Network Topology and Design

1. Network Topology and Design

2. Objectives Discuss the different physical topologies Determine which type of network media to use given a set of requirements Understand horizontal cabling standards and wiring closets Consider performance requirements and improvements for given situations Install a telecommunications connector

3. Objectives Wire a patch panel Test network cable Describe various network architecture models Discuss LAN design Describe the function that network management tools perform on a network

4. Physical Topologies:Bus A bus topology connects all stations in a linear fashion

5. Physical Topologies:Bus Bus topology advantages: It is inexpensive It is easy to design and implement because the stations are simply daisy-chained together Bus topology disadvantages: It is difficult to troubleshoot It requires termination

6. Physical Topologies:Star The star network configuration is the most popular physical topology In a star configuration, all computers or stations are wired directly to a central location: Concentrator (a.k.a. hub) Multistation Access Unit (MAU) A data signal from any station goes directly to this central device, which transmits the signal according to the established network access method for the type of network

7. Physical Topologies:Star

8. Physical Topologies:Star Star topology advantages: A break in one cable does not affect all other stations as it does in bus technologies Problems are easier to locate because symptoms often point to one station The second-easiest topology to design and install Does not require manual termination Instead the media is terminated in the station at the transceiver on the NIC and in the hub or MAU

9. Physical Topologies:Star Star topology disadvantages: Hubs, which are required for a star topology, are more expensive than bus connectors A failure at the hub can affect the entire configuration and all connected stations Uses more cable than bus topologies

10. Physical Topologies:Star Bus and star topologies can be combined to form a star/bus or bus/star physical topology Hubs that have connectors for coaxial cable as well as for twisted-pair wiring are used to form these types of networks When different physical topologies are applied to a network, the result is often called a mixed media network

11. Physical Topologies:Ring Physical rings Most often seen in Fiber Distributed Data Interface (FDDI) networks FDDI is a WAN technology Stations on a ring are wired to one another in a circle around the entire network

12. Physical Topologies:Ring Ring topology advantages: It prevents network collisions because of the media access method or architecture required Each station functions as a repeater, so the topology does not require additional network hardware, such as hubs

13. Physical Topologies:Ring Ring topology disadvantages: As in a bus network, a failure at one point can bring down the network Because all stations are wired together, to add a station the network must be shut down temporarily Maintenance on a ring is more difficult than on a star topology because an adjustment or reconfiguration affects the entire ring

14. Influence of the 5-4-3 Rule on Topologies 5-4-3 rule states that between stations on a LAN, there can be no more than five network segments connected, maximum number of repeaters is four, and maximum number of segments with stations on them is three

15. Influence of the 5-4-3 Rule on Topologies

16. Twisted-Pair Cabling Common traits of all twisted-pair cabling types and categories: The wires are copper The wires come in pairs The pairs of wires are twisted around each other The pairs of wires are usually enclosed in a cable sheath individually and as a group of wires

17. Twisted-Pair Cabling Crosstalk Signal bleed from one cable to another Usually occurs in poorly wired media Cancellation Insulates the signal from the effects of signal bleeding

18. Unshielded Twisted-Pair (UTP) Cabling used for a variety of electronic communications

19. Unshielded Twisted-Pair (UTP) UTP advantages: Thin flexible cable that is easy to string between walls Most modern buildings come with CAT 5 UTP already wired into the wall outlets or at least run between the floors Because UTP is small, it does not quickly fill up wiring ducts Costs less per foot than other type of LAN cable

20. Unshielded Twisted-Pair (UTP) UTP disadvantages: More susceptible to interference than most other types of cabling Pair twisting does help, but it does not make the cable impervious to electrical noise Its unrepeated length limit is 100 meters

21. RJ-45 Connectors Registered Jacks (RJ) Type of telecommunication connector used for twisted-pair cabling Typically RJ-45 connectors resemble the typical RJ-11 connectors that connect the phone to the wall Difference between RJ-45 connectors and RJ-11 connectors is that the former has eight wires (four-pair) and the latter four (two-pair) Some RJ-11 connectors are used with three-pair (six-wire) UTP

