Unit 1: Introduction to LANs Network Design, Case Analysis

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Unit 1 Introduction to LANsNetwork Design, Case
Analysis

• Syllabus, Course Goals and Overview
• Systems Approach to LAN Design
• Review of LAN Material
• Cabling, Media, Cable Design and Management

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Objective for Class

• Opportunity for students to gain some practical
  experience in the subject area
• Opportunity to play with various platforms,
  hands-on with servers and internetworking
  devices.
• Practical perspective
• Case Study
• Lab Exercises

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Labs

• Using the LAN Lab
• There are several classes using the labs. Please
  dont use a machine unless you are doing a lab.
• Many of the lab activities can be done from ANY
  DePaul lab or from home.
• There is a part of a lab exercise that can only
  be completed in the LAN Lab. It involves
  connecting networking devices and router
  configurations. This part will not be counted
  towards your grade as it may not be practical for
  some DL students to make it to the Lab. However,
  all students are strongly recommended to complete
  the Lab if possible for the experience.

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Systems Approach to Networking

• Goldmans Top-Down Model
• Functional Model
• Thomas Network Planning Approach

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Top-Down Model

• Start with Business level objectives
• Understand the Applications (their uses,
  requirements, quirks)
• Examine the Data (data traffic analysis -- What,
  How Much)
• Network Requirements, planning and implementation
  (logical what)
• Technology (physical how)

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Cisco Model

• Three prong approach for small to medium networks
• Three basic problems
• Media
• Protocol
• Transport

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Cisco Business Characterization

• Gather Administrative Data
• Business Goals, Corporate Structure, Geographical
  Structure, Staffing, Policies and Politics
• Gather Technical Data
• Identify applications, Analyze information flows,
  determine shared data, determine network traffic
  and access, determine network performance
  characteristics

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2. Functional Model

• A Functional Model
• Function
• Performance
• Security
• Availability/Reliability
• Cost

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Thomas Network Planning

• Murphys Law Every project takes longer than
  expected!
• Technology alone may lead to
• More profitable business
• More misery!
• Examples
• Internet connection
• E-mail access
• Planning ? Necessary Evil!

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The Planning Process

• Needs Analysis
• Site Analysis
• Equipment Matching
• Configuration Plan
• Server Directory Structure
• Configuration Lists
• Installation schedule
• System Log

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Needs Analysis

• Organizational issues that a network can address
• Need for data centralization
• Need for automation
• Need for communication
• Need for security
• Translate needs into business goals

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Site Analysis

• Drawing of a site plan
• As simple as a floor plan
• Electrical outlets
• Cable drops for voice, data, video
• Location of networkable devices
• City, State and Federal codes for electrical
  infrastructure, fire, emergency, etc.
• Inventory of existing equipment
• Be frugal!

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Equipment Matching Configuration Plan

• Try to make do with the existing equipment
• A good information source
• Solicit vendor recommendations

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Server Directory Structure

• A set of named logical addresses and objects on
  the planned network
• NOS
• Applications
• User directories
• Shared resources
• Printers, plotters, DBs, etc.
• Internet connections, servers, services, etc.

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Problem

• You have a small Auto Body shop
• Currently they have 3 computers, 2 for preparing
  estimates (with separate databases) and 1 for
  operations (bookkeeping, correspondence, etc.)
• They want to be able to access the estimating
  software from any machine but protecting the
  accounting information is very important
• What do you recommend?

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Networks and Standalone Computers

• Network
• A group of computers and other devices connected
  by some type of transmission media
• Networks enable users to share devices and data,
  collectively called a networks resources
• Standalone Computer
• Uses programs and data only from its local disks
  and is not connected to a network.

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What is a LAN?

• Key Elements
• High Communications Speed
• Very Low Error Rate
• Limited Geographic Boundaries
• Simple Cabling System
• Provides resource sharing (files, printers,
  disks, applications, etc.)
• Originally designed to use broadcast transmission
  to deliver data (that is, each transmitted data
  packet is delivered to all other devices on LAN).

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What is a LAN?

• Workstations (PCs, etc.)
• Network Interface Card (NIC) or Network Adapter
  Card provides LAN interface.
• Interconnecting Cable
• Typically twisted copper wire or optical fiber.
• Network Operating System (NOS) Software

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Network Interface Card

• Network Interface Card (NIC)
• Device that enables a workstation to connect to
  the network

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LAN Hardware

• Cabling and NIC card specs dictated by underlying
  LAN transport system (called logical topology in
  some texts)
• Ethernet
• Token Ring
• ARCNet
• Fiber Distributed Data Interface (FDDI)
• etc.

