1. Cabling and Topology
Chapter 3

2. Objectives
• Explain the different types of network
topologies
• Describe the different types of network
cabling
• Describe the IEEE networking standards

3. Overview

4. Three Parts to Chapter 3
• Network Topology
• Most common standardized cable types
• IEEE Committees for network technology
standards

5. Topology

6. • Network topology
– The way that cables and other pieces of
hardware connect to one another

7. Bus and Ring
• Bus topology
– Single bus cable
– Connects all computer in a line
• Ring topology
– Central ring of cable
– Connects all computers in a ring

8. Figure 3.1 Bus and ring topologies

9. Figure 3.2 Real-world bus topology

10. • Data flow
– Bus topology
• Data flows from each computer onto the bus
• Termination required at ends to prevent data reflection
– Ring Topology
• Data flows from one computer to next one in circle
• No end of cable and no need for termination

11. Figure 3.3 Terminated bus topology

12. Figure 3.4 Ring topology moving in a certain direction

13. • Problem with Bus and Ring
– Entire network stops working if the cable is
broken at any point.

14. Figure 3.5 Nobody is talking!

15. Star
• Star topology has a central connection for all
computers
• Fault tolerance – benefit over bus and ring
• Was not successful early on
– More expensive than bus and ring
– Difficult to redesign early bus and ring hardware

16. Figure 3.6 Star topology

17. Hybrids
• Hybrid topology combines topologies
– Physical topology
• How cables physically look
– Signaling topology
• How the signals travel electronically

18. • Star-ring topology
– Physical star + signaling ring
– Ring shrunk down into a hub-like box
– Cables connect to the hub
• Star-bus topology
– Physical star + signaling bus
– Segment (bus) shrunk down into a hub-like
box
– Cables connect to the hub

19. Figure 3.7 Shrinking the ring

20. Figure 3.8 Shrinking the segment

21. Mesh and Point-to-Multipoint
• Mesh topology
– Every computer connects to every other computer via
two or more routes
• Two types of mesh topology
– Partially-meshed topology
• At least two machines have redundant connections
– Fully-meshed topology
• Every computer connects directly to every other
computer
• Most fault tolerant

22. Figure 3.9 Mesh and point-to-multipoint

23. Figure 3.10 Partially- and fully-meshed topologies

24. • Point-to-multipoint topology
– A single system is a common source
Figure 3.11 Comparing star and point-to-multipoint

25. Point-to-Point
• Two computers connect directly
• No need for a central hub
• Wired or wireless
Figure 3.12 Point-to-Point

26. Parameters of a Topology
• Topology is only one feature of a network
• Other network features
– What is the cable made of?
– How long can it be?
– How do machines decide which machine should
send data and when?

27. • Network technology
– A practical application of a topology, and other
technologies that comprise a network
– Examples
• 10BaseT
• 1000BaseF
• 10GBaseLX

28. Cabling

29. Coaxial Cable
• A central conductor wire
• Surrounded by an insulating material
• Surrounded by a braided metal shield
Figure 3.13 Cutaway view of coaxial cable

30. • Outer mesh layer of coaxial cable
– Shields transmissions from electromagnetic
interference (EMI)
Figure 3.14 Coaxial cable showing braided metal shielding

31. • Coaxial connectors in older networks
– Bayonet-style BNC Connectors
– Vampire taps pierced the cable
Figure 3.15 BNC connector on coaxial cable

32. • Connecting cable modems
– F-type screw-on connector
Figure 3.16 F-type connector on coaxial cable

33. • RG rating for coaxial cable
– Developed by military
– RG-6 is predominate cable today
– RG-59 cable is rarely used
Figure 3.17 RG-6 cable

34. • Coaxial cable Ohm rating
– Relative measure of resistance
– RG-6 and RG-59 are rated at 75 Ohms
Figure 3.18 Ohm rating (on an older RG-58 cable used
for networking)

35. • Splitting coaxial cable
Figure 3.19 Coaxial splitter

36. • Extending coaxial cable
Figure 3.20 Barrel connector

37. Twisted Pair
• Most common network cabling
• Twisted pairs of cables, bundled together
• Twists reduce crosstalk interference

38. Shielded Twisted Pair (STP)
• Shielding protects from electromagnetic
interference (EMI)
• Needed in locations with excessive EMI
• Most common is IBM Type 1 cable
Figure 3.21 Shielded twisted pair

39. Unshielded Twisted Pair (UTP)
• Most common
• Twisted pairs of wires with plastic jacket
• Cheaper than STP
• Also used in telephone systems
Figure 3.22 Unshielded twisted pair

40. CAT Ratings
• Category (CAT) ratings are grades of cable
ratings
• Rated in MHz
• Most common categories are in Table 3.1

