1. 1 Version 3 Module 2 Networking Fundamentals

2. 2 Version 3 Data Networks Data networks developed as a result of business applications that were written for microcomputers. Businesses needed a solution that would successfully address the following three problems: –How to avoid duplication of equipment and resources –How to communicate efficiently / reduce duplicate copies of files –How to set up and manage a network Businesses realized that networking technology could increase productivity while saving money.

3. 3 Version 3 Data Networks One early solution was the creation of local-area network (LAN) standards. Because LAN standards provided an open set of guidelines for creating network hardware and software, the equipment from different companies could then become compatible.

4. 4 Version 3 Networking Devices Network devices include all the devices that connect the end- user devices together to allow them to communicate. End-user devices include computers, printers, scanners, and other devices that provide services directly to the user. End-user devices that provide users with a connection to the network are also referred to as hosts. The host devices can exist without a network, but without the network the host capabilities are greatly reduced. Host devices are physically connected to the network media using a network interface card (NIC).

5. 5 Version 3 Networking Devices Network devices provide extension of cable connections, concentration of connections, conversion of data formats, and management of data transfers. Examples of devices that perform these functions are repeaters, hubs, bridges, switches, and routers.

6. 6 Version 3 Networking Devices

7. 7 Version 3 Networking Devices Repeaters A repeater is a network device used to regenerate a signal. Repeaters regenerate analog or digital signals distorted by transmission loss due to attenuation. A repeater does not perform intelligent routing.

8. 8 Version 3 Networking Devices Hubs Hubs concentrate connections. In other words, they take a group of hosts and allow the network to see them as a single unit. This is done passively, without any other effect on the data transmission. Active hubs not only concentrate hosts, but they also regenerate signals.

9. 9 Version 3 Networking Devices Bridges Bridges convert network transmission data formats as well as perform basic data transmission management. Bridges provide connections between LANs. Bridges also perform a check on the data to determine whether it should cross the bridge or not.

10. 10 Version 3 Networking Devices Workgroup Switches Workgroup switches add more intelligence to data transfer management. Not only can they determine whether data should remain on a LAN or not, but they can transfer the data only to the connection that needs that data. Another difference between a bridge and switch is that a switch does not convert data transmission formats.

11. 11 Version 3 Networking Devices Routers Routers can regenerate signals, concentrate multiple connections, convert data transmission formats, and manage data transfers. They can also connect to a WAN, which allows them to connect LANs that are separated by great distances.

12. 12 Version 3 Network Topologies Network topology defines the structure of the network. One part of the topology definition is the physical topology, which is the actual layout of the wire or media. The other part is the logical topology, which defines how the media is accessed by the hosts for sending data.

13. 13 Version 3 Physical Topologies Commonly used physical topologies

14. 14 Version 3 Physical Topologies Bus A bus topology uses a single backbone cable that is terminated at both ends. All the hosts connect directly to this backbone.

15. 15 Version 3 Physical Topologies Ring A ring topology connects one host to the next and the last host to the first. This creates a physical ring of cable.

16. 16 Version 3 Physical Topologies Star A star topology connects all cables to a central point of concentration.

17. 17 Version 3 Physical Topologies Extended Star An extended star topology links individual stars together by connecting the hubs and/or switches. This topology can extend the scope and coverage of the network.

18. 18 Version 3 Physical Topologies Hierarchical A hierarchical topology is similar to an extended star. However, instead of linking the hubs and/or switches together, the system is linked to a computer that controls the traffic on the topology.

19. 19 Version 3 Physical Topologies Mesh A mesh topology is implemented to provide as much protection as possible from interruption of service. Each host has its own connections to all other hosts.

20. 20 Version 3 Logical Topologies The logical topology of a network is how the hosts communicate across the medium. The two most common types of logical topologies are broadcast and token passing.

21. 21 Version 3 Logical Topologies Broadcast Broadcast topology simply means that each host sends its data to all other hosts on the network medium. There is no order that the stations must follow to use the network. It is first come, first serve. Ethernet works this way.

