CIS 1140 Network Fundamentals

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CIS 1140 Network Fundamentals

• Chapter 5 Topologies and Ethernet Standards

Collected and Compiled By JD Willard MCSE, MCSA,
Network, Microsoft IT Academy
Administrator Computer Information Systems
Instructor Albany Technical College
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Attention Accessing Demos

• This course presents many demos.
• The Demos require that you be logged in to the
  Virtual Technical College web site when you click
  on them to run.
• To access and log in to the Virtual Technical
  College web site
• To access the site type www.vtc.com in the url
  window
• Log in using the username CIS 1140 or
  ATCStudent1
• Enter the password student (case sensitive)
• If you should click on the demo link and you get
  an Access Denied it is because you have not
  logged in to vtc.com or you need to log out and
  log back in.
• If you should click on the demo link and you are
  taken to the VTC.com web site page you should do
  a search in the search box for the CompTIA
  Network (2009 Objectives) Course and run the
  video from within that page.

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Objectives

• Describe the basic and hybrid LAN physical
  topologies, and their uses, advantages, and
  disadvantages
• Describe the backbone structures that form the
  foundation for most networks
• Compare the different types of switching used in
  data transmission
• Explain how nodes on Ethernet networks share a
  communications channel
• Identify the characteristics of several Ethernet
  standards

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Network Topologies

• Topology is the term used to describe how devices
  are connected and how messages flow from device
  to device
• There are two types of network topologies
• Physical topology is the physical layout of the
  network, including cable and device configuration
• Logical topology refers to the method used to
  communicate between the devices
• It is important to understand the physical
  topology before designing networks, because they
  can affect the logical topology chosen, how the
  building is cabled, and what kind of media is used

Network Topology Basics Demo
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Simple Physical Topologies

• Physical topology
• Physical layout of nodes on a network
• Depicts broad scope
• Does not specify
• Device types
• Connectivity methods
• Addressing schemes
• Topology integral to type of network, cabling
  infrastructure, and transmission media used
• Fundamental shapes
• Bus, ring, star
• Hybrid

Physical Topologies Demo
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Topologies pt. 1 Demo
Topologies pt. 2 Demo
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Bus

• Bus topology
• Single cable
• The single cable is called the bus and supports
  one channel, where each node shares total
  capacity
• Connects all network nodes
• No intervening connectivity devices
• One shared communication channel
• Physical medium
• Coaxial cable
• Passive topology
• Node listens for, accepts data
• Uses broadcast to send

Bus Topology Demo
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Basic Ethernet Bus

• An Ethernet network where all machines are daisy
  chained using coaxial cable (Thin
  Ethernet/Thin-net or Thick Ethernet/Thick-net).
• Machine 2 wants to send a message to machine 4.
• First it 'listens' to make sure no one else is
  using the network.
• If it is all clear it starts to transmit its data
  on to the network (represented by the yellow
  flashing screens).
• Each packet of data contains the destination
  address, the senders address, and of course the
  data to be transmitted.
• The signal moves down the cable and is received
  by every machine on the network but because it is
  only addressed to number 4, the other machines
  ignore it.
• Machine 4 then sends a message back to number 2
  acknowledging receipt of the data (represented by
  the purple flashing screens).

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• Terminators
• Bus requires a terminator at each end of cable
• 50-ohm resistors
• Stop signal at end of wire
• Prevents signal bounce
• Signal bounce
• Signal travels endlessly between two network ends
• One end grounded
• Removes static electricity

A terminated bus topology network
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Bus (contd.)

• Bus topology advantage
• Easy to install and add devices
• Relatively inexpensive
• Requires less cable
• Disadvantages
• Requires 50 ohm terminators at each end of the
  cable
• Requires grounding loop
• Does not scale well
• Difficult to troubleshoot
• Not very fault tolerant
• Entire network shuts down if the cable breaks
  (signal bounce)

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Ring

• Ring topology
• Node connects to nearest two nodes
• Circular network
• Clockwise data transmission
• One direction (unidirectional) around ring
• Token passing
• Token Ring and FDDI networks
• Active topology
• Workstation participates in data delivery
• Data stops at destination
• Physical medium
• Twisted pair or fiber-optic cabling

Ring Topology Demo
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Ring (contd.)