41. Table 3.1 CAT Ratings for UTP
CAT Max
Rating Frequency Max Bandwidth Status with TIA/EIA
CAT1 <1 MHz Analog phone lines only No longer recognized
CAT2 4 MHz 4 Mbps No longer recognized
CAT3 16 MHz 16 Mbps Recognized
CAT4 20 MHz 20 Mbps No longer recognized
CAT5 100 MHz 100 Mbps No Longer recognized
CAT5e 100 MHz 1000 Mbps Recognized
CAT 6 250 MHz 10000 Mbps Recognized

42. UTP Bandwidth
• Bandwidth is the maximum amount of data
that will go through a cable per second
• 100 MHz originally translated to 100 Mbps
• With bandwidth-efficient encoding
– CAT 5e at 100 MHz = 1,000 Mbps max bandwidth
– CAT 6 at 250 MHz = 10,000 Mbps

43. Using the Correct Cable
• Look on the box
CAT level
Figure 3.23 CAT level marked on box of UTP

44. Using the Correct Cable
• Look on the cable CAT level
Figure 3.24 CAT level on UTP

45. Register jack (RJ) connectors
• RJ-11 (two pairs of wires) for telephones
• RJ-45 (four pairs of wires) for networks
Figure 3.25 RJ-11 (top) and RJ-45 (bottom)
connectors

46. Fiber-Optic
• Fiber-optic cable transmits light
• Not affected by EMI
• Excellent for long-distance transmissions
– Single copper cable works up to a few hundred
meters
– Single fiber-optic cable works up to tens of
kilometers

47. Composition of Fiber-Optic
• Core: the glass fiber
• Cladding: reflects signal down the fiber
• Buffer: gives strength
• Insulating jacket: protects inner components
Figure 3.26 Cross section of fiber-optic cabling

48. Standardization of Fiber-Optic
• Two-number designator
– Core and cladding measurements
– 62.5/125 μm

49. Often used in cable pairs
• One for sending
• One for receiving
• Cable may be connected together like a lamp
cord
Figure 3.27 Duplex fiber-optic cabling

50. Fiber-Optic Light Sources
• Two possible light sources
– Light Emitting Diodes (LEDs) – called multimode
• Usually 850 nm wavelength
– Lasers – called single-mode
• Prevents modal distortion (a problem with multimode)
• High transfer rates over long distances
• 1310 or 1550 nm wavelength

51. Fiber-Optic connectors
• ST: bayonet-style
• SC: push-in
• LC: duplex

52. Figure 3.28 From left to right: ST, SC, and LC
fiber-optic connectors

53. Other Cables
• Classic Serial
– RS-232 recommended standard (RS)
• Dates from 1969
• Has not changed significantly in 40 years
• Usually 850 nm wavelength
– Most common serial port is 9-pin, male
D-subminiature connector
– Slow data rates: about 56,000 bps
– Only point-to-point connections

54. Serial port
Figure 3.29 Serial port

55. • Parallel
– Up to 2 Mbps
– Limited to point-to-point
– IEEE 1284 committee sets standards
Figure 3.30 Parallel connector

56. • FireWire
– IEEE 1394 standard
– Limited to point-to-point
– Very fast – up to 800 Mbps
– Unique connector

57. Figure 3.31 FireWire connector

58. Cable Fire Ratings
• Underwriters Laboratories and the National
Electrical Code (NEC)
– Polyvinyl chloride (PVC) rating has no
significant fire protection
• Lots of smoke and fumes
– Plenum-rated cable
• Less smoke and fumes
• Costs three to five times as much as PVC-rated cable
– Riser-rated cable for vertical runs

59. Networking Industry
Standards – IEEE

60. • Institute of Electrical and Electronics
Engineers (IEEE) defines standards
– 802 Working Group began in February of 1980
• Defines frames, speed, distances, and types of cabling
for networks
• IEEE 1284 committee sets standards for parallel
communications

61. Figure 3.32 Parallel cable marked IEEE 1284–compliant

62. Table 3.2 IEEE 802 Subcommittees
IEEE 802 LAN/MAN Overview & Architecture
IEEE 802.1 Higher Layer LAN Protocols
802.1s Multiple Spanning Trees
802.1w Rapid Reconfiguration of Spanning Tree
802.1x Port Based Network Access Control
IEEE 802.2 Logical Link Control (LLC); now inactive
IEEE 802.3 Ethernet
802.3ae 10 Gigabit Ethernet
IEEE 802.5 Token Ring;; now inactive
IEEE 802.11 Wireless LAN (WLAN); specifications, such as Wi-Fi
IEEE 802.15 Wireless Personal Area Network (WPAN)
IEEE 802.16 Broadband Wireless Access (BWA); specification for implementing Wireless
Metropolitan Area Network (Wireless MAN); referred to also as
WiMax
IEEE 802.17 Resilient Packet Ring (RPR)
IEEE 802.18 Radio Regulatory Technical Advisory Group
IEEE 802.19 Coexistence Technical Advisory Group
IEEE 802.20 Mobile Broadband Wireless Access (MBWA)
IEEE 802.21 Media Independent Handover
IEEE 802.22 Wireless Regional Area Networks