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Network Interface Card Sales 2002
Source Instat
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Network Operating Systems

• Popular NOSes
• Novell NetWare
• Microsoft Windows Networking
• UNIX / Linux
• NOS determines workstation role
• Client - can request services
• Server - can provide services

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NOS Types

• Peer-to-Peer NOS
• Every workstation has both client and server
  capabilities in NOS.
• Any user can share files with others.
• Examples Windows 95, 98, ME, NT/2000
  Workstation, Linux or UNIX systems
• Server-Based or Client/Server NOS
• File server runs server software only.
• LAN Clients run NOS client software only.
• Only file server can share files.
• Examples Novell NetWare server, Windows NT/2000
  Server, Unix/Linux

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Peer-to-Peer Communication

• Networking model with no servers all computers
  can share local resources

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Client/Server Architecture

• Networking model in which clients use a central
  file server to share applications

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Advantages of Server-Based over Peer-to-Peer
Networks

• User login accounts and passwords can be assigned
  in one place
• Access to multiple shared resources can be
  centrally granted
• Optimized to handle heavy processing loads and
  dedicated to handling requests from clients
• Can connect more than a handful of computers

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Windows 2000/2003

• Windows positives
• wide-spread acceptance and support
• familiar Windows interface
• works well with Microsoft applications
• Windows negatives
• Stability (Win2000/2003 still crashes more often
  than NetWare, Linux or UNIX)
• AD administration can be somewhat difficult
• high resource requirements

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NetWare

• NetWare positives
• Best administration for very large organizations
• Relatively small kernel
• Fastest/most efficient file / print server
• NetWare negatives
• Cost
• Training
• Decline in market share and expertise

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Linux

• Linux positives
• Stability
• Cost
• code size
• Most efficient web server
• Linux negatives
• number of applications
• support issues

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UNIX

• Various companies support their own proprietary
  versions of UNIX
• SunOS from Sun
• HP-UX from Hewlett Packard
• UIX from IBM
• Etc.
• Proprietary UNIX positives
• Very stable and scalable operating systems
• Good support available
• Proprietary UNIX negatives
• number of applications
• expense

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NetWare / Linux Alliance

• In August, 2003, Novell announced it had acquired
  Ximian, a leading developer of Linux desktop and
  management software.
• Early 2004, Novell acquired SuSe Linux, a Linux
  developer.
• Nov 2004, Novell announced its Novell Linux
  Desktop 9 suite.
• Of course, they will continue to support the old
  NetWare operating system as well

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Server O.S. Shipments(in millions)
Source IDC
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NOS Marketplace

• UNIX is installed on more servers than any other
  operating system.
• Novell NetWare was the top selling LAN operating
  system between 1986 and 1997.
• Win NT/2000/2003 and Linux are now outselling
  NetWare.
• NetWare still has the greatest installed base for
  LAN servers.

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Elements Common to All NOS

• Topology
• Physical layout of a computer network

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Elements Common to All NOS

• Protocol
• Rules the network uses to transfer data
• Data Packets
• The distinct units of data transmitted from one
  computer on a network to another
• Addressing
• Scheme for assigning a unique identifying number
  to every workstation on a network
• The number that uniquely identifies each
  workstation or device on a network is its address

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Elements Common to All NOS

• Transmission Media
• Means through which data is transmitted and
  received

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How Networks Are Used

• Services
• Features provided by a network
• File and Print Services
• Communications Services
• Mail Services
• Internet Services
• Management Services

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LAN File Servers

• A File Server provides shared files and
  directories that may be accessed by Client
  machines.
• All services provided through messages
• Client sends Request message to Server
• Server performs action and sends Response message
  to Client
• Note that message sizes are limited (max. 1500
  bytes of data in any Ethernet message, for
  example), so in some cases one Request may result
  in multiple Response messages.

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File Servers

• Clients send requests Open File, Close File,
  Read File, Write File, etc.
• File Server receives request, performs action,
  sends response.

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Example Get File
Open File
File Opened
Read Data
Data
Close File
File Closed
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Client / Server Compatibility

• In order for a Client machine and a Server to be
  able to talk to each other, they must both
  implement the same File Services Protocol.
• A File Services Protocol defines a particular set
  of request and response messages a server
  understands
• Novell Netware servers use NetWare Core Protocol
  (NCP).
• Microsoft servers use Server Message Blocks (SMB)
  protocol.
• UNIX servers often use Network File System (NFS)
  protocol.

