Ch.2 – Networking Fundamentals

1. Ch.2 – Networking Fundamentals

2. Overview Remember, we are just beginning to herd the cats. Much of this will become clearer LATER! The more we learn, the more all of this will come into focus!

3. What is Networking? Networking - the interconnection of workstations, peripherals, terminals and other devices. Whatis.com: “In information technology, networking is the construction, design, and use of network, including the physical (cabling, hub, bridge, switch, router, and so forth), the selection and use of telecommunication protocol and computer software for using and managing the network, and the establishment of operation policies and procedures related to the network.”

4. The Evolution of Data networks • Peer-to-peer: Enabling communications between two computers, without relying on a computer server (client/server). • LANs (Local Area Networks): Enabling communications between groups of computers and other devices within an office, company, etc., including servers and printers. • WANs (Wide Area Networks): Enabling communications between individual computers, computers on different LANs, etc.

5. Network Media Symbols Becoming obsolete Usually a LAN connection The Serial connection symbol usually represents some sort of WAN connection such as leased line (T1), ISDN, Frame Relay, ATM, asynchronous dial-up (modem), etc.

6. Networking devices

7. Repeaters • In the “old days”, repeaters were typically used to extend the size or length of a bus-topology network. • Repeaters take a signal in on one end and regenerate that signal out the other end. • In most networks (LANs), repeaters have been replaced by hubs, which have been mostly replaced by switches. • MORE LATER!

8. Hubs • Hubs allow computers and other network devices to communicate with each other, and use a star topology. • Like a repeater, a hub regenerates the signal. • Hubs have the same disadvantage as a repeater, anything it receives on one port, it FLOODS out all other ports. • Wherever possible, hubs should be replace by switches. • More LATER!

9. Switches • Switches look a lot like hubs, but internally are much different. • Switches can learn where devices are on the network, so they do not have flood information (frames), but can FILTER them so the information only goes out the port towards the destination device. • Switches also uses a star topology. Switch

10. Router • A router is used to separate or segment one network from another network. • This will make more sense LATER!

11. Network topologies

12. Network topologies • Network topology defines the structure of the network. • Physical topology: Actual layout of the wire or media. • Bus • Star, Extended Star • Ring • Logical topology: Defines how the media is accessed by the hosts for sending data. • Broadcast or multi-access • token passing

13. Bus Topology “A bus topology uses a single backbone segment (length of cable) that all the hosts connect to directly.”

14. Other Bus Topologies

15. In the 70’s I was usually working on my bus topology…

16. Ring Topology • “A ring topology connects one host to the next and the last host to the first. • This creates a physical ring of cable.”

17. Token Ring • Ring topologies use a token passing (logical topology). • Token Ring NIC and Hub (or MAU) • Token Ring networks are becoming obsolete and not part of this curriculum.

18. Star Topology • “A star topology connects all cables to a central point of concentration. • This point is usually a hub or switch, which will be described later in the chapter.”

19. Extended Star Topology • “An extended star topology uses the star topology to be created. • It links individual stars together by linking the hubs/switches. • This, as you will learn later, will extend the length and size of the network.”

20. Hierarchical Topology Only one definition -> “A hierarchical topology is created similar to an extended star but instead of linking the hubs/switches together, the system is linked to a computer that controls the traffic on the topology.”

21. Hierarchical Topology Another definition -> A hierarchical design or model is one that implements a layered approach to networking. This is discussed later in CCNP courses.

22. Mesh Topology • A mesh topology is used when there can be absolutely no break in communications, for example the control systems of a nuclear power plant. • Each device has its own connections to all other hosts. • This also reflects the design of the Internet, which has multiple paths to any one location.” • There are also full mesh and partial mesh topologies, both physical and logical, which will be discussed later in CCNA semester 4.

23. Full Mesh and Switched Telephone Lines

24. Network protocols • Protocol - Set of rules and conventions that govern a particular aspect of how devices on a network communicate. • Including: format, timing, sequencing, and error control in data communication. • Protocol suites are collections of protocols that enable network communication from one host through the network to another host. • Without protocols, the computer cannot make or rebuild the stream of incoming bits from another computer into the original format. 010010100111000111010011100101001000111101 ...

25. Network protocols Examples: • Ethernet • TCP/IP protocol suite • IP • TCP • UDP • ARP

26. Network Technologies LANs MANs WANs

27. Local-area networks (LANs) Some common LAN technologies are: • Ethernet • Token Ring • FDDI

28. Wide-area networks (WANs) Some common WAN technologies are: • Modems (Asynchronous) • Integrated Services Digital Network (ISDN) • Digital Subscriber Line (DSL) • Frame Relay • US (T) and Europe (E) – T1, E1, T3, E3 • Synchronous Optical Network (SONET)

29. Metropolitan-area networks (MANs) • A MAN is a network that spans a metropolitan area such as a city or suburban area. • A MAN usually consists of two or more LANs in a common geographic area. • For example, a bank with multiple branches may utilize a MAN.