22. Shielded Twisted-Pair (STP) Cabling often seen in Token Ring networks Similar to UTP in that the wire pairs are twisted around each other inside the cable The advantage of STP over UTP is that it has greater protection from interference and crosstalk due to the shielding

23. Shielded Twisted-Pair (STP) STP disadvantages as compared to UTP include: A higher cost per foot The shield must be grounded at one end Improper grounding can cause serious interference Heavier and less flexible Because of its thickness, STP may not fit down narrow cable ducts

24. Coaxial Cabling Consists of either: A solid inner core (often made of copper) Wire strand conductor surrounded by insulation The two most commonly used coaxial cable: Thicknet Thinnet

25. Coaxial Cabling Advantages of coaxial cabling on a LAN include: The segment lengths are longer than UTP or STP Coaxial cable has greater interference immunity than UTP Hubs between stations are not required

26. Coaxial Cabling Disadvantages of coaxial cable: Not as easy to install as UTP More expensive than UTP Supports a maximum bandwidth of only 10 Mbps Requires more room in wiring ducts than UTP Is relatively difficult to troubleshoot thinnet and thicknet networks

27. Coaxial Cabling

28. Thinnet and Thicknet Connectors The most common connectors for RG-58 cabling on thinnet networks are: Barrel connectors T-connectors Terminators BNC Hardware connector for coaxial cable with a cylindrical shell with two small knobs allowing it to be locked into place when twisted

29. Thinnet and Thicknet Connectors Attachment unit interface (AUI) port A 15-pin physical connector interface between a computer�s network NIC and an Ethernet networking that uses 10Base5 coaxial cable

30. Fiber-Optic Cable Carries light pulses rather than electrical signals long its fibers Made of glass or plastic fibers, rather than copper wire like most other network cabling Core of the cable is usually pure glass Surrounding the glass is a layer of cladding made of glass or plastic, which traps the light in the core

31. Fiber-Optic Cable Fiber-optic cabling advantages: Can transmit over long distances Not susceptible to electromagnetic interference or crosstalk Supports extremely high transmission rates Cable has a smaller diameter and can be used in narrow wiring ducts Not susceptible to eavesdropping

32. Fiber-Optic Cable Fiber-optic cabling disadvantages: More expensive than other types of networking media More difficult and more expensive to install than any other network media Because it is fragile, it must be installed carefully and protected after installation

33. Signal Degradation Degradation sources can be internal or external When signals degrade over distance, attenuation results Three internal factors can cause attenuation: Resistance Inductive reactance Capacitive reactance

34. Signal Degradation When the internal opposition forces are combined and measured, the measure is called impedance External forces affecting network signals include: Electromagnetic interference (EMI) Radio frequency interference (RFI) Both types of interference can degrade and corrupt network signals as they travel through a wire

35. Ways to Reduce EMI/RFI on Network Cabling Keep network media away from sources of EMI Ensure that network media is installed properly Use shielded cabling Use repeaters Ensure that you install high-quality cabling

36. Horizontal Cabling Standards Horizontal cabling The twisted-pair or fiber-optic media connecting workstations and wiring closets Electronics Industries Alliance and Telecommunications Industry Association (EIA/TIA) Defines a set of specifications, EIA/TIA-568, which covers outlets near the workstation, mechanical terminations in wiring closets, and all cable running along the horizontal path between wiring closet and workstation

37. Horizontal Cabling Standards

38. Horizontal Cabling Standards EIA/TIA-568B Specifies that the maximum distance for a UTP horizontal cable run is 90 meters (295 feet) Also, patch cords (a.k.a. patch cables) located at any cross-section cannot exceed six meters (20 feet) In addition to UTP, the following cable types may be used for horizontal pathways: STP � two pairs of 150-ohm cabling Fiber-optic � a two-fiber 62.5/125 multimode cable

