Chapter 4: Network Topology And Network Design

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CCNA Guide to Cisco Networking

• Chapter 4 Network Topology And Network Design

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Objectives

• Discuss the different physical topologies
• Describe various network architecture models
• Determine which types 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

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Objectives (continued)

• Install a telecommunications connector
• Wire a patch panel
• Test network cable
• Discuss LAN design
• Describe the function that network-management
  tools perform on a network

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Physical Topologies

• Bus topology
• Bus topology advantages
• Inexpensive
• Easy to design
• Easy to implement
• Bus topology disadvantages
• Difficult to troubleshoot
• Requires termination

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Physical Topologies (continued)
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Physical Topologies (continued)

• Star topology
• Star topology advantages
• Break in one cable does not affect other devices
  (except up links)
• Easy to locate problems
• Easy to install
• Does not require termination like bus topology
• Star topology disadvantages
• Center of star topology device (hub) can be
  expensive
• Hub failure can affect entire topology
• Amount of cable is expensive

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Physical Topologies (continued)
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Physical Topologies (continued)

• Ring topology
• Ring topology advantages
• Prevents network collisions
• Each station acts like a repeater
• Ring topology disadvantages
• Cable break can affect all devices
• Temporarily shut down network to add a new
  station
• Maintenance and monitoring is difficult

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Influence Of The 5-4-3 Rule On Topologies
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Influence Of The 5-4-3 Rule On Topologies
(continued)
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Network Architecture

• IEEE 802
• Logical Link Control (IEEE 802.2)
• CSMA/CD (802.3)
• Token Ring (802.5)
• Wireless Technologies (802.11)
• FDDI

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Network Architecture (continued)
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Media

• Twisted-Pair cabling have the following in common
• Copper based data transmission
• Copper wires come in pairs
• Each Wire of a pair is twisted around each other
• Copper wires are enclosed in a sheath
• All wire pairs are enclosed in a sheath

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Media (continued)

• Unshielded twisted-pair (UTP)
• Advantages of UTP cable
• Thin and flexible
• Easy to install
• Many modern buildings come with CAT 5 installed
• Small size does not fill up wiring ducts fast
• Inexpensive per foot
• Disadvantages of UTP cable
• Susceptible to interference
• Cable length is 100 meters or 328 feet
• Register Jacks (RJ)
• RJ-45

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Media (continued)
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Media (continued)

• Shielded twisted-pair (STP)
• Advantages of STP cable
• Greater protection from interference
• Thin and flexible
• Overall it is easy to install
• Disadvantages of STP cable
• Inexpensive per foot but more than UTP
• STP must be grounded, problems exists if not
  grounded properly
• More difficult to install than UTP
• Small size but does fill up wiring ducts faster
  than UTP

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Media (continued)

• Coaxial cabling (Thicknet and Thinnet)
• Advantages of coaxial cabling
• Cable lengths are longer than UTP/STP
• Less susceptible to interference than UTP
• Hubs are not required, direct connection
• Disadvantages of coaxial cabling
• Thicknet is very difficult to install
• More expensive than UTP
• Difficult to troubleshoot

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Media (continued)
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Media (continued)
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Media (continued)

• Thinnet and Thicknet Connectors
• RG-58 cabling
• BNC
• Attachment unit interface (AUI)
• Barrel connectors
• T-connectors
• Terminators

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Media (continued)
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Media (continued)

• Fiber-Optic cable
• Advantages of fiber-optic cabling
• Transmit data over long distances
• Not susceptible to EMI
• High transmission rates
• Not susceptible to eavesdropping
• Small cable size
• Disadvantages of fiber-optic cabling
• Expensive
• Cable can be easily damaged during install making
  installations more difficult
• Manual termination of ends is time consuming

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Media (continued)
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Media (continued)
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Media (continued)
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Signal Degradation

• Three internal factors of attenuation
• Resistance
• Inductive reactance
• Capacitive reactance
• All three combined are called impedance
• External signal degradation
• Electromagnetic interference (EMI)
• Radio frequency interference (RFI)

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Signal Degradation (continued)

• Reduce EMI/RFI
• Do not place copper media next to
• Fluorescent lights
• Generators/motors
• High-voltage electrical wire
• Proper installation
• Use quality cable
• Use shielded cabling
• Use repeaters to strengthen signal on long cable
  runs

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Horizontal Cabling Standards

• Twisted-pair or fiber-optic connections between
  wiring closets
• Electronic Industries Alliance and
  Telecommunications Industry Association (EIA/TIA)
• EIA/TIA-568
• UTP horizontal cable run max 90 meters
• Horizontal cross connect max 6 meters
• Workstation to horizontal drop max 3 meters

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Horizontal Cabling Standards (continued)
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Wiring Closets

• Wiring closets
• EIA/TIA-568 and EIA/TIA-569
• Catchment area
• Main distribution facility (MDF)
• Intermediate distribution facility (IDF)

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Wiring Closets (continued)

• Proximity to the POP
• Backbone
• Sometimes called vertical cabling
• EIA/TIA-568 specifies four different cables for
  backbone installations
• 100-ohm UTP
• 150-ohm STP
• 62.5/125-micron optical fiber
• Single mode optical fiber