30. Importance of bandwidth • Bandwidth - The amount of information that can flow through a network connection in a given period of time. • Available at http://www.thinkgeek.com

31. Analogies

32. Measurement • 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. • Later – The size of a bit!

33. Limitations • Bandwidth varies depending upon: • Type of media • Type of technology and protocol (LAN, WAN, wireless, etc.) • The physics of the media account for some of the difference.

34. Throughput • Throughput - The amount of data transferred from one place to another or processed in a specified amount of time. (wikopedia.com) • Often far less than the maximum possible digital bandwidth of the medium that is being used. Internetworking devices The following are some of the factors that determine throughput: • Type of data being transferred • Network topology • Number of users on the network • User computer • Server computer • Power conditions

35. Digital versus Analog Digital Signals • A signal whose state consists of discrete elements such as high or low, on or off Analog Signals • A signal which is “analogous” to sound waves • telephone lines are designed to carry analog signals

36. Digital and Analog Bandwidth Bandwidth = The width or carrying capacity of a communications circuit. Digital bandwidth = the number of bits per second (bps) the circuit can carry • used in digital communications • measure in bps Analog bandwidth = the range of frequencies the circuit can carry • used in analog communications such as voice (telephones) • measured in Hertz (Hz), cycles per second • voice-grade telephone lines have a 3,100 Hz bandwidth

37. Sound Waves

38. OSI Model • It breaks network communication into smaller, more manageable parts. • It standardizes network components to allow multiple vendor development and support. • It allows different types of network hardware and software to communicate with each other. • It prevents changes in one layer from affecting other layers. • It divides network communication into smaller parts to make learning it easier to understand.

39. ISO and the OSI Model • The International Organization for Standardization(ISO) released the OSI reference model in 1984, was the descriptive scheme they created. • “ISO. A network of national standards institutes from 140 countries working in partnership with international organizations, governments, industry, business and consumer representatives. A bridge between public and private sectors.” www.iso.ch

40. ISO and the OSI Model • “According to ISO, "ISO" is not an abbreviation. It is a word, derived from the Greek isos, meaning "equal", which is the root for the prefix "iso-" that occurs in a host of terms, such as "isometric" (of equal measure or dimensions) and "isonomy" (equality of laws, or of people before the law). • The name ISO is used around the world to denote the organization, thus avoiding the assortment of abbreviations that would result from the translation of "International Organization for Standardization" into the different national languages of members. • Whatever the country, the short form of the organization's name is always ISO.” www.whatis.com

41. OSI Model • OSI (Open Systems Interface) was released as a suite of protocols to be used as the Internet standard. • However, TCP/IP became the de facto standard. • The OSI reference model is the primary model for network communications. • Although there are other models in existence, most network vendors, today, relate their products to the OSI reference model, especially when they want to educate users on the use of their products.

42. OSI Model • The OSI reference model allows you to • view the network functions that occur at each layer • a framework that you can use to understand how information travels throughout a network. • understand, visualize, and troubleshoot the sending and receiving data on a network • visualize how information, or data packets, travels from application programs, through a network medium (e.g. wires, etc.), to another application program that is located in another computer on a network, even if the sender and receiver have different types of network media • Note: The Application Layer of the OSI model refers to networking applications, and not user applications. The use of this model can be confusing and will become clearer later!

43. OSI layers

44. OSI layers Usually not referred to. Usually not referred to.

45. OSI Layer 1 – Physical Layer • The physical layer defines the electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating the physical link between end systems. • Signals, network media (cables, wireless, …), layer 1 devices • Layer 1 devices include: • Repeaters • Hubs

46. Repeaters • Signals can only travel so far through media before they weaken, and become garbled. • This weakening of signals is called attenuation. • Attenuation increases when: • Media distances are lengthened • Nodes are added to the media

47. The Repeater • Repeaters are Layer 1 internetwork devices used to combat attenuation. • Repeaters take in weakened signals, clean them up, regenerate them, and send them on their way along the network.

48. 100 M 100 M NODE A REPEATER NODE B Repeaters Extend Distances 100 M By using repeaters, the distance over which a network can operate is extended. Example: 10Base-T (a wiring standard) is allowed to run 100 meters. One repeater can double this distance to 200 meters! NODE A NODE B

49. Repeater: Layer 1 Device Signal come in … signal go out. (after I amplify it) • Repeaters are Layer 1 devices. • They do NOT look at Layer 2, Data Link (MAC, Ethernet) addresses or Layer 3, IP Addresses.

50. Hub • Hub is nothing but a multiport repeater. • Hubs are Layer 1 devices. • Data that comes in one port is sent out all other ports, except for the port it came in on. Hubs are sometimes called • Ethernet concentrators • multiport repeaters • In Token Ring nets, Multi-station Access Units (MAU or MSAU)