• Ring advantages
• No network collisions
• Drawbacks
• Malfunctioning workstation can disable network
• Not very flexible or scalable

A ring topology network
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Star

• Star topology
• Node connects through central device
• Hub, Router or switch
• Physical medium
• Twisted pair or fiber-optic cabling
• Single cable connects only two devices

Star Topology Demo
A star topology network
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Star

• Most popular fundamental layout
• Modern Ethernet networks based on star topology
• 1024 addressable logical network nodes maximum

How Ethenet accesses the cable and transmits
using a hub.
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Star (contd.)

• Star advantages
• Fault tolerant
• Easier to troubleshoot
• A break in the cable does not shut down the
  network
• Higher reliability
• Flexible
• No terminators required
• Star disadvantages
• Uses more cable than ring or bus networks
• Connectivity devices more expensive than
  terminators
• Connectivity device failures take down entire LAN
  segments

Any single cable connects only two devices,
Cabling problems affect two nodes at most
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Hybrid Topologies

• Pure bus, ring, star topologies
• Rarely exist because too restrictive
• Hybrid topology
• More likely
• Complex combination of pure topologies
• Several options

Hybrid Topology Demo
Hybrid Topologies Demo
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Star-Wired Ring

• Star-wired ring topology
• Star physical topology
• Ring logical topology
• Token passing data transmission method

• Benefit
• Star fault tolerance
• Reliability of token passing
• Network use
• Token Ring networks
• IEEE 802.5

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Star-Wired Ring (contd.)

• Token Ring MAUs can be connected together using
  straight-through patch cables to connect the Ring
  Out port of one MAU and the Ring In port of the
  next MAU until the network of MAUs forms a
  circle.
• Up to 255 stations can be connected to the
  network when using Shielded Twisted Pair cable
  and 72 when using Unshielded Twisted Pair cable.

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MAU Showing Internal Ring

• A Token Ring hub (MAU) changes the topology from
  a physical ring to a star wired ring.
• MAU can automatically bypass any ports that are
  disconnected or have a cabling fault.

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Star-Wired Bus

• Star-wired bus topology
• Workstation groups
• Star-connected devices
• Networked via single bus
• Advantage
• Cover longer distances
• Easily interconnect, isolate different segments
• Drawback
• Cabling, connectivity device expense
• Basis for modern Ethernet networks

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Star-Wired Bus (contd.)
A star-wired bus topology network
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Logical Topologies

• Logical topology how data is transmitted between
  nodes
• May not match physical topology
• Bus logical topology signals travel from one
  network device to all other devices on network
• Required by bus, star, star-wired physical
  topologies
• Ring logical topology signals follow circular
  path between sender and receiver
• Required by ring, star-wired ring topologies
• Broadcast domain
• All nodes connected to single repeating device or
  switch

Logical Topologies Demo
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Logical Topology Physical Topology Description
Bus Bus Messages are sent to all devices connected to the bus.
Bus Star Messages are sent to all devices connected to the bus.
Ring Ring Messages are sent from device-to-device in a predetermined order until they reach the destination device.
Ring Star Messages are sent from device-to-device in a predetermined order until they reach the destination device.
Star Star Messages are sent directly to (and only to) the destination device.
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Backbone Networks

• Cabling connecting hubs, switches, routers
• More throughput
• Large organizations
• Fiber-optic backbone
• Cat 5 or better for hubs, switches
• Enterprise-wide network backbones
• Complex, difficult to plan
• Enterprise
• Entire organization
• Significant building block backbone

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Serial Backbone

• Simplest backbone
• Two or more devices
• Connect using single medium in daisy-chain
  fashion
• Daisy-chain
• Linked series of devices
• Benefit
• Logical growth solution
• Modular additions
• Low-cost LAN infrastructure expansion
• Easily attach switches

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Serial Backbone (contd.)

