MIS 430 Part III

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MIS 430 Part III

• Local Area Networks

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Background

• 95 of LANs are Ethernet
• Traditional (802.3)
• Switched
• Wireless (802.11 etc)

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Use LANs for

• Information Sharing
• Data Files, Email, Web pages
• Resource Sharing
• Printers, access to specialty hardware
• Access to software applications
• We use Keyserver to meter software to users
• Beware illegal activities SPA software police
• http//www.spa.org/piracy/default.asp SW
  Publishers Association
• Gateway to other networks

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Types of LAN

• Dedicated Server
• File, Web, Email, Database, Print servers
• Remote access server (RAS) for ISP
• Sophisticated Network SW
• Peer to peer server
• Regular client PC serves files and printers
• Internet Connection Sharing (ICS)
• Limit to

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Day in the Life LAN Admin

• Arrive before others check network
• Run routine diagnostics
• Check daily logs
• Do daily backup (incremental is short)
• Check for Windows critical security updates,
  anti-virus updates
• Respond to user emails about problems
• Plan for future upgrades, SW rollouts, security
  improvements

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I. Basic LAN Components

• NIC-network interface card
• Network cables
• Network hub (switch or router)
• Network operating system (client, server
  versions)
• Client computers
• Server (can be a client)

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Network Interface Card (NIC)

• Built into motherboard or as an add in card
• PCI bus versus ISA bus (expansion slot)
• PC Card plugs into laptop PC Card slot on side
  and sticks out (remove when putting in the case)
• miniPCI card fits inside a laptop (wireless)
• Speed 10 vs 10/100 vs 100 Mbps
• Connector RJ-45 vs BNC or AUI
• Plug and Play computer configures NIC vs.
  program via SW vs. set jumper switches
• Boot PROM allows booting from server

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Network Cables

• Most use UTP unshielded twisted pair
• Also have coax (BNC) and fiber optic
• See Tech Focus 6-1 p. 192 for cables
• Cat 5 and 5e 100 Mbps twisted pair
• Cat 6 250 up to 1000 Mbps (1 gigabit)
• RG-58 coax 802.2 (RG-59 is TV cable)
• RG-8 coax 802.5 (more expensive than RG-58)
• X3T9.5 fiber optic (FDDI)
• Price/foot in table add cost of connectors
• Cat 5 wire 123 6 (Bl, Bl/Wh, Or, Or/Wh)

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Cable Management, p. 193

• Terry College of Bus, U of Georgia
• No cable plan a mess!
• Nobody knew where the cables and hubs were had
  to crawl around ceiling wires
• Found asbestos in ceiling! Had to fix it
• Univ spent 400K to install Cat 5 to every
  office installed fiber-optic BN between network
  segments

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Network Hub Fig 6.2 p. 193

• Hub repeats signal to other nodes
• Dumb hub only repeats
• Smart hub managed (SNMP) and program
• Switching Hub switches signal only to
  destination (aka switch)
• Measure of ports
• Hub speed 10, 10/100, or 100 Mbps
• Router often combines switched hub

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Network Operating System

• NOS controls the network
• One set runs on server (Novell Netware Windows
  Server NT, 2000, 2003 Unix)
• One set runs on client (Windows 9x, ME, 2000, XP,
  Mac, etc.)
• NOS (server) replaces regular server operating
  system
• Provides file sharing, print sharing, web
  service, FTP service, email service, etc.
• Windows 2003 looks remarkably like Windows XP

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Network Profiles

• Gives the resources that are shared on the
  network
• User profile for each person shows what resources
  can be accessed

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II. Ethernet (IEEE 802.3)

• Traditional (shared) Ethernet
• Topology layout of network
• Logical versus physical topology
• Bus
• Star most prevalent
• Loop or ring
• Hybrid

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Ethernet Media Access Control

• Contention CSMA/CD carrier sense multiple
  access with collision detection
• So long as nobody is broadcasting on network, a
  node can transmit
• If two packets collide, jamming occurs and the
  two parties wait a random time and redo

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Types of Ethernet

• See figure 6-5 p. 199
• 10Base-2 (1010 Mbps, Basebaseband, and 2 is
  coaxial cable
• 10Base-T 10 Mbps twisted pair
• 100Base-T 100 Mbps UTP
• 1000Base-T 1 Gbps Ethernet
• 40GbE 40 Gbps fiber
• Some use 10/100 which switches to match speed

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III. Switched Ethernet

• Switch replaces hub only transmits packet to
  desired node, not all nodes
• Greatly enhances the capacity of cable because
  switch buffers packets, allowing transmissions on
  all lines simultaneously
• Helpful as users increases
• 10/100 switch allows mixture of 10 and 100 Mbps
• Switch uses forwarding table (like routing table)
  which builds dynamically
• This is a layer-2 switch (at data link layer)

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Switching Modes

• For first few minutes, works like a hub until it
  identifies where clients connect
• Cut through switching
• Sends pack immediately before checking CRC
• Store and forward switching
• Process packet normally after CRC
• Fragment-free switching
• Send after reading 1st 64 bytes

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V. Best Practice LAN Design

• Effective Data Rates depend on ..
• Nominal data rate in physical layer
• Error rate ( of retransmissions)
• Efficiency of data link layer protocols used
• Efficiency of media access control methods
• CSMA/CD work well in low-volume subnets (the
  elbow curve fig 6.7 p. 205)
• Thus keep utilization
• Switched ethernet works better than hub
• See Fig 6.8 p. 207 for effective data rates/user

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Recommendations

• Costs drop after new technology appears 10BaseT
  and 100BaseT are now cheap!
• Very small networks 10BaseT
• Switched 10BaseT over Cat 5e cable is fine unless
  high volume data (streaming) is done
• Hi vol switched 100BaseT on Cat 5e or fiber
  optic cables

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VI. Improve Network Performance

• Software
• Basically fine tune network settings in NOS disk
  cache, buffer space, etc.
• Add a new protocol that is faster
• Hardware
• Buy another (or faster) server
• Increase memory in server
• RAID drive or higher performance disk
• NIC get server version NIC with high performance

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Improve Network Performance

• Improve circuit capacity
• Upgrade to 100 Mbps hub
• Upgrade to switched hub
• Split into 2 or more subnets and add a server NIC
  for each network segment
• Move high demand clients to different segments

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Improve Network Performance

• Reduce network demand
• Move files to client computers (e.g., heavily
  used applications)
• Use disk cache SW on clients to reduce need to
  access files on servers
• Adjust time when users work busiest times are 9
  AM and right after lunch FlexTime is very
  popular in IT