22. 22 Version 3 Logical Topologies Token Passing Token passing controls network access by passing an electronic token sequentially to each host. When a host receives the token, that host can send data on the network. If the host has no data to send, it passes the token to the next host and the process repeats itself. Two examples of networks that use token passing are Token Ring and Fiber Distributed Data Interface (FDDI).

23. 23 Version 3 Local-area Networks (LANs) LANs are designed to: –Operate within a limited geographic area –All multi-access to high-bandwidth media –Control the network privately under local administration –Provide full-time connectivity to local services –Connect physically adjacent devices LANs make it possible for businesses that use computer technology to locally share files and printers efficiently, and make internal communications possible.

24. 24 Version 3 Local-area Networks (LANs) LANs consist of the following components: –Computers –Network interface cards –Peripheral devices –Networking media –Network devices Some common LAN technologies are: –Ethernet –Token Ring –FDDI

25. 25 Version 3 Wide-area Networks (WANs) WANs interconnect LANs, which then provide access to computers or file servers in other locations. WANs are designed to: –Operate over a large geographical area –Allow access over serial interfaces operating at lower speeds –Provide full-time and part-time connectivity –Connect devices separated over wide, even global areas

26. 26 Version 3 Wide-area Networks (WANs) Some common WAN technologies are: –Modems –Integrated Services Digital Network (ISDN) –Digital Subscriber Line (DSL) –Frame Relay –US (T) and Europe (E) Carrier Series – T1, E1, T3, E3 –Synchronous Optical Network (SONET)

27. 27 Version 3 Bandwidth Bandwidth is defined as the amount of information that can flow through a network connection in a given period of time. Why bandwidth is important: –Bandwidth is limited by physics and technology (it is finite) –Bandwidth is not free –Bandwidth requirement are growing at a rapid rate –Bandwidth is critical to network performance

28. 28 Version 3 Bandwidth Analogy

29. 29 Version 3 Bandwidth Measurements In digital systems, the basic unit of bandwidth is bits per second (bps). Bandwidth is the measure of how much information, or bits, can flow from one place to another in a given amount of time, or seconds. Most common measurements

30. 30 Version 3 Bandwidth Limitations Bandwidth varies depending upon the type of media as well as the LAN and WAN technologies used. The actual bandwidth of a network is determined by a combination of the physical media and the technologies chosen for signaling and detecting network signals.

31. 31 Version 3 Data Transfer Calculation Using the formula transfer time = size of file / bandwidth (T=S/BW) allows a network administrator to estimate several of the important components of network performance. If the typical file size for a given application is known, dividing the file size by the network bandwidth yields an estimate of the fastest time that the file can be transferred. Two important points should be considered when doing this calculation. 1.The result is an estimate only, because the file size does not include any overhead added by encapsulation. 2.The result is likely to be a best-case transfer time, because available bandwidth is almost never at the theoretical maximum for the network type. A more accurate estimate can be attained if throughput is substituted for bandwidth in the equation.

32. 32 Version 3 Data Transfer Calculation Although the data transfer calculation is quite simple, one must be careful to use the same units throughout the equation. In other words, if the bandwidth is measured in megabits per second (Mbps), the file size must be in megabits (Mb), not megabytes (MB). Since file sizes are typically given in megabytes, it may be necessary to multiply the number of megabytes by eight to convert to megabits.

