorer, Opera, and Safari. The appearance of these web browser programs might be different, but they both work with the application layer HTTP protocol. 3. Computer Networks One of the primary purposes of a network is to increase productivity by linking computers and computer networks, so that people have easy access to information regardless of differences in time, place, or type of computer system. Because companies have adopted networks as part of their business strategy, they typically subdivide and map corporate networks to the corporate business structure. In the figure, the network is defined based on the grouping of employees (users) into a main office and various remote access locations. A main office is a site where everyone is connected via a LAN and where the bulk of corporate information is located. A main office can have hundreds or even thousands of people who depend on network access to do their jobs. It may have several LANs, or it may be a campus that contains several buildings. Because everyone needs access to central resources and information, it is common to see a high-speed backbone in a LAN as well as a datacentre with high-performance computers or servers and networked applications. A variety of remote access locations connect to the main office or each other using WAN services as follows:  In branch offices, smaller groups of people work and connect to each other via a LAN. To connect to the main office, these users must use WAN services such as Asymmetric digital subscriber line (ADSL). Although some corporate information may be stored at a branch office, it is more likely that branch offices have local network resources, such as printers, but have to access information directly from the main office.  A home office is where individuals are set up to work from their own home. Home office workers most likely require on-demand connections to the main office or a branch office to access information or use network resources such as file servers.  Individuals who are mobile users connect to the main office LAN when they are at the main office, at the branch office, or on the road. Their network access needs are based on where they are located. In order to understand what types of equipment and services to deploy in a network and when to deploy them, it is important to understand the business and user needs. The figure shows how to map an organization's business or user requirements to a network.
  35. 35. Study Notes http://SlideShare.net/OxfordCambridge 35 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k In this example, the business needs may require LAN connectivity within the campus to interconnect the servers and end-user PCs, and WAN connectivity to connect the campus to the remote branch office and telecommuters. The WAN connection to the remote branch office requires a permanent connection, such as a leased line, and the home office connection requires a dial-up connection, such as ADSL. Asymmetric digital subscriber line (ADSL) is a type of digital subscriber line (DSL) technology, a data communications technology that enables faster data transmission over copper telephone lines than a conventional voice band modem can provide. It does this by utilizing frequencies that are not used by a voice telephone call. A splitter, or DSL filter, allows a single telephone connection to be used for both ADSL service and voice calls at the same time. ADSL can generally only be distributed over short distances from the telephone exchange (the last mile), typically less than 4 kilometres (2 mi). At the telephone exchange the line generally terminates at a digital subscriber line access multiplexer (DSLAM) where another frequency splitter separates the voice band signal for the conventional phone network. Data carried by the ADSL are typically routed over the telephone company's data network and eventually reach a conventional Internet Protocol network. A digital subscriber line access multiplexer (DSLAM) is a network device, often located in telephone exchanges, which connects multiple customer digital subscriber line (DSL) interfaces to a high-speed digital communications channel using multiplexing techniques.
  36. 36. Study Notes http://SlideShare.net/OxfordCambridge 36 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Summary When working with computer applications, it is important that you are familiar with networking terminology. There are three categories of networks – a LAN, a MAN, and a WAN. The physical topology of a network is the physical structure of a network. The logical topology of a network is the path that signals follow through the network. Network applications are software programs that run between different computers connected on a network. Each application type has associated protocols depending on the function of the application. HTTP is used by applications that access the Internet, POP3 is used by applications that access email services, FTP is used by applications that transfer files, Telnet is used by applications that remotely access other machines, and SNMP is used by applications that monitor the operation of the network. Applications interface with protocols in the application layer of the OSI model or TCP/IP stack. By creating a computer network, you enable access between computers regardless of time, place, or type of computer system. Because networks are incorporated into the business strategy of a company, a company's network will usually replicate its business structure. Typically, a network will be subdivided to facilitate the branch, home, and main office of the company as well as its mobile users.
  37. 37. Study Notes http://SlideShare.net/OxfordCambridge 37 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k D. Working with PC technology After completing this topic, you should be able to identify the purpose of major computer components, and calculate conversions between binary, decimal, and hexadecimal numerical systems. 1. Exercise overview 2. Task 1: Identifying PC components 3. Task 2: Interpreting numerical systems 1. Exercise overview In this exercise, you're required to identify the internal components of a PC and calculate conversions between the three numerical systems – binary, decimal, and hexadecimal. This involves the following tasks:  identifying PC components  converting between numerical systems 2. Task 1: Identifying PC components Let's look at the internal components of a PC.