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File Server Access

• File Servers (and other servers) are accessible
  from the Windows desktop using
• My Network Places (Windows 2000, XP)
• Network Neighborhood (Windows 95, 98, ME, NT)
• File Manager (Windows 3.1 / Windows for
  Workgroups)

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LAN Share Identifiers

• Shared objects on LAN Servers are commonly
  identified with the following notation
• \\ltservergt\ltobjectgt
• Example I want to access a shared directory
  called MEMOS on a server named DPU_FACULTY_5, I
  go to
• \\DPU_FACULTY_5\MEMOS
• Example I want to access a printer named
  STUD_PRINT through a server named DPU_STUDENTS, I
  go to
• \\DPU_STUDENTS\STUD_PRINT

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Network Drives

• For DOS/Windows, unused drive letters can be
  mapped to directory on Server.
• These Network Drives can be used identically to
  local drives (like A), but cause file actions to
  be done on Server.

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Security

• Users must log on (with user name password) to
  a server before accessing shared resources.
• Network Manager controls access rights for each
  user to each resource.

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File Access Permissions

• Administrator can allow/disallow for any user
• See any server
• View names of shared directories on any server
• View any file name(s)
• Read contents of file(s)
• Execute file(s)
• Modify file(s)
• Delete files
• Change file names
• Set access permissions for other users

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Other Services

• Print Service (via file/print services protocol)
• Provide shared access to printer.
• Database Service (i.e. SQL protocol)
• Structured query access to shared database files.
• Remote Access Service (i.e. RAS protocol)
• Shared access to modems for connectivity in/out
  of LAN.

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Other Services

• Directory/Name Service (i.e. DNS protocol)
• Keeps track of names and relationships among all
  LAN users, devices and services
• IP Address Service (i.e. DHCP protocol)
• Assign IP addresses and routing information to
  LAN workstations.
• Network Management Service (i.e. SNMP protocol)
• Gather performance and configuration information
  from other LAN workstations and servers

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Other Services

• Gateway Services (various protocols)
• Access and Protocol translation to another
  computing environment (ex IBM mainframe)
• FAX Services (via file/print protocol)
• Access to shared FAX machine/services.
• Application Services (i.e. WTS or Citrix
  protocols)
• Allows clients to run some application programs
  on the server rather than locally.

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Other Services

• Web/Intranet Services (HTTP protocol)
• Receive and process HTTP web commands
• E-Commerce Services (via HTTP (and other)
  protocols)
• Provide Web-based transaction services with high
  performance, reliability and security required.
• GroupWare Services
• Provide office services based on common
  e-mail/groupware platform.

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Problem

• You are designing a network for an office
  complex. Several buildings must be linked
  together with high-performance long-distance
  links, and servers within the building must be
  linked together with a high-speed backbone.
  Hundreds of client computers in each building
  must be linked together inexpensively. What
  media will you use?

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Network Cabling

• Coaxial Cable
• Widely used in 1980s, but not today
• Expensive, difficult to manage
• Twisted Copper Pair
• Least expensive
• Limited distance (typically 100 meters or 330
  feet)
• Susceptible to electromagnetic noise
• Fiber Optic Cable
• Most expensive
• Longest distance
• Highest bandwidth

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Media Characteristics

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Media Cost Factors

• Cost of physical cable
• Cost of installation
• Cost of new infrastructure versus reusing
  existing infrastructure
• Cost of maintenance and support
• Cost of a lower transmission rate affecting
  productivity
• Cost of obsolescence

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Network Cabling

• Baseband and Broadband Transmission
• In baseband transmission, digital signals are
  sent through direct current (DC) pulses applied
  to the wire
• In broadband transmission, signals are modulated
  as radio frequency (RF) analog pulses that use
  different frequency ranges

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Network Cabling

• Coaxial Cable
• Central copper core surrounded by an insulator
• Braiding insulates coaxial cable
• Sheath is the outer cover of a cable
• Foundation for Ethernet network in the 1980s

Coaxial cable
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Network Cabling
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Network Cabling

• Thicknet (10Base5)
• Thicknet
• Also called thickwire Ethernet
• Rigid coaxial cable used for original Ethernet
  networks
• IEEE designates Thicknet as 10Base5 Ethernet

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Network Cabling

• Thicknet (10Base5)
• Throughput
• Cost
• Connector
• Noise immunity
• Size and scalability

Thicknet cable transceiver with detail of a
vampire tap piercing the core
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Network Cabling

• Thinnet (10Base2)
• Also known as thin Ethernet, was most popular
  medium for Ethernet LANs in the 1980s
• Throughput
• Cost
• Size and scalability
• Connector
• Noise Immunity

Thinnet BNC connectors
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Network Cabling

• Signal Bounce
• Caused by improper termination
• Travels endlessly between two ends of network
• Prevents new signals from getting through