33. 33 Version 3 Data Transfer Calculation Formula transfer time = size of file / bandwidth Example – Approximately how long would it take to transfer a 10 Mb file over a T1 line? 10 Mb = 10,000,000 bits T1 = 1.544 Mbps or 1,544,000 bits per second 10,000,000 / 1,544,000 = 6.477 Mbps OR 10 / 1.544 = 6.477 seconds T= S BW

34. 34 Version 3 Data Transfer Calculation Formula transfer time = size of file / bandwidth Example – Approximately how long would it take to transfer a 10 MB file over a T1 line? 10 MB = 10,000,000 bytes T1 = 1.544 Mbps or 1,544,000 bits per second Convert the bytes to bits  10,000,000 X 8 = 80,000,000 bits 80,000,000 / 1,544,000 = 51.81 Mbps OR 80 / 1.544 = 51.81 seconds T= S BW

35. 35 Version 3 Data Transfer Calculation Formula transfer time = size of file / bandwidth Problem – Approximately how long would it take to transfer a 18.9 MB file over a T1 line? T= S BW

36. 36 Version 3 Layered Communication Model The information that travels on a network is generally referred to as data or a packet. A packet is a logically grouped unit of information that moves between computer systems. In order for data packets to travel from a source to a destination on a network, it is important that all the devices on the network speak the same language or protocol. A protocol is a set of rules that make communication on a network more efficient. A data communications protocol is a set of rules or an agreement that determines the format and transmission of data.

37. 37 Version 3 Layered Communication Model Layer 4 on the source computer communicates with Layer 4 on the destination computer. The rules and conventions used for this layer are known as Layer 4 protocols. It is important to remember that protocols prepare data in a linear fashion.

38. 38 Version 3 OSI Model To address the problem of network incompatibility, the International Organization for Standardization (ISO) researched networking models in order to find a generally applicable set of rules for all networks. Using this research, the ISO created a network model that helps vendors create networks that are compatible with other networks. The Open System Interconnection (OSI) reference model released in 1984 was the descriptive network model that the ISO created. It provided vendors with a set of standards that ensured greater compatibility and interoperability among various network technologies.

39. 39 Version 3 OSI Model The OSI reference model has become the primary model for network communications. Although there are other models in existence, most network vendors relate their products to the OSI reference model. Benefits of the OSI Model: –Reduces complexity –Standardizes interfaces –Accelerates evolution –Simplifies teaching and learning

40. 40 Version 3 OSI Model The OSI reference model is a framework that is used to understand how information travels throughout a network. The OSI reference model explains how packets travel through the various layers to another device on a network, even if the sender and destination have different types of network media.

41. 41 Version 3 OSI Model

42. 42 Version 3 OSI Model

43. 43 Version 3 OSI Model

44. 44 Version 3 OSI Model

45. 45 Version 3 OSI Model

46. 46 Version 3 OSI Model

47. 47 Version 3 OSI Model

48. 48 Version 3 OSI Model In order for data to 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. During this process, the protocols of each layer exchange information, called protocol data units (PDUs).

49. 49 Version 3 OSI Model 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; then it adds whatever headers and trailers the layer needs to perform its function.

50. 50 Version 3 OSI Model

51. 51 Version 3 TCP/IP Model The U.S. Department of Defense (DoD) created the TCP/IP reference model, because it wanted to design a network that could survive any conditions, including a nuclear war. TCP/IP was developed as an open standard. This meant that anyone was free to use TCP/IP.

52. 52 Version 3 TCP/IP Model The TCP/IP model has the following four layers:

53. 53 Version 3 TCP/IP Model Although some of the layers in the TCP/IP model have the same name as layers in the OSI model, the layers of the two models do not correspond exactly.

54. 54 Version 3 TCP/IP Model The figure illustrates some of the common protocols specified by the TCP/IP reference model layers.

55. 55 Version 3 Encapsulation 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 through a process called encapsulation. Encapsulation wraps data with the necessary protocol information before network transit.

56. 56 Version 3 Encapsulation Five conversion steps in order to encapsulate data: 1.Build the data – Layers 7 - 5 2.Package the data for end-to-end transport – Layer 4 3.Add the network IP address to the header – Layer 3 4.Add the data link layer header and trailer – Layer 2 5.Convert to bits for transmission – Layer 1

57. 57 Version 3 Encapsulation Segments Packets Frames Bits IP Aderess MAC Address SourceDestination