  38. 38. Study Notes http://SlideShare.net/OxfordCambridge 38 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Step 1 of 1 Match the PC components to their descriptions. Options: 1. CD Rom drive 2. Hard disk drive 3. RAM 4. NIC 5. CPU Targets: a. A compact disk read-only memory drive b. A device that reads and writes data on a hard disk c. An expansion board inserted into a computer to enable connection to a network d. A silicon-based microprocessor where most of the computer's calculations take place e. Memory that has new data written into it and has stored data read from it Resultx A CD Rom drive is a compact disk read-only memory drive, a hard disk drive is a device that reads and writes data on a hard disk, RAM is memory that has new data written into it and stored data read from it, a NIC is an expansion board inserted into a computer to enable connection to a network, and a CPU is a silicon-based microprocessor where most of the computer's calculations take place. A CD-ROM drive can read information from a CD-ROM disk. A hard disk drive reads data from a hard disk. Unlike a CD-ROM drive it can also write data to a disk. RAM is also known as read-write memory. The NIC plugs into a motherboard and provides a port for connecting to the network. It is also known as a LAN adapter. A CPU acts as the "brain" of the computer.
  39. 39. Study Notes http://SlideShare.net/OxfordCambridge 39 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k 3. Task 2: Interpreting numerical systems Let's look at the binary, decimal, and hexadecimal numerical systems. Step 1 of 5 Match the numerical systems to their descriptions. Options: 1. Binary 2. Decimal 3. Hexadecimal Targets: a. This system uses 16 symbols b. This system uses 10 symbols c. This system uses 2 symbols Resultxi Binary uses 2 symbols, decimal uses 10 symbols, and hexadecimal uses 16 symbols. The binary system uses 2 symbols – 0 and 1 – and is also known as base 2. The decimal system uses 10 symbols – 0 to 9 – and is also known as base 10. The hexadecimal system uses 16 symbols – 0-9, A-F – and is also known as base 16. Let's look at some binary conversions.
  40. 40. Study Notes http://SlideShare.net/OxfordCambridge 40 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Step 2 of 5 See if you can convert the binary number 10101000 to decimal. Resultxii The decimal equivalent of the binary number 10101000 is 168. Step 3 of 5 What is the hexadecimal equivalent of 100011000101111? Options: 1. 462C 2. 462D 3. 462E 4. 462F Result The hexadecimal equivalent of 100011000101111 is 462F. Option 1 is incorrect. 462C is actually the hexadecimal equivalent of 100011000101100. Option 2 is incorrect. 462D is actually the hexadecimal equivalent of 100011000101101. Option 3 is incorrect. 462E is actually the hexadecimal equivalent of 100011000101110. Option 4 is correct. 462F is the hexadecimal equivalent of 100011000101111 – 100 is 4, 0110 is 6, 0010 is 2, and 1111 is F. Let's look at a conversion from decimal to binary.
  41. 41. Study Notes http://SlideShare.net/OxfordCambridge 41 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Step 4 of 5 See if you can convert the decimal number 68 to binary. Result The decimal number 68 is 1000100 in binary. Let's look at a conversion from hexadecimal to binary. Step 5 of 5 What is the binary equivalent of 812C? Options: 1. 1000000100101011 2. 1000000100101100 3. 1000000100101101 4. 1000000100101110 Result The binary equivalent of 812C is 1000000100101100. Option 1 is incorrect. 1000000100101011 is actually the binary equivalent of 812B. Option 2 is correct. 1000000100101100 is actually the binary equivalent of 812C – 8 is 1000, 1 is 0001, 2 is 0010, and 1100 is C. Option 3 is incorrect. 1000000100101101 is actually the binary equivalent of 812D. Option 4 is incorrect. 1000000100101110 is actually the binary equivalent of 812E.
  42. 42. Study Notes http://SlideShare.net/OxfordCambridge 42 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k E. OSI model layers and functions After completing this topic, you should be able to distinguish between the OSI reference model and the TCP/IP stack. 1. Origins of the OSI reference model 2. OSI layers and functions 3. Data communications 4. The TCP/IP protocol stack Summary 1. Origins of the OSI reference model The early development of LANs, MANs, and WANs was chaotic in many ways. The early 1980s saw tremendous increases in the number and sizes of networks. As companies realized that they could save money and gain productivity by using networking technology, they added networks and expanded existing networks as rapidly as new network technologies and products were introduced. By the middle of the 1980s, companies began to experience difficulties from all the expansions they had made. It became more difficult for networks using different specifications and implementations to communicate with each other. The companies realized that they needed to move away from proprietary networking systems, those systems which are privately developed, owned, and controlled. A standard or technology may be  proprietary  open proprietary Proprietary means that one company or a small group of companies control(s) all usage of the technology. In the computer industry, proprietary is the opposite of open.
