1. Topic 5 Review on fundamentals of Networking

2. NETWORKING FUNDAMENTALS

3. WHAT IS A NETWORK? A network is simply two or more computers that are linked together. The most common types of networks are: Local Area Networks (LANS) and Wide Area Networks (WANS). The primary difference between the two is that a LAN is generally confined to a limited geographical area, whereas a WAN covers a large geographical area. Most WANs are made up of several connected LANs.

4. TYPES OF NETWORKS Local Area Network (LAN) – a network that spans a small area such as a building or an office. – Software applications and other resources are stored on a file server. – Print servers enable multiple users to share the same printer. Wide Area Network (WAN) – a network that spans a wide geographical area; there are several types of WANS – Metropolitan area network (MAN) – Public access network (PAN) – Value added network (VAN) – Virtual private network (VPN)

5. TYPES OF NETWORKS Intranet – An intranet is a private LAN designed for use by everyone within an organization. An intranet might consist of an internal e- mail system, a message board and one or more Web site portals that contain company news, forms, and personnel information. Access to an intranet’s web site is restricted by a firewall. Extranet – a network that connects people within your company with people who are outside your company--all within a secure, password-protected network that can be accessed from anywhere. people who are outside your company--all within a secure, password-protected network that can be accessed from anywhere.

6. BENEFITS OF A NETWORK Information sharing: Authorized users can use other computers on the network to access and share information and data. This could include special group projects, databases, etc. Hardware sharing: One device connected to a network, such as a printer or scanner, can be shared by many users. Software sharing: Instead of purchasing and installing a software program on each computer, it can be installed on the server. All of the users can then access the program from a single location. Collaborative environment: Users can work together on group projects by combining the power and capabilities of diverse equipment.

7. RISKS OF NETWORK COMPUTING The security of a computer network is challenged everyday by: – Equipment malfunctions – System failures Note: equipment malfunctions and system failures may be caused by natural disasters such as floods, storms, or fires, and electrical disturbances – Computer hackers – Virus attacks

8. COMMUNICATIONS MEDIA Communications Channel – To transfer data from one computer to another requires some type of link through which the data can be transmitted. This link is known as the communications channel. – To send data through the channel requires some type of transmission media, which may be either physical or wireless.

9. PHYSICAL MEDIA Twisted-pair cable – consists of two independently insulated wires twisted around each other (least expensive type of cable—the kind that is used in many telephone systems) Coaxial cable – consists of an insulated center wire grounded by a shield of braided wire (the primary type of cabling used by the cable television industry; it is more expensive than twisted pair) Fiber-optic cable – contains hundreds of clear fiberglass or plastic fibers (threads) (made from thin, flexible glass tubing; bandwidth is greater, so it can carry more data; it is lighter than metal wires and is less susceptible to interference; it is fragile and expensive) ISDN line – a special digital telephone line that transmits and receives information at very high speeds

10. WIRELESS MEDIA Microwave system – transmits data via high-frequency radio signals through the atmosphere Satellite system – receive transmitted signals, amplify them, and then transmit the signals to the appropriate locations Cellular technology – uses antennae resembling telephone towers to pick up radio signals within a specific area (cell) Infrared technology – transmits data as infrared light waves from one device to another, providing wireless links between PCs and peripherals Note: The type selected is determined by the type of network, the size of the network, and the cost.

11. HOW ARE NETWORKS CATEGORIZED? Networks are usually classified using three properties: Topology Protocol Architecture

12. NETWORK TOPOLOGIES Network Topology (or layout) – refers to the way computers and peripherals are configured to form networks – Bus topology – all computers are linked by a single line of cable – Star topology – multiple computers and peripheral devices are linked to a central computer, called a host – Ring topology – each computer or workstation is connected to two other computers, with the entire network forming a circle – Hybrid topology – combine network layout types to meet their needs

13. NETWORK/COMMUNICATION PROTOCOLS A protocol is simply an agreed-on set of rules and procedures for transmitting data between two or more devices. Features determined by the protocol are: – How the sending device indicates it has finished sending the message. – How the receiving device indicates it has received the message. – The type of error checking to be used.

14. NETWORK/COMMUNICATIONS PROTOCOLS Most networks use Ethernet, but some network may use IBM’s Token Ring protocol. On the Internet, the major protocol is TCP/IP (an acronym for Transmission Control Protocol/Internet Protocol).

15. EXAMPLE OF AN ETHERNET BUS Ethernet LANs use a bus topology. All stations are connected to a single long cable. ش Any station can send a signal along the cable, which all other stations will receive. Unlike ring topologies, the cable doesn't close a loop.