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Network Cabling

• Twisted-Pair (TP) Cable
• Similar to telephone wiring
• Consists of color-coded pairs of insulated copper
  wires twisted around each other and encased in
  plastic coating
• Twists help reduce effects of crosstalk,
  interference caused by signals traveling on
  nearby wire pairs infringing on another pairs
  signals
• Alien Crosstalk occurs when signals from adjacent
  cables interfere with another cables transmission

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Network Cabling

• Twist Ratio
• Number of twists per meter or foot in a
  twisted-pair cable

Twisted-pair cable
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Network Cabling

• Shielded Twisted-Pair (STP)
• Twisted wire pairs are individually insulated and
  surrounded by shielding

STP cable
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Network Cabling

• Unshielded Twisted-Pair
• Consists of one or more insulated wire pairs
  encased in a plastic sheath
• Does not contain additional shielding

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Network Cabling

• To manage network cabling, its necessary to be
  familiar with standards used on modern networks,
  particularly Category 3 (CAT3) and Category 5
  (CAT5)

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RJ-45 Connector
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Fiber Optic Cable

• Fiber-Optic Cable
• Contains one or several glass fibers at its core
• Cladding is the glass shield around the core

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Fiber Optic Cable

• Single-Mode Fiber
• Carries single path of light to transmit data
• More expensive, higher data rates (to 10 Gbps and
  beyond)
• Multimode Fiber
• Carries many paths of light over a single or many
  fibers
• Less expensive, but lower data rates due to
  timing differences between different paths (up to
  1 Gbps)

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Network Cabling

• Fiber-Optic Cable
• High Throughput
• High Cost
• Connector
• Good Noise immunity
• Size and scalability
• Wavelength-Division Multiplexing (WDM)
• Allows multiple light data signals to be sent
  over single fiber

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Cable System Design

• Horizontal Cabling
• Connects data jacks (RJ-45, typically) in walls
  of building back to a telecom wiring closet
• May be one or more wiring closets per floor of
  building
• Typically twisted pair cable is used
• Vertical Cabling
• Interconnects the wiring closets (between
  multiple floors of the building)
• Forms the network backbone
• Typically optical fiber cable is used, but may
  also be twisted pair cable.

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Horizontal Wiring
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Vertical Wiring
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Cable Design and Management

• Structured Cabling
• Method for uniform, enterprise-wide, multivendor
  cabling systems
• Specified by TIA/EIA 568/569 Commercial Building
  Wiring Standard

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Cable Design and Management

• Horizontal wiring
• No more than 90 meters of twisted pair between
  data jack and patch panel in wiring closet

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Cable Design and Management

• Work area
• Patch cable is a relatively short section of
  twisted-pair cabling with connectors on both ends
  that connect network devices to data outlets

Standard TIA/EIA wall jack
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Cable Design and Management

• Entrance facilities
• Backbone wiring (Vertical Wiring)
• Backbone is essentially a network of networks
• Risers provide vertical connections between floors

TIA/EIA specifications for backbone cabling
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Cable Design and Management

• Equipment room
• Telecommunications closet
• Punch-down block is a panel of data connectors to
  allow interconnections on a wire-by-wire basis
• Patch panel is a panel of data receptors (RJ-45)
  that allow interconnections on a cable-by-cable
  basis

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Structured cabling hierarchy
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Installing Cable
Typical UTP cabling installation
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RJ-45 Pin-out for Ethernet
Pin numbers and color codes for an RJ-45 connector
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Installing Cable

• Do not untwist twisted-pair cables more than
  one-half inch before inserting them
• Do not strip off more than 1 inch of insulation
  from copper wire in twisted-pair cables
• Watch bend radius limitations for cable being
  installed
• Bend radius is maximum arc into which a cable can
  be looped before its data transmission is
  impaired
• Test each segment of cabling with cable tester
• Use only cable ties to cinch groups of cable
  together

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Installing Cable

• Avoid laying cable across floor where it may
  sustain damage
• Install cable at least 3 feet away from
  fluorescent lights or other sources of EMI
• Always leave slack in cable runs
• If running cable in the plenum, the area above
  ceiling tile or below subflooring, make sure
  cable sheath is plenum-rated
• Pay attention to grounding requirements

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Atmospheric Transmission Media

• Infrared Transmission
• Infrared networks use infrared light signals to
  transmit data
• Direct infrared transmission depends on
  transmitter and receiver remaining within line of
  sight
• In indirect infrared transmission, signals can
  bounce off of walls, ceilings, and any other
  objects in their path
• Infrared can easily provide throughputs of 10
  Mbps

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Atmospheric Transmission Media