  43. 43. Study Notes http://SlideShare.net/OxfordCambridge 43 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k open Open means that free usage of the technology is available to the public. To address the problem of networks being incompatible and unable to communicate with each other, the International Organization for Standardization (ISO) researched different network schemes. As a result of this research, the ISO created a model that would help vendors create networks that would be compatible with, and operate with, other networks. The Open Systems Interconnection (OSI) reference model, released in 1984, was the descriptive scheme that the ISO had created. It provided vendors with a set of standards that ensured greater compatibility and interoperability between the various types of network technologies produced by companies around the world. Although other models exist, most network vendors today relate their products to the OSI reference model, especially when they want to educate customers on the use of their products. It is considered the best tool available for teaching people about sending and receiving data on a network. The OSI reference model has seven numbered layers, each illustrating a particular network function. This separation of networking functions is called layering.
  44. 44. Study Notes http://SlideShare.net/OxfordCambridge 44 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k The OSI reference model defines the network functions that occur at each layer. More importantly, the OSI reference model facilitates an understanding of how information travels throughout a network. In addition, the OSI reference model describes how data travels from application programs (for example, spreadsheets), through a network medium, to an application program located in another computer, even if the sender and receiver are connected using different network media. Quiz Which of the following statements about the OSI model are correct. Options: 1. It defines the network functions that occur at each layer 2. It is a conceptual framework that specifies how information travels through networks 3. It is a model that describes how data makes its way from one application program to another throughout a network 4. It was developed in order to help companies communicate with each other using proprietary network systems. Answerxiii (See Endnotes).
  45. 45. Study Notes http://SlideShare.net/OxfordCambridge 45 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k 2. OSI layers and functions The practice of moving information between computers is divided into seven techniques in the OSI reference model. Each of the seven techniques is represented by its own layer in the model. The seven layers of the OSI reference model are as follows:  Layer 7: Application layer  Layer 6: Presentation layer  Layer 5: Session layer  Layer 4: Transport layer  Layer 3: Network layer  Layer 2: Data-link layer  Layer 1: Physical layer Dividing the network into seven layers provides the following advantages:  accelerates evolution  ensures interoperable technology  facilitates modular engineering  reduces complexity  standardizes interfaces  simplifies teaching and learning accelerates evolution Layering accelerates evolution by providing for effective updates and improvements to individual components without affecting other components or having to rewrite the entire protocol. ensures interoperable technology Layering prevents changes in one layer from affecting the other layers, allowing for quicker development, and ensuring interoperable technology. facilitates modular engineering Layering allows different types of network hardware and software to communicate with each other, thereby facilitating modular engineering. reduces complexity Layering breaks network communication into smaller, simpler parts and reduces complexity. standardizes interfaces
  46. 46. Study Notes http://SlideShare.net/OxfordCambridge 46 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Layering standardizes network component interfaces to allow multiple-vendor development and support. simplifies teaching and learning Layering breaks network communication into smaller components to make learning easier, thereby simplifying teaching. Each OSI layer contains a set of functions performed by programs to enable data packets to travel from a source to a destination on a network. Now we will look at each layer in the OSI reference model. The application layer is the OSI layer that is closest to the user. This layer provides network services to the user's applications. It differs from the other layers in that it does not provide services to any other OSI layer, but rather, only to applications outside the OSI model. The application layer establishes the availability of intended communication partners and synchronizes and establishes agreement on procedures for error recovery and control of data integrity. The presentation layer ensures that the information that the application layer of one system sends out is readable by the application layer of another system. For example, a PC program communicates with another computer, one using extended binary coded decimal interchange code (EBCDIC) and the other using ASCII to represent the same characters. If necessary, the presentation layer translates between multiple data formats by using a common format.
  47. 47. Study Notes http://SlideShare.net/OxfordCambridge 47 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k The session layer establishes, manages, and terminates sessions between two communicating hosts. It provides its services to the presentation layer. The session layer also synchronizes dialogue between the presentation layers of the two hosts and manages their data exchange. For example, web servers have many users, so there are many communication processes open at a given time. It is important to keep track of which user communicates on which path. In addition to session regulation, the session layer offers provisions for efficient data transfer, class of service, and exception reporting of session layer, presentation layer, and application layer problems. The transport layer segments data from the sending host's system and reassembles the data into a data stream on the receiving host's system. For example, business users in large corporations often transfer large files from field locations to a corporate site.