16. TOKEN RING NETWORK A token passing ring LAN is a group of computers connected in a loop. The group uses a token passing access mechanism. A computer wishing to send data should first receive permission. When it gets control of the network it may transmit a frame. Each frame transmitted on the ring is transmitted from one computer to the next, until it ultimately returns to the initiator of the transmission.

17. INTERNET PROTOCOLS

18. NETWORKING HARDWARE AND SOFTWARE Hub – electronic device (with a number of ports) used in a LAN to link groups of computers Repeaters (also called amplifiers) – electronic devices that receive signals and amplify and send them along the network Routers - electronic devices used to ensure messages are sent to their intended destinations Gateway – consists of hardware and/or software that allows communications between dissimilar networks Bridge – consists of hardware and/or software that allows communication between two similar networks

19. HUBS The original Ethernet LANs relied on certain physical characteristics of the cable carrying the network data (usually coaxial cable). New Ethernet technologies introduced new cable types that we unable to fulfill the original physical requirements. New devices - hubs - were introduced to simulate those characteristics. Simply put, the hub's major function is to replicate data it receives from one device attached to it to all others.

20. REPEATERS An illustration of a repeater at work The electrical signal entering the repeater at one end is weakened. The repeater amplifies the electrical signals and resends the data. A common problem in the networking world is that of weakening electrical signals. Electrical signals traveling through wires (such as copper wires used in most networks), weaken due to the wire's electrical resistance. This effect limits the lengths of the cable that can be used. A repeater will overcome this limit, when there is a need to connect two computers at a larger distance. A repeater is connected to two cable segments. Any electrical signal reaching the repeater from one segment, will be amplified and retransmitted to the other segment.

21. ROUTERS Routers connect two or more networks and forward data packets between them. When data arrives from one of the segments, the router decides, according to it's routing table, to which segment to forward that data.

22. GATEWAY "Gateway" is a term that was once used to refer to a routing device. Today, in the TCP/IP world, the term "router" is used to describe such a device. The term gateway now refers to special-purpose devices, that perform protocol conversions. Gateways implement application layer conversions of information received from various protocols. Examples of gateways found on today's markets are: – VocalTec Gateway: A gateway that converts human speech traveling on analog phone lines into local area network protocol data, and visa-versa. VocalTec Gateway – RadVision Gateway: Converts video from digital phone lines into local area network protocol data, and visa-versa. RadVision Gateway

23. MODEMS An illustration of data sent using a modem and a regular telephone line. A modem is a device that converts digital data originating from a terminal or computer, to analog signals used by voice communication networks such as the telephone system. At one end, modems convert the digital pulses to audible tones and convert audio tones back to digital pulses at the other. The word "Modem" stands for "MOdulator-DEModulator".

24. MODEMS Transmission speed Modems are available in different transmission speeds, which are measured in BPS (bits per second) also called BAUD rate. Standard modems speeds: 9600 baud, 14400 baud, 28800 baud, 33600 baud, 56800 baud. Internal/External Internal modems are electronic cards. An internal modem is installed in one of the computer's expansion slot. External modems are fully functioning external devices. The external modem is connected to a computer using a serial cable to one of the computer's serial ports, and draws power from an external power source.

25. EXAMPLE OF FIREWALL Firewalls are systems that establish access control policies among networks. They can block information from entering a network or from getting out of that network, they can permit different users to perform different kinds of operations, according to the user's authorizations.

26. NETWORK ARCHITECTURE Network architecture – refers to the way a network is designed and built. The two major types are: – Peer-to-peer architecture – Computers connect with each other in a workgroup to share files, printers, and Internet access. This is used to connect a small number of computers. – Client/server architecture – sends information from a client computer to a server, which then relays the information back to the client computer, or to other computers on the network

27. COMMUNICATION PROTOCOLS  File transfer protocol (FTP) – used to transmit files.  Simple mail transfer protocol (SMTP) – used to transmit e-mail messages.  Post office protocol (POP) – allows the recipient to retrieve messages.  Wireless application protocol – enables wireless devices to access and use the Internet using a client/server network.  802.11 – protocol for wireless LAN technology

28. DATA TRANSMISSION CHARACTERISTICS Bandwidth (rate of transmission) Analog or Digital (type of signal) – Analog transmission – takes the form of continuous waves transmitted over a medium at a certain frequency rage – Digital transmission – sends data in the form of bits Serial or Parallel (order of bits) – Serial transmission – all of the data bits are transmitted one bit after another in a continuous line – Parallel transmission – data bits are sent at the same time along multiple paths

29. COMMUNICATIONS SOFTWARE E-Mail Software – used to send and receive electronic messages using the Internet Web Browser – allows users to access and view Web pages Groupware – allows groups of people on a network to share information and to collaborate on various projects