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Wiring Closets (continued)
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Wiring Closets (continued)
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Performance Considerations

• Connection speeds
• Throughput
• Utilization
• Video or audio streaming/teleconferencing
• Client/server applications
• Host/terminal applications
• Routing protocols
• Routine maintenance tasks
• Broadcast traffic
• Ethernet collisions

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Performance Considerations (continued)

• Solutions for reducing network utilization
• Segment network with switch, bridge, or router
• Reduce the number of services provided on the
  network
• Reduce the number of protocols on the network
• Control access to bandwidth intensive
  applications or protocols

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Performance Considerations (continued)

• Calculating bandwidth and throughput
• Transmission Time file size/bandwidth
• (T Fs/Bw)
• Throughput file size/download time
• (Tp Fs/Dt)
• Collisions and contention
• Protocol analyzer
• Resource placement

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Performance Considerations (continued)
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Installing Telecommunications Connectors
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Installing Telecommunications Connectors
(continued)
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Installing Telecommunications Connectors
(continued)
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Patch Panel
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Patch Panel (continued)
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Patch Panel (continued)
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Testing Cable

• Cable testers
• Wire map
• Attenuation
• Noise
• Near end crosstalk (NEXT)
• Distance measure
• Baseline
• Error rates
• Collision rates
• Network utilization

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Testing Cable (continued)
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Testing Cable (continued)
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Testing Cable (continued)
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Testing Cable (continued)
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LAN Design Models

• Two basic design strategies
• Mesh
• Hierarchical
• Three-layer network model
• Core
• Distribution
• Access layer
• Two-layer network model
• One-layer network model

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LAN Design Models (continued)
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LAN Design Models (continued)
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LAN Design Models (continued)
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Network Management Tools

• Common tools
• Cable testers
• Network monitors
• Network analyzers
• Network monitors and network analyzers have in
  common
• Agent
• Manager
• Administration system

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Network Management Tools (continued)

• Simple Network Management Protocol (SNMP)
• Management information base (MIB)
• 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
• Common management information protocol (CMIP)

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Network Management Tools (continued)
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Network Management Tools (continued)
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Network Management Tools (continued)
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Summary

• There are three basic physical LAN topologies
  bus, star, and ring
• These topologies, or layouts, typically involve
  cable, such as UTP, STP, coaxial, or fiber
• The network architecture used on a LAN defines
  the physical topology, the media used, and the
  network access method
• The most popular architectures are 10BaseT,
  100baseTx and Token Ring
• The IEEE has defined many standards that have
  influenced the way networks are designed and
  implemented

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Summary (continued)

• It has also defined different network access
  methods, which include CSMA/CD, token-passing,
  and CSMA/CA
• One of the largest contributions from the IEEE is
  the 802 standard, which has subsets that define
  Ethernet (802.3),Token Ring (802.5), and wireless
  (802.11) network architectures
• The 802.2 standard from the IEEE subdivided the
  OSI Data Link layer into two parts to make
  functional distinctions between the Media Access
  Control (MAC) sublayer and the Logical Link
  Control (LLC) sublayer
• Ethernet is also known by its access method,
  CSMA/CD (Carrier Sense Multiple Access with
  Collision Detection)

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Summary (continued)

• Token Ring uses an entirely different access
  method that is governed by token passing
• The token, a small data frame, is passed from
  station to station around the ring, and a station
  can transmit only when it has the token
• FDDI uses token-passing like Token Ring networks,
  but it is not subject to the same limitations
• CSMA/CA is a network access method specified by
  the wireless LAN standard802.11
• This standard supports spread spectrum and
  infrared technologies for use on wireless LANs

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Summary (continued)

• CSMA/CA nodes listen before sending but determine
  when to send based on a random backoff factor
• Before transmitting, CSMA/CA nodes send a
  notification that they are going to transmit
• Installing media on a network is a multifaceted
  project
• The layout of the network should be determined
  and documented
• The number of wiring closets necessary, as well
  as their locations, must be determined

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Summary (continued)

• Standards for wiring closets, cable runs,
  distances, and cable must be considered when the
  routes are established
• Obstructions and EMI/RFI must be overcome
• After you install cable, you should test it for
  wiring, performance, and configuration problems
• Cable testers can be used to determine if cables
  are wired correctly, if they meet length
  standards, and if they have attenuation or noise
  problems
• When implementing a network, you can choose one
  of three hierarchical network models one-layer,
  two-layer, or three-layer

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Summary (continued)

• The one-layer network model is the least complex,
  and is a flat structure where all components
  function at essentially the same level
• The two-layer model separates the WAN from the
  rest of the internal network, which is usually
  done by adding routers with packet filters
• In the three-layer model, the internal LANs are
  further divided by backbone cabling, which has
  additional routers with packet filters
• In this model, the WAN connection is called the
  core layer, the backbone cabling and routers form
  the distribution layer, and the individual LANs
  function at the access layer

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Summary (continued)

• Network administrators use network monitors and
  network analyzers to manage a network on a daily
  basis
• These tools can also be used to troubleshoot
  abnormal situations
• The main difference between a network monitor and
  network analyzer is the level of service provided
• The network analyzer typically offers more
  advanced features, such as SNMP querying, remote
  administration, and even automatic problem
  correction