  48. 48. Study Notes http://SlideShare.net/OxfordCambridge 48 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Reliable delivery of the files is important, so the transport layer will break down large files into smaller segments that are less likely to incur transmission problems. The boundary between the transport layer and the session layer can be thought of as the boundary between application protocols and data-flow protocols. Whereas the application, presentation, and session layers are concerned with application issues, the lower four layers are concerned with data transport issues. The transport layer attempts to provide a data-transport service that shields the upper layers from transport implementation details. Specifically, issues such as reliability of transport between two hosts are the concern of the transport layer. In providing communication service, the transport layer establishes, maintains, and properly terminates virtual circuits. Transport error detection and recovery and information flow control are used to provide reliable service. The network layer provides connectivity and path selection between two host systems that may be located on geographically separated networks. The growth of the Internet has increased the number of users accessing information from sites around the world, and it is the network layer that manages this connectivity.
  49. 49. Study Notes http://SlideShare.net/OxfordCambridge 49 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k The data-link layer defines how data is formatted for transmission and how access to the network is controlled. The physical layer defines the electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating the physical link between end systems. Characteristics such as voltage levels, timing of voltage changes, physical data rates, maximum transmission distances, physical connectors, and other similar attributes are defined by physical layer specifications. In summary, the functions of the layers in the OSI model are as follows:  application network services  data representation  interhost communication  end-to-end connections  data delivery
  50. 50. Study Notes http://SlideShare.net/OxfordCambridge 50 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k  media access  binary transmission application network services The application layer provides network services to any applications requiring access to the network. data representation The presentation layer handles data representation. It ensures data is readable, and formats and structures data. It also negotiates data transfer syntax for the application layer. interhost communication The session layer provides interhost communication. In doing this it establishes, manages, and terminates sessions between applications. end-to-end connections The transport layer facilitates end-to-end communications. It handles transportation issues between hosts and ensures data transport reliability. It also establishes, maintains, and terminates virtual circuits, and provides reliability through fault detection and recovery information flow control. data delivery The network layer ensures data delivery. It provides connectivity and path selection between two host systems, routes data packets and selects the best path to deliver data. media access The data-link layer provides access to the network media. It defines how data is formatted and how access to the network is controlled. binary transmission The physical layer handles binary transmission. It defines the electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating the physical link. It is responsible for transmitting the data onto the physical media. Quiz What is the function of the session layer? Options: 1. It routes data packets 2. It ensures reliable transport of data 3. It ensures received data is readable 4. It regulates communication processes
  51. 51. Study Notes http://SlideShare.net/OxfordCambridge 51 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Answerxiv (See Endnotes). 3. Data communications All communications on a network originate at a source and are sent to a destination. The information sent on a network is referred to as data or data packets. If one computer (Host A) wants to send data to another computer (Host B), the data must first be packaged by a process called encapsulation. The encapsulation process can be thought of as putting a letter inside an envelope, and then properly writing the recipient's mail address on the envelope so it can be properly delivered by the postal system. Encapsulation wraps data with the necessary protocol information before network transit. Therefore, as the data moves down through the layers of the OSI model, each OSI layer adds a header (and a trailer if applicable) to the data before passing it down to a lower layer. The headers and trailers contain control information for the network devices and receiver to ensure proper delivery of the data and to ensure that the receiver can correctly interpret the data.
  52. 52. Study Notes http://SlideShare.net/OxfordCambridge 52 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k The figure illustrates how encapsulation occurs. It shows the manner in which data travels through the layers. The following eight steps occur in order to encapsulate data:  Step 1  Step 2  Step 3  Step 4  Step 5  Step 6  Step 7  Step 8 Step 1 Step 1: The user data is sent from an application to the application layer. Step 2
  53. 53. Study Notes http://SlideShare.net/OxfordCambridge 53 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Step 2: The application layer adds the application layer header (Layer 7 header) to the user data. The Layer 7 header and the original user data become the data that is passed down to the presentation layer. Step 3 Step 3: The presentation layer adds the presentation layer header (Layer 6 header) to the data. This then becomes the data that is passed down to the session layer. Step 4 Step 4: The session layer adds the session layer header (Layer 5 header) to the data. This then becomes the data that is passed down to the transport layer. Step 5 Step 5: The transport layer adds the transport layer header (Layer 4 header) to the data. This then becomes the data that is passed down to the network layer. Step 6 Step 6:The network layer adds the network layer header (Layer 3 header) to the data. This then becomes the data that is passed down to the data-link layer. Step 7 Step 7: The data-link layer adds the data-link-layer header and trailer (Layer 2 header and trailer) to the data. A Layer 2 trailer is usually the frame check sequence (FCS), which is used by the receiver to detect whether or not the data is in error. This then becomes the data that is passed down to the physical layer. Step 8 Step 8:The physical layer then transmits the bits onto the network media. Quiz When a user sends information across a network it first traverses the application layer. Rank the layers of the OSI model in the order in which encapsulation occurs, after the application layer. Options Option Description A Data Link B Network C Physical D Presentation E Session F Transport
  54. 54. Study Notes http://SlideShare.net/OxfordCambridge 54 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Answerxv (See Endnotes). When the remote device receives a sequence of bits, the physical layer at the remote device passes the bits to the data-link layer for manipulation. The data-link layer performs the following tasks:  Task 1  Task 2  Task 3  Task 4 Task 1 Task 1: It checks the data-link trailer (the FCS) to see if the data is in error. Task 2 Task 2: If the data is in error, it may be discarded, and the data-link layer may ask for the data to be retransmitted.