30. 30 There are many different devices for interconnecting networks

31. 31 Ethernet Hub Used to connect hosts to Ethernet LAN and to connect multiple Ethernet LANs Collisions are propagated

32. 32 Bridges/LAN switches A bridge or LAN switch is a device that interconnects two or more Local Area Networks (LANs) and forwards packets between these networks. Bridges/LAN switches operate at the Data Link Layer (Layer 2)

33. 33 Terminology: Bridge, LAN switch, Ethernet switch There are different terms to refer to a data-link layer interconnection device: The term bridge was coined in the early 1980s. Today, the terms LAN switch or (in the context of Ethernet) Ethernet switch are used. Convention: Since many of the concepts, configuration commands, and protocols for LAN switches were developed in the 1980s, and commonly use the old term `bridge’, we will, with few exceptions, refer to LAN switches as bridges.

34. 34 Ethernet Hubs vs. Ethernet Switches An Ethernet switch is a packet switch for Ethernet frames Buffering of frames prevents collisions. Each port is isolated and builds its own collision domain An Ethernet Hub does not perform buffering: Collisions occur if two frames arrive at the same time. HubSwitch

35. FIBER DISTRIBUTED DATA INTERFACE (FDDI)

36. 36 INTRODUCTION SHARED MEDIA NETWORK LIKE ETHERNET (IEEE 802.3) & IBM TOKEN RING (IEEE 802.5) 100 Mbps SPEED RUNS ON OPTICAL FIBER AMERICAN NATIONAL STANDARDS INSTITUTE (ANSI) STANDARD

37. 37 TIMELINE FOR FDDI PROJECT INITIATED IN OCTOBER 1982 BY JAMES HAMSTRA AT SPERRY (NOW UNISYS) TWO PROPOSALS FOR MEDIA ACCESS CONTROL (MAC) & PHYSICAL (PHY) LAYERS SUBMITTED IN JUNE 1983 FDDI MAC BECAME AN ANSI STANDARD IN LATE 1986 FDDI PHY WON ANSI STANDARDIZATION IN 1988 FDDI - II PROPOSAL WAS MADE IN EARLY 1986 FIRST PUBLIC DEMONSTRATIONS AT ADVANCED MICRO DEVICES (AMD) IN 1989

38. 38 FDDI BASIC PRINCIPLE TOKEN RING NETWORK LIKE IEEE 802.5 TOKEN: A SPECIAL SEQUENCE OF BITS TOKEN CIRCULATES AROUND THE RING A STATION REMOVES THE TOKEN FROM RING BEFORE TRANSMISSION AFTER TRANSMISSION, THE STATION RETURNS THE TOKEN TO THE RING COLLISIONS ARE PREVENTED AS THERE IS ONLY ONE TOKEN IN THE RING Token ring :: a number of stations connected by transmission links in a ring topology. Information flows in one direction along the ring from source to destination and back to source.

39. 39 TOKEN RING NETWORK

40. 40 FDDI PHYSICAL PROPERTIES DUAL-COUNTER-ROTATING TOKEN RING ARCHITECTURE ONE RING IS PRIMARY AND THE OTHER SECONDARY UP TO 500 STATIONS WITH A MAXIMUM DISTANCE OF 2 KM BETWEEN ANY PAIR OF STATIONS FOR MULTIMODE FIBER WITH SINGLE-MODE FIBER THE DISTANCE CAN BE UP TO 40 KM MAXIMUM RING LENGTH IS 100 KM (TOTAL FIBER LENGTH IS 200 KM FOR TWO RINGS) USES 4B/5B ENCODING

41. 41 FDDI DUAL RINGS FDDI DUAL RING ARCHITECTURE

42. 42 OPERATION ON FAILURE OF THE PRIMARY RING

43. 43 FDDI ARCHITECTURAL MODEL ACCORDING TO THE OSI-RM, FDDI SPECIFIES LAYER 1 (PHYSICAL LAYER) AND PART OF LAYER 2 (DATA LINK CONTROL LAYER) THE PHYSICAL LAYER HANDLES THE TRANSMISSION OF RAW BITS OVER A COMMUNICATIONS LINK THE DATA LINK CONTROL (DLC) LAYER IS RESPONSIBLE FOR MAINTAINING THE INTEGRITY OF INFORMATION EXCHANGED BETWEEN TWO POINTS

44. FDDI Layers

45. 45 THE PMD LAYER PMD LAYER DEFINES THE TYPE OF MEDIA INTERCONNECTION AND ITS CHARACTERISTICS SUCH AS TRANSMITTER POWER, FREQUENCIES, RECEIVER SENSITIVITIES, BIT ERROR RATES (BER), OPTICAL COMPONENTS ETC.