39. Wiring Closets Contain the wiring and wiring equipment for connecting network devices, such as routers, bridges, switches, patch panels, and hubs EIA/TIA-568 and EIA/TIA-569 standards apply to the physical layout of media and wiring closets, with the latter stating there must be a minimum of one wiring closet per floor Furthermore, when a given floor area (catchment area) exceeds 1,000 square meters, or the horizontal cabling more than 90 meters, additional wiring closets are needed

40. Wiring Closets The main distribution facility (MDF) is the central junction point for wiring of a star topology The additional closets are called intermediate distribution facilities (IDFs) IDFs are required when: Catchment area of MDF is not large enough to capture all nodes The LAN is in a multistory facility The LAN encompasses multiple buildings

41. Proximity to the POP Ensure that main wiring closet is close to the point of presence (POP) to the Internet

42. Proximity to the POP

43. Backbone Backbone cable (sometimes called vertical cabling) connects wiring closets to each other in an extended star topology EIA/TIA-568 specifies four different options for backbone cabling: 100-ohm UTP 150-ohm STP 62.5/125-micron optical fiber Single-mode optical fiber

44. Performance Considerations:Connection Speeds The real capacity of a network is sometimes referred to as throughput Factors affecting throughput include: Type of network devices being used on the network Number of nodes Power issues Network architecture Other variables

45. Performance Considerations:Utilization Potential causes of high utilization: Video or audio streaming/teleconferencing Client/server applications Host/terminal applications Routing protocols Routine maintenance tasks Broadcast traffic Ethernet collisions

46. Performance Considerations:Utilization Solutions for reducing network utilization include: Segmenting a network with connectivity Reducing number of services provided on the segment Reducing number of protocols in use on the segment Disabling bandwidth-intensive applications or protocols Relocating systems consuming the most bandwidth on the segment

47. Performance Considerations:Calculating Bandwidth and Throughput When considering an organization�s bandwidth requirements, discover types of bandwidth-intensive communications conducted on its network Transmission time Time it takes a file to transfer from one location to another

48. Performance Considerations:Collisions and Contention All stations on an Ethernet segment must share the available connection with each other This means the stations contend with one another for the opportunity to transmit on the wire When considering upgrading an existing network, check the rate of collisions on the network using a protocol analyzer or other network performance-monitoring tool

49. Performance Considerations:Resource Placement

50. Installing Telecommunication Connectors

51. Installing Telecommunication Connectors

52. Installing Telecommunication Connectors

53. Installing Telecommunication Connectors EIA/TIA-568A Wiring method used to indicate which colors are assigned to which pin for UTP cable Punch tool Used to punch down cable at the patch panel or RJ-45 wall jack

54. Patch Panel

55. Patch Panel

56. Cable Testers:Wire Map Important measurement a cable tester makes to check wiring sequence

57. Cable Testers:Wire Map

58. Cable Testers:Attenuation Attenuation is the loss of signal power over the distance of a cable Signal injector Puts traffic on a wire so that a cable tester can measure attenuation and crosstalk The lower the attenuation, the better

59. Cable Testers:Noise Alternating current (AC) signal noises are called oscillations and can alter the digital signals that computers receive on the wire The motherboard and other internal integrated circuits of a computer use the chassis as their ground Faulty AC wiring can also cause problems with transmissions because the signal reference ground is the computer chassis and grounding plate A transformer steps voltage up or down where the hot lead originates and the neutral wire is grounded

60. Cable Testers:NEXT Near end crosstalk (NEXT) Measure of interference from other wire pairs Causes of NEXT include: Split pairs Too much wire untwisted at the patch panel, jack, or connectors Bends, kinks, or stretches in the cabling

61. Cable Testers:NEXT

62. Cable Testers:Distance Measure EIA/TIA-568A specifies maximum cable lengths for network media Cables that are too long can cause delays in transmission and network errors Time-domain reflectometer (TDR) Cable tester that can detect the overall length of a cable or the distance to a cable break

63. Cable Testers:Baseline Take baseline measurements to tell how well the network is performing at a given moment Baseline measurements can include: Error rates Collision rates Network utilization

64. Network Architecture Logical topology Describes the way a signal travels in a network, which is a function of the access method Usually a bus or a ring IEEE 802 Covers issues concerning all types of networks LAN, MAN, WAN, and wireless