  55. 55. Study Notes http://SlideShare.net/OxfordCambridge 55 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Task 3 Task 3: If the data is not in error, the data-link layer reads and interprets the control information in the data-link header. Task 4 Task 4: It strips the data-link header and trailer, and then passes the remaining data up to the network layer based on the control information in the data-link header. This process is referred to as de-encapsulation. Each subsequent layer performs a similar de-encapsulation process. Think of de-encapsulation as the process of reading the address on a letter to see if it is for you or not, and then removing the letter from the envelope if the letter is addressed to you.
  56. 56. Study Notes http://SlideShare.net/OxfordCambridge 56 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k So that data packets can travel from the source to the destination, each layer of the OSI model at the source must communicate with its peer layer at the destination. This form of communication is referred to as peer-to-peer communication. During this process, the protocols at each layer exchange information, called protocol data units (PDUs), between peer layers. Data packets on a network originate at a source and then travel to a destination. Each layer depends on the service function of the OSI layer below it. To provide this service, the lower layer uses encapsulation to put the PDU from the upper layer into its data field. It then adds whatever headers the layer needs to perform its function. As the data moves down through Layers 7 through 5 of the OSI model, additional headers are added. The grouping of data at the Layer 4 PDU is called a segment. The network layer provides a service to the transport layer, and the transport layer presents data to the internetwork subsystem. The network layer moves the data through the internetwork by encapsulating the data and attaching a header to create a packet (the Layer 3 PDU). The header contains information required to complete the transfer, such as source and destination logical addresses.
  57. 57. Study Notes http://SlideShare.net/OxfordCambridge 57 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k The data-link layer provides a service to the network layer by encapsulating the network layer packet in a frame (the Layer 2 PDU). The frame header contains the physical addresses required to complete the data-link functions, and the frame trailer contains the FCS. The physical layer provides a service to the data-link layer, encoding the data-link frame into a pattern of 1s and 0s (bits) for transmission on the medium (usually a wire) at Layer 1. Network devices such as hubs, switches, and routers work at the lower three layers. Hubs are at Layer 1 – the physical layer, switches are at Layer 2 – the data-link layer, and routers are at Layer 3 – the network layer.
  58. 58. Study Notes http://SlideShare.net/OxfordCambridge 58 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Quiz Match the communication process with its definition. Options: 1. Encapsulation 2. De-encapsulation 3. Peer-to-peer communication Targets: a. This is the process that wraps data with the necessary protocol information before network transit. b. This is the process that checks for errors, and begins the process of stripping the header and trailer from received data. c. This is the process that facilitates the communication between OSI peer layers during data transfer. Answerxvi (See Endnotes). 4. The TCP/IP protocol stack Although the OSI reference model is universally recognized, the historical and technical open standard of the Internet is the TCP/IP protocol stack. The TCP/IP protocol stack has four layers – the application layer, the transport layer, the Internet layer, and the network access layer. It is important to note that although some of the layers in the TCP/IP protocol stack have the same names as layers in the OSI model, the layers have different functions in each model. The following are the TCP/IP protocol stack layers.  Application  Transport  Internet  Network access
  59. 59. Study Notes http://SlideShare.net/OxfordCambridge 59 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Application The application layer handles high-level protocols, including issues of representation, encoding, and dialog control. The TCP/IP model combines all application-related issues into one layer and ensures that this data is properly packaged for the next layer. Transport The transport layer deals with quality-of-service issues of reliability, flow control, and error correction. One of its protocols, the Transmission Control Protocol (TCP), provides for reliable network communications. Internet The purpose of the Internet layer is to send source packets from any network on the internetwork and have them arrive at the destination, regardless of the path they took to get there. Network access The network access layer is also called the host-to-network layer. It includes the LAN and WAN protocols, and all the details in the OSI physical and data-link layers. There are similarities and differences between the TCP/IP protocol stack and the OSI reference model. The main similarities between the TCP/IP protocol stack and the OSI reference model are  application layers  packet-switched technology  transport and network layers application layers Both have application layers, though they include different services. packet-switched technology Both assume packet-switched technology, not circuit-switched. (Analog telephone calls are an example of circuit-switched.) transport and network layers