46. 46 THE PHY LAYER PROVIDES THE MEDIA INDEPENDENT FUNCTIONS ASSOCIATED WITH THE OSI PHYSICAL LAYER ALSO PROVIDES SMT THE SERVICES REQUIRED FOR THE ESTABLISHMENT AND MAINTENANCE OF THE FDDI RING (BY CONTINUOUSLY LISTENING TO THE INCOMING SIGNAL)

47. 47 THE MAC LAYER PROVIDES FAIR & DETERMINISTIC ACCESS FAIR: NO NODE HAS ADVANTAGE OVER ANOTHER IN ACCESSING THE MEDIUM DETERMINISTIC: UNDER ERROR-FREE CONDITIONS, THE TIME A NODE HAS TO WAIT TO ACCESS THE MEDIUM CAN BE PREDICTED MEDIUM ACCESS IS CONTROLLED BY A TOKEN TOKEN PERMITS THE NODE THAT RECEIVES IT TO TRANSMIT FRAMES THE MAC LAYER OF THE NODE THAT GENERATED THE FRAME IS RESPONSIBLE FOR REMOVING THE TOKEN

48. 48 THE SMT LAYER A SOPHISTICATED, BUILT-IN NETWORK MONITORING AND MANAGEMENT CAPABILITY SMT IS NOT AN OSI-RM SPECIFICATION MAKING USE OF THE SERVICES PROVIDED BY PMD, PHY, AND MAC, IT CARRIES OUT MANY FUNCTIONS SUCH AS NODE INITIALIZATION, BYPASSING FAULTY NODES, COORDINATION OF NODE INSERTION AND REMOVAL, FAULT ISOLATION AND RECOVERY SMT IS MOST COMMONLY IMPLEMENTED AS A SOFTWARE PROCESS RUNNING ON THE FDDI DEVICE

49. 49 FDDI BENEFITS HIGH BANDWIDTH (10 TIMES MORE THAN ETHERNET) LARGER DISTANCES BETWEEN FDDI NODES BECAUSE OF VERY LOW ATTENUATION (  0.3 DB/KM) IN FIBERS IMPROVED SIGNAL-TO-NOISE RATIO BECAUSE OF NO INTERFERENCE FROM EXTERNAL RADIO FREQUENCIES AND ELECTROMAGNETIC NOISE VERY DIFFICULT TO TAP SIGNALS FORM A FIBER CABLE

50. 50 FDDI LIMITATIONS HIGH COST OF OPTICAL COMPONENTS REQUIRED FOR TRANSMISSION/RECEPTION OF SIGNALS (ESPECIALLY FOR SINGLE MODE FIBER NETWORKS) MORE COMPLEX TO IMPLEMENT THAN EXISTING LOW SPEED LAN TECHNOLOGIES SUCH AS IEEE 802.3 AND IEEE 802.5

51. 51 APPLICATIONS OF FDDI OFFICE AUTOMATION AT THE DESKTOP BACKBONES FOR FACTORY AUTOMATION BACKEND DATA CENTER APPLICATIONS CAMPUS LAN INTERCONNECTION INTERCAMPUS BACKBONES OR METROPOLITAN AREA NETWORKS (MANs) INTERCONNECTION OF PRIVATE BRANCH EXCHANGES (PBXS) WORKGROUP AND DEPARTMENTAL LANS INTEGRATED TRANSPORT FOR MULTIMEDIA APPLICATIONS

52. Taxonomy of multiple-access protocols discussed in this chapter

53. RANDOM ACCESS In random access or contention methods, no station is superior to another station and none is assigned the control over another. No station permits, or does not permit, another station to send. At each instance, a station that has data to send uses a procedure defined by the protocol to make a decision on whether or not to send.

54. CONTROLLED ACCESS In controlled access, the stations consult one another to find which station has the right to send. A station cannot send unless it has been authorized by other stations. We discuss three popular controlled-access methods.

55. Fast Ethernet In computer networking, Fast Ethernet is a collective term for a number of Ethernet standards that carry traffic at the nominal rate of 100 Mbit/s, against the original Ethernet speed of 10 Mbit/s. Of the Fast Ethernet standards 100BASE-TX is by far the most common and is supported by the vast majority of Ethernet hardware currently produced. Fast Ethernet was introduced in 1995 and remained the fastest version of Ethernet for three years before being superseded by gigabit Ethernetcomputer networkingEthernetgigabit Ethernet

56. CHANNELIZATION Channelization is a multiple-access method in which the available bandwidth of a link is shared in time, frequency, or through code, between different stations. In this section, we discuss three channelization protocols. Frequency-Division Multiple Access (FDMA) Time-Division Multiple Access (TDMA) Code-Division Multiple Access (CDMA)