65. Logical Link Control (IEEE 802.2) In the IEEE 802.2 specification, the Data Link layer is divided into: The Media Access Control (MAC) sublayer The Logical Link Control (LLC) sublayer LLC sublayer is closer to software components of the protocol stack because it controls data link communications and defines Service Access Points (SAP) MAC sublayer is closer to the underlying hardware architecture

66. Logical Link Control (IEEE 802.2)

67. CSMA/CD (802.3) IEEE 802.3 defines the access method used by most Ethernet networks Jam signal 32-bit message to all computers on an Ethernet network that tells all stations not to transmit 10BaseT Describes an Ethernet network connected by twisted-pair cable that can support transmissions of 10 Mbps using baseband (digital) signals

68. CSMA/CD (802.3) 10Base2 Also known as thin Ethernet 10Base5 Also known as thick Ethernet Fast Ethernet Also known as 100BaseT Gigabit Ethernet A more recent addition to the IEEE 802.3 specifications

69. Token Ring (802.5) In the 802.5 specification, Token Ring networks use token-passing to keep track of which node is communicating Star-ring Network architecture utilizing physical star topology with logical ring topology Nearest active upstream neighbor (NAUN) Nearest active downstream neighbor (NADN)

70. Token Ring (802.5) Active monitor Computer in a Token Ring network that is powered on first and that manages the beaconing process Beaconing Fault-detection method implemented in Token Ring networks

71. Wireless Technologies (802.11) The 802.11 standard for wireless LANs specifies parameters at both Physical and Data Link layers of OSI model At the Physical layer, infrared (IR) or spread spectrum technologies are supported At the Data Link layer, 802.11 specifies Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) as the network access method

72. FDDI Fiber Distributed Data Interface (FDDI) standard Responsibility of the American National Standards Institute (ANSI) Describes a network that can span up to 100 kilometers (62 miles) over single-mode fiber-optic cabling Based on the Token Ring (802.5) specification but with different limitations

73. LAN Design Models You can choose many different network design models to implement on your network There are two basic designs strategies that are typically followed: Mesh design Hierarchical design

74. LAN Design Models

75. LAN Design Models Compared to a mesh design, a hierarchical design: Is easier to manage Is easier to troubleshoot Has improved scalability Allows easier analysis

76. Three-Layer Network Model Divides a network into three connectivity layers Consists of: Core layer Distribution layer Access layer

77. Three-Layer Network Model

78. Two-Layer Network ModelOne-Layer Network Model Two-layer network model Divides a network into two connectivity layers: Core Access One-layer network model Includes WAN connectivity equipment and organizes a network so that is can be easily adapted to the two-layer and three-layer design models in the future

79. Two-Layer Network Model

80. One-Layer Network Model

81. Network-Management Tools The most common network-management tools are: Cable testers Network monitors Network analyzers

82. Network-Management Tools

83. Network-Management Tools Other sophisticated network-management tools can be used for daily network-management and control functions These tools typically have three components: Agent Manager Administration system

84. Simple Network Management Protocol (SNMP) A Management Information Base (MIB) is a database that maintains statistics and information the SNMP reports and uses

85. Simple Network Management Protocol (SNMP) Management tasks include: Network traffic monitoring Automatic disconnection of problem nodes Connection or disconnection of nodes based on time and/or date Port isolation for testing purposes Remote management capabilities

86. CMIP Common Management Information Protocol Similar to SNMP in that it uses the MIB to monitor the network Not as widely implemented as SNMP More efficient than SNMP because the client reports the information to the management device

87. Chapter Summary There are three basic physical LAN topologies These topologies typically involve cable The IEEE has defined many standards that have influenced the way networks are designed and implemented One of the largest contributions from the IEEE is the 802 standard

88. Chapter Summary Installing media on a network is multifaceted project Obstructions and EMI/RFI must be overcome When implementing a network, you can choose on of three hierarchical models Network administrators use network monitors and network analyzers to manage a network on daily basis