  60. 60. Study Notes http://SlideShare.net/OxfordCambridge 60 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Both have comparable transport and network layers. The main differences between the TCP/IP protocol stack and the OSI reference model are  data-link and physical layers  implementation of standards  presentation and session layers data-link and physical layers TCP/IP combines the OSI data-link and physical layers into the network access layer. implementation of standards TCP/IP protocols are the standards around which the Internet developed, so the TCP/IP protocol stack gains credibility just because of the widespread implementation of its protocols. In contrast, networks are not typically built on the OSI model, even though the OSI model is used as a guide. presentation and session layers TCP/IP combines the OSI presentation and session layers into its application layer. Quiz In the TCP/IP protocol stack, which layer deals with reliability, flow control, and error correction? Options: 1. Application 2. Internet 3. Network access 4. Transport Answerxvii (See Endnotes). Summary The advent of LANs, WANs, and MANs in the 1980s and 1990s was largely unregulated and no standard for network communication was available. As a result it became more difficult for networks using different specifications and implementations to communicate with each other. To resolve this, the ISO created and released the OSI reference model in 1984 to provide vendors with a set of standards to ensure greater compatibility and interoperability between various types of network technologies. The OSI reference model comprises seven layers – the application, presentation, session, transport, network, data-link, and physical layer. Each layer has its own function. The application layer provides network services to the user applications. The presentation layer presents the data in a format that will be understood by the receiving application. The session layer regulates the session between the communicating hosts. The transport layer ensures reliable transport of the data. The network layer routes the packets through the network. The data-link layer controls access to the network. The physical layer sends the data along the physical wire.
  61. 61. Study Notes http://SlideShare.net/OxfordCambridge 61 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Encapsulating wraps data with the necessary protocol information before sending it across the network. De- encapsulation strips the protocol information when the data is received. Each OSI layer at the source communicates with its peer layer at the destination – this is called peer-to-peer communication. The TCP/IP protocol stack has four layers – the application layer, transport layer, internet layer, and network access layer. There are both similarities and differences between the TCP/IP protocol stack and the OSI reference model. The TCP/IP protocol stack is widely implemented whereas the OSI reference model is widely used for reference.
  62. 62. Study Notes http://SlideShare.net/OxfordCambridge 62 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k F. Working with the OSI model After completing this topic, you should be able to distinguish between basic computer and networking terms, and between the principles of the OSI reference model and the TCP/IP protocol stack. Exercise overview Task1: Networking terms and functions Task 2: Functions of the OSI model Task 3: The data encapsulation process Exercise overview In this exercise, you are required to identify networking terms and functions, and the functions of the OSI reference model. You will also examine data communication methods. This involves the following tasks:  identifying networking terms and functions  defining the functions of each OSI layer  examining the data encapsulation process Task1: Networking terms and functions The topology of a network describes the layout of the wire and devices as well as the paths used by data transmissions. Match the schematic description with its function. Options: 1. Logical topology 2. Physical topology Targets: a. This defines the structure of the paths that the signals take within a network b. This describes the physical layout or structure of the network Result The logical topology is the structure of the paths that the signals take within a network and the physical topology refers to the physical layout or structure of the network.
  63. 63. Study Notes http://SlideShare.net/OxfordCambridge 63 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k The logical topology defines the structure of the paths that the signals take within a network. Although the logical topology does not have to correspond to the physical topology, it is often the same as the physical topology. The physical topology is the actual physical shape of the network. Networks can be arranged in a bus, star, ring, or mesh format. Network applications are software programs that run between different computers connected on a network. Each application type has an associated protocol depending on the function of the application. Step 2 of 3 Which application transfers files between remote computers? Options: 1. FTP 2. HTTP 3. POP3 4. SMNP Result File transfer protocol (FTP) is used to transfer files between remote computers. Option 1 is correct. FTP is a simple file utility program used for transferring files between remote computers. Option 2 is incorrect. Hypertext Transfer Protocol (HTTP) establishes a connection between a browser and a web server allowing the client to view web pages in the web browser. Option 3 is incorrect. When you send an email it is usually Post Office Protocol version 3 (POP3) that will hold the mail in a storage container until the receiver is ready to download it. Option 4 is incorrect. Simple network monitoring protocol (SNMP) is used for monitoring network device status and activities.