• RF Transmission
• Radio frequency (RF) transmission relies on
  signals broadcast over specific frequencies
• Narrowband concentrates significant RF energy at
  a single frequency
• Spread spectrum uses lower-level signals
  distributed over several frequencies
  simultaneously

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Wireless LAN Configurations
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IEEE 802.11 LANs

• The most frequently used wireless LANs today use
  the IEEE 802.11 standards
• IEEE 802.11b provides up to 11 Mbps for 250-300
  foot range
• IEEE 802.11a new equipment can provide up to 54
  Mbps within 90 foot range
• IEEE 802.11g available as of June 2003 -
  extends 802.11b up to 22 Mbps.
• Note that these are all shared bandwidth LANs and
  include protocol overhead, so individual user
  throughputs can be much lower (5.5 Mbps was best
  case in one test).

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IEEE 802.11 LANs

• 802.11 Design
• 802.11 Access Points (AP) are fixed transceivers
  (connected into wired infrastructure) that can
  communicate with mobile clients within a range of
  30-50 meters.
• 802.11 Network Cards placed into workstations or
  laptops allows them to communicate with nearest
  AP.

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LAN Topologies

• How are Workstations connected together?
• Bus Topology
• Ring Topology
• Star Topology ltltlt Most popular today
• Ad-hoc Topology (wireless)

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Bus Topology

• Used in early LANs (1970s, 1980s)
• All workstations and servers connected to same
  physical cable.
• Each transmission was broadcast to all other
  devices on LAN.
• Problems
• One cable problem downs whole network
• Hard to locate problems when they occur

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Bus Topology Example10Base5 Ethernet
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Simple LAN Topologies

• Terminators stop signals after they have reached
  their destination to prevent signal bounce
• Signal bounce
• Phenomenon in which signals travel endlessly
  between the two ends of a bus network

Terminated bus network
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Simple LAN Topologies

• Ring topology
• Each node is connected to the two nearest nodes
  so the entire network forms a circle
• Active topology
• Each workstation transmits data
• Each workstation functions as a repeater

Typical ring network
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Ring Topology

• Devices connect sequentially in a ring.
• Each device transmits to the next.
• Problems
• One cable problem downs the network
• One workstation problem downs the network
• Used today only with dual-ring systems that can
  survive cable cuts

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Dual Ring ExampleFiber Distributed Data
Interface (FDDI)
Self healed after Link Failure
Self-healing
FDDI dual-
link failure
attached
adapters
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Star Topology

• All workstations and servers connect into a hub
  or concentrator
• Hub typically acts as multiport repeater - it
  re-transmits each bit received to all other
  attached devices
• Advantages
• Hub can isolate any problems that occur
• Intelligent (managed) hub can collect network
  performance statistics

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Star Topology Example10BaseT Ethernet
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Ad-Hoc Topology

• In 802.11 wireless LANs, stations may be anywhere
  as long as they are within range of the closest
  Access Point.
• In some designs, no AP is necessary (direct
  PC-to-PC communications)
• In some designs, stations can move between Access
  Points without breaking the connection.

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Hybrid LAN Topologies

• Hybrid topology
• Combines one physical topology with the
  operations of another topology
• Star-wired ring (Token Ring)
• Uses physical layout of a star in conjunction
  with token ring-passing data transmission method

Star-wired ring topology network
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Hybrid LAN Topologies

• Star-wired bus (Ethernet)
• In a star-wired bus topology, groups of
  workstations are star-connected to hubs, but data
  is broadcast as on a bus

Star-wired bus network topology
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Hybrid LAN Topologies

• Daisy-Chained (Token Ring)
• Daisy chain is linked series of devices

Daisy-chained star-wired bus topology
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Hybrid LAN Topologies

• Hierarchical (All LANs)
• Uses layers to separate devices by their priority
  or function

Hierarchical ring topology
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Enterprise-Wide Topologies

• Backbone Network
• Determines how to connect together wiring closets
  throughout a building or enterprise.
• Backbone network designs
• Serial backbone
• Distributed backbone
• Collapsed backbone
• Parallel backbone

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Enterprise-wide Topologies
Distributed backbone connecting multiple LANs
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Enterprise-wide Topologies

• Collapsed backbone
• Uses a router or switch as the single central
  connection point for multiple subnetworks

Collapsed backbone network
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Enterprise-wide Topologies

• Parallel Backbone
• This variation on collapsed backbone arrangement
  consists of more than one connection from the
  central router or switch to each network segment

Parallel backbone network
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Enterprise-wide Topologies

• Mesh networks
• Routers are interconnected with other routers
  with at least two pathways connecting each router

Example of a mesh network