CIS 81 Fundamentals of Networking Chapter 4: Network Access

1. CIS 81 Fundamentals of NetworkingChapter 4: Network Access Rick Graziani Cabrillo College graziani@cabrillo.edu Spring 2018

2. Chapter 4 • 4.1 Physical Layer Protocols • 4.2 Network Media • 4.3 Data Link Layer Protocols • 4.4 Media Access Control • 4.5 Summary

3. Comparing the two models • At the network access layer, the TCP/IP protocol suite does not specify which protocols to use when transmitting over a physical medium. • Only describes the handoff from the internet layer to the physical network protocols. • OSI Layers 1 and 2 discuss the necessary procedures to access the media and the physical means to send data over a network.

4. Focus on Data Link Layer IP IP Data Link Layer: Post-It Label on IP “box” (demo) Physical Layer: Roll or toss tennis balls (demo)

5. Reminder of encapsulation/decapsulation Data Link Trailer Data Link Header IP Header TCP Header HTTP Header Data Data Link Trailer Data Link Trailer Data Link Header Data Link Header IP Packet IP Packet Data Link Trailer Data Link Trailer Data Link Header Data Link Header IP Packet IP Packet Data Link Trailer Data Link Trailer Data Link Header Data Link Header IP Packet IP Packet Data Link Trailer Data Link Header IP Header TCP Header HTTP Header Data

6. Getting it ConnectedConnecting to the Network • A physical connection can be a wired connection using a cable or a wireless connection using radio waves.

7. Getting it ConnectedConnecting to the Network • Switches and wireless access points are often two separate dedicated devices, connected to a router. • Many homes use integrated service routers (ISRs),

8. Getting it ConnectedNetwork Interface Cards • Network Interface Cards (NICs) connect a device to the network. • Ethernet NICs are used for a wired connection whereas WLAN (Wireless Local Area Network) NICs are used for wireless.

9. Getting it ConnectedNetwork Interface Cards Connecting to the Wireless LAN with a Range Extender • Wireless devices must share access to the airwaves connecting to the wireless access point. • Slower network performance may occur • A wired device does not need to share its access • Each wired device has a separate communications channel over its own Ethernet cable.

10. The Physical Layer • The OSI physical layer provides the means to transport the bits that make up a data link layer frame across the network media.

11. Purpose of the Physical LayerPhysical Layer Media • The physical layer produces the representation and groupings of bits for each type of media as: • Copper cable: The signals are patterns of electrical pulses. • Fiber-optic cable: The signals are patterns of light. • Wireless: The signals are patterns of microwave transmissions.

12. Purpose of the Physical LayerPhysical Layer Standards • Upper OSI layers are performed in software designed by software engineers and computer scientists. • TCP/IP suite are defined by the Internet Engineering Task Force (IETF) in RFCs

13. Purpose of the Physical LayerPhysical Layer Standards • Who maintaining physical layer standards? • Different international and national organizations, regulatory government organizations, and private companies

14. Fundamental Principles of Layer 1Physical Layer Fundamental Principles

15. Fundamental Principles of Layer 1Physical Layer Fundamental Principles • Encoding or line encoding - Method of converting a stream of data bits into a predefined "codes”. • Signaling - The physical layer must generate the electrical, optical, or wireless signals that represent the "1" and "0" on the media.

16. Fundamental Principles of Layer 1Encoding and Signaling • http://www.flukenetworks.com/content/neal-allens-network-maintenance-and-troubleshooting-guide-revealed

17. Fundamental Principles of Layer 1Bandwidth • Bandwidth is the capacity of a medium to carry data. • Typically measured in kilobits per second (kb/s) or megabits per second (Mb/s).

18. Fundamental Principles of Layer 1Throughput • Throughput is the measure of the transfer of bits across the media over a given period of time. • Due to a number of factors, throughput usually does not match the specified bandwidth in physical layer implementations. • http://www.speedtest.net/ • http://ipv6-test.com/speedtest/

19. Fundamental Principles of Layer 1Types of Physical Media • Different types of interfaces and ports available on a 1941 router

20. Network MediaCopper Cabling

21. Copper CablingCharacteristics of Copper Media 2 1 4 3 • Signal attenuation - the longer the signal travels, the more it deteriorates - susceptible to interference • Crosstalk - a disturbance caused by the electric or magnetic fields of a signal on one wire to the signal in an adjacent wire.

22. Copper CablingCopper Media • Counter the negative effects of different types of interference some cables are wrapped in metallic shielding • Counter the negative effects of crosstalk, some cables have opposing circuit wire pairs twisted together which effectively cancels the crosstalk.

23. Copper CablingUnshielded Twisted-Pair (UTP) Cable • Read this section… good stuff!

24. Copper CablingShielded Twisted-Pair (STP) Cable Braided or Foil Shield Foil Shields

25. Copper CablingCoaxial Cable

26. Copper CablingCooper Media Safety

27. UTP CablingProperties of UTP Cabling • Read this section… more good stuff!

28. UTP CablingUTP Cabling Standards

29. UTP CablingUTP Connectors

30. UTP CablingTypes of UTP Cable

31. UTP CablingTesting UTP Cables

32. Fiber Optic CablingProperties of Fiber Optic Cabling

33. Fiber Optic CablingProperties of Fiber Optic Cabling

34. Fiber Optic CablingFiber Media Cable Design • Please read this section…. More good stuff!

35. Fiber Optic CablingTypes of Fiber Media

36. Fiber Optic CablingNetwork Fiber Connectors

37. Fiber Optic CablingTesting Fiber Cables

38. Fiber Optic CablingFiber versus Copper

39. Wireless MediaProperties of Wireless Media

40. Wireless MediaTypes of Wireless Media

41. Wireless Media802.11 Wi-Fi Standards

42. The Data Link Layer • The OSI physical layer provides the means to transport the bits that make up a data link layer frame across the network media.

43. Purpose of the Data Link LayerThe Data Link Layer • The data link layer is responsible for the exchange of frames between nodes over a physical network media.

44. Purpose of the Data Link LayerData Link Sublayers 802.3 Ethernet 802.11 Wi-Fi 802.15 Bluetooth • Data Link layer has two sublayers (sometimes): • Logical Link Control (LLC) – Software processes that provide services to the Network layer protocols. • Frame information that identifies the Network layer protocol. • Multiple Layer 3 protocols, (ICMP, IPv4 and IPv6) can use the same network interface and media. • Media Access Control (MAC) - Media access processes performed by the hardware. • Provides Data Link layer addressing and framing of the dataaccording to the protocol in use.

45. Purpose of the Data Link LayerProviding Access to Media • At each hop along the path, a router: • Accepts a frame from a medium • De-encapsulates the frame • Re-encapsulates the packet into a new frame • Forwards the new frame appropriate to the medium of that segment of the physical network

46. Data Link LayerLayer 2 Frame Structure • The data link layer prepares a packet for transport across the local media by encapsulating it with a header and a trailer to create a frame.

47. TopologiesControlling Access to the Media

48. Media Access Control • Media Access Control - Regulates the placement of data frames onto the media. • The method of media access control used depends on: • Media sharing • Do more than two nodes share the media? • If so, how? (Switches, hubs, etc.)

49. Serial vs multi-access Multi-access Point-to-Point • Point-to-Point networks • Only two nodes • /30 subnets are common (later) • Protocols: PPP, HDLC, Frame Relay • Multi-access networks (LANs) • Multiple nodes • Subnets mask range depends upon the number of hosts (nodes) • Protocols: Ethernet, 802.11 (wireless), Frame Relay Multipoint

50. TopologiesPhysical and Logical Topologies