  64. 64. Study Notes http://SlideShare.net/OxfordCambridge 64 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k A LAN covers a smaller geographic area than a MAN or a WAN. Step 3 of 3 Home office users are most likely to connect to the main office LAN using what WAN technology? Options: 1. Frame Relay 2. ADSL 3. Leased lines 4. X.25 Result Home office users are most likely to connect to the main office LAN using an ADSL connection. Option 1 is incorrect. Frame Relay provides a permanent serial connection. Due to the cost of such connections, this is not an effective solution for home office users Option 2 is correct. An ADSL connection is a dial-up connection, and is often used by home office users to connect to a LAN. Option 3 is incorrect. A WAN connection to the remote branch office requires a permanent connection such as a leased line. Home office users will most often use a dial-up technology. Option 4 is incorrect. X.25 is an older form of permanent serial connection, not used very often in modern networks. Due to the cost of such connections, this is not an effective solution for home office users. Task 2: Functions of the OSI model The OSI reference model has seven layers, each illustrating a particular network function. This separation of networking functions is called layering.
  65. 65. Study Notes http://SlideShare.net/OxfordCambridge 65 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k 1 of 1 What layer defines voltage levels, timing of voltage changes and maximum transmission distances? Options: 1. The data-link layer 2. The network layer 3. The physical layer 4. The session layer 5. The transport layer Result The physical layer defines voltage levels, timing of voltage changes and maximum transmission distances. Option 1 is incorrect. The data-link layer controls network access and formats data before it is transmitted to ensure that it will be properly received. Option 2 is incorrect. The network layer provides connectivity and path selection for data when moving between different network locations. Option 3 is correct. The physical layer defines the hardware specifications required for end-system communications. Option 4 is incorrect. The session layer regulates the communication processes of conversations between hosts. Option 5 is incorrect. The transport layer is responsible for the reliable transfer of data between network hosts. Task 3: The data encapsulation process Data packets are packaged in a process known as encapsulation before they travel safely across a network.
  66. 66. Study Notes http://SlideShare.net/OxfordCambridge 66 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Step 1 of 1 Which of the following describes the first step of data encapsulation? Options: 1. A data-link header is stripped from the message 2. The frame is converted into binary format 3. The data-link layer checks the data-link trailer to see if the data is in error 4. The user data is sent from an application to the application layer Result The first step of data encapsulation is when the user data is sent from an application to the application layer. Option 1 is incorrect. This occurs during de-encapsulation. When a message arrives at the data-link layer, it is checked for errors. If no errors exist, it is then stripped of its data-link header and trailer, and passed on up to the network layer. Option 2 is incorrect. Conversion to binary is one of the last processes that occurs before the data frame is transmitted onto the network media. Option 3 is incorrect. The FCS trailer is checked after the data has been received from the network and has been passed from the physical layer to the data-link layer. This is actually a part of the de-encapsulation process. Option 4 is correct. When data is sent from an application for transmission on the network, the encapsulation process begins. Encapsulation begins at the application layer and wraps data with the necessary protocol information before network transit.
  67. 67. Study Notes http://SlideShare.net/OxfordCambridge 67 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k G. Glossary ABR Acronym for available bit rate. See UBR. access list List kept by Cisco routers to control access to or from the router for a number of services (for example, to prevent packets with a certain IP address from leaving a particular interface on the router). acknowledgment Notification sent from one network device to another to acknowledge that some event (for example, receipt of a message) has occurred. Sometimes abbreviated ACK. active hub Multiport device that amplifies LAN transmission signals. adapter An adapter is a physical device that allows one hardware or electronic interface to be adapted (accommodated without loss of function) to another hardware or electronic interface. In a computer, an adapter is often built into a card that can be inserted into a slot on the computer's motherboard. The card adapts information that is exchanged between the computer's microprocessor and the devices that the card supports. adaptive routing See dynamic routing. address Data structure or logical convention used to identify a unique entity, such as a particular process or network device. Address Resolution Protocol Abbreviated to ARP. administrative distance A rating of the trustworthiness of a routing information source. In Cisco routers, administrative distance is expressed as a numerical value between 0 and 255. The higher the value, the lower the trustworthiness rating. ADSL Acronym for asymmetric digital subscriber line. One of four DSL technologies. ADSL is designed to deliver more bandwidth downstream (from the central office to the customer site) than upstream. Downstream rates range from 1.5 to 9 Mbps, while upstream bandwidth ranges from 16 to 640 kbps. ADSL transmissions work at distances up to 18,000 feet (5,488 meters) over a single copper twisted pair. algorithm Well-defined rule or process for arriving at a solution to a problem. In networking, algorithms are commonly used to determine the best route for traffic from a particular source to a particular destination. American National Standards Institute See ANSI. American Standard Code for Information Interchange See ASCII ANSI Acronym for American National Standards Institute. Voluntary organization comprised of corporate, government, and other members that coordinates standards-related activities, approves U.S. national standards, and develops positions for the United States in international standards organizations. ANSI helps develop international and U.S. standards relating to, among other things, communications and networking. ANSI is a member of the IEC and the ISO. API
  68. 68. Study Notes http://SlideShare.net/OxfordCambridge 68 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Acronym for application programming interface. Specification of function-call conventions that defines an interface to a service. application layer Layer 7 of the OSI reference model. This layer provides services to application processes (such as electronic mail, file transfer, and terminal emulation) that are outside of the OSI model. The application layer identifies and establishes the availability of intended communication partners (and the resources required to connect with them), synchronizes cooperating applications, and establishes agreement on procedures for error recovery and control of data integrity. Corresponds roughly with the transaction services layer in the SNA model. application programming interface See API. ARP Acronym for Address Resolution Protocol. Internet protocol used to map an IP address to a MAC address. Defined in RFC 826. Compare with RARP. ASCII Acronym for American Standard Code for Information Interchange. 8-bit code for character representation (7 bits plus parity). asymmetric digital subscriber line Abbreviated to ADSL. asynchronous timedivision multiplexing See ATDM Asynchronous Transfer Mode See ATM. asynchronous transmission Term describing digital signals that are transmitted without precise clocking. Such signals generally have different frequencies and phase relationships. Asynchronous transmissions usually encapsulate individual characters in control bits (called start and stop bits) that designate the beginning and end of each character. ATDM Acronym for asynchronous time-division multiplexing. Method of sending information that resembles normal TDM, except that time slots are allocated as needed rather than preassigned to specific transmitters. See FDM. ATM Acronym for Asynchronous Transfer Mode. International standard for cell relay in which multiple service types (such as voice, video, or data) are conveyed in fixed-length (53-byte) cells. Fixed-length cells allow cell processing to occur in hardware, thereby reducing transit delays. ATM is designed to take advantage of high-speed transmission media such as E3, SONET, and T3. attachment unit interface See AUI. attenuation Loss of communication signal energy. attribute Configuration data that defines the characteristics of database objects such as the chassis, cards, ports, or virtual circuits of a particular device. Attributes might be preset or user-configurable. AUI Attachment unit interface. IEEE 802.3 interface between an MAU and a NIC (network interface card). The term AUI can also refer to the rear panel port to which an AUI cable might attach, such as those found on a Cisco LightStream Ethernet access card. Also called transceiver cable. autonomous system
  69. 69. Study Notes http://SlideShare.net/OxfordCambridge 69 | P a g e B u i l d i n g a S i m p l e I T N e t w o r k Collection of networks under a common administration sharing a common routing strategy. Autonomous systems are subdivided by areas. An autonomous system must be assigned a unique 16-bit number by the IANA. Sometimes abbreviated AS. back end Node or software program that provides services to a front end. Usually transparent to the user. backbone The part of a network that acts as the primary path for traffic that is most often sourced from, and destined for, other networks. backbone cabling Cabling that provides interconnections between wiring closets, wiring closets and the POP, and between buildings that are part of the same LAN. Also known as vertical cabling. backplane The backplane is a large circuit board that contains sockets for expansion cards. backward explicit congestion notification See BECN. bandwidth The difference between the highest and lowest frequencies available for network signals. The term is also used to describe the rated throughput capacity of a given network medium or protocol. baseband Characteristic of a network technology where only one carrier frequency is used. Ethernet is an example of a baseband network. Also called narrowband. Basic Rate Interface See BRI. baud Unit of signaling speed equal to the number of discrete signal elements transmitted per second. Baud is synonymous with bits per second (bps), if each signal element represents exactly 1 bit. B-channel The name for a bearer channel. DS0 time slot that carries analog voice or digital data over ISDN. In ISDN, a full-duplex, 64-kbps channel used to send user data. BECN Acronym for backward explicit congestion notification. Bit set by a Frame Relay network in frames traveling in the opposite direction of frames encountering a congested path. DTE receiving frames with the BECN bit set can request that higher-level protocols take flow control action as appropriate. Compare with FECN. BGP Acronym for Border Gateway Protocol. Interdomain routing protocol that replaces EGP. BGP exchanges reachability information with other BGP systems. It is defined by RFC 1163. BGP4 BGP Version 4. Version 4 of the predominant interdomain routing protocol used on the Internet. BGP4 supports CIDR and uses route aggregation mechanisms to reduce the size of routing tables. Bit The smallest unit of data in a computer. A bit equals 1 or 0, and is the binary format in which data is processed by computers. Border Gateway Protocol See BGP. BPDU Acronym for bridge protocol data unit. Spanning-Tree Protocol hello packet that is sent out at configurable intervals to exchange information among bridges in the network. BRI Acronym for Basic Rate Interface. ISDN interface composed of two B channels and one D channel for circuit-switched communication of voice, video, and data.

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