• Backbone components
• Gateways, routers, switches
• Serial connection of repeating devices
• Limited distance spanned between each

• Standards
• Define number of repeating devices allowed
• Exceed standards
• Intermittent, unpredictable data transmission
  errors
• Not used in modern networks

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Distributed Backbone

• Connectivity devices
• Connected to hierarchy of central connectivity
  devices
• Benefit
• Simple expansion, limited capital outlay
• More complicated distributed backbone
• Connects multiple LANs, LAN segments using
  routers

• Additional benefits
• Workgroup segregation
• May include daisy-chain linked repeating devices
• Consider length
• Drawback
• Potential for single failure points

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Collapsed Backbone

• Uses router or switch
• Single central connection point for multiple
  subnetworks
• Highest layer
• Single router or switch with multiprocessors
• Central router failure risk

• Routers may slow transmission
• Advantages
• Interconnect different subnetwork types
• Central management

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Parallel Backbone

• Most robust network backbone
• More than one central router, switch
• Connects to each network segment
• Requires duplicate connections between
  connectivity devices

• Advantage
• Redundant links
• Increased performance
• Better fault tolerance

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Switching

• Logical network topology component
• Determines connection creation between nodes
• Three methods
• Circuit switching
• Packet switching
• Multiprotocol label switching

Circuit Switching and Packet Switching (330)
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Circuit Switching

• Connection established between two network nodes
• Before transmitting data
• Dedicated bandwidth
• Data follows same initial path selected by switch
• Monopolizes bandwidth while connected
• Resource wasted
• Uses
• Live audio, videoconferencing
• Traditional telephone calls
• Most popular

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Packet Switching

• Breaks data into packets before transporting
• Packets
• Travel any network path to destination
• Find fastest circuit available at any instant
• Need not follow each other
• Need not arrive in sequence
• Reassembled at destination
• Requires speedy connections for live audio, video
  transmission
• Examples
• Ethernet networks
• Internet

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MPLS (Multiprotocol Label Switching)

• Introduced by IETF in 1999
• Enables multiple types of Layer 3 protocols
• To travel over any one of several Layer 2
  protocols
• Most often supports IP
• Common use
• Layer 2 WAN protocols
• Offers potentially faster transmission than
  packet- or circuit-switched networks
• Advantages
• Use packet-switched technologies over
  traditionally circuit switched networks
• Create end-to-end paths
• Addresses traditional packet switching
  limitations
• Better QoS (quality of service)

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Ethernet

• Most popular networking technology used on modern
  LANs
• Benefits
• Flexible
• Can run on various network media
• Excellent throughput
• Reasonable cost
• All variations
• Share common access method
• CSMA/CD

What is Ethernet? Demo
Ethernet Demo
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CSMA/CD (Carrier Sense Multiple Access with
Collision Detection)

• Network access method
• Controls how nodes access communications channel
• Necessary to share finite bandwidth
• Carrier sense
• Ethernet NICs listen, wait until free channel
  detected
• Multiple access
• Ethernet nodes simultaneously monitor traffic,
  access media

CSMA / CD Demo
CSMA/CD Access Method demo
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CSMA/CD (contd.)

• Collision
• Two nodes simultaneously
• Check channel, determine it is free, begin
  transmission
• Collision detection
• Manner nodes respond to collision
• Requires collision detection routine
• Enacted if node detects collision
• Jamming
• NIC issues
• 32-bit sequence
• Indicates
• previous
• message faulty

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CSMA/CD (contd.)

• Heavily trafficked network segments
• Collisions common
• Segment growth
• Performance suffers
• Critical mass number dependencies
• Data type and volume regularly transmitted
• Collisions corrupt data, truncate data frames
• Network must detect and compensate

CSMA/CD process
CSMA/CD and CSMA/CA (533)
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CSMA/CD (contd.)

• Collision domain
• Portion of network where collisions occur
• Ethernet network design
• Repeaters repeat collisions
• Result in larger collision domain
• Switches and routers
• Separate collision domains
• Collision domains differ from broadcast domains

Broadcast domains and collision domains
Collision Domains Demo
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CSMA/CD (contd.)

• Ethernet cabling distance limitations
• Effected by collision domains
• Data propagation delay
• Data travel time too long
• Cannot identify collisions accurately
• 100 or 1000 Mbps networks
• Three segment maximum connected with two
  repeating devices
• 10 Mbps buses
• Five segment maximum connected with four
  repeating devices

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Ethernet Standards for Copper Cable

• IEEE Physical layer standards
• Specify how signals transmit to media
• Differ significantly in signal encoding
• Affect maximum throughput, segment length, wiring
  requirements

Ethernet Network Types Demo
BASE Terminology Demo
Ethernet Topologies (732)
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Ethernet Standards for Copper Cable (contd.)

• 10Base-T
• 10 represents maximum throughput 10 Mbps
• Base indicates baseband transmission
• T stands for twisted pair
• Requires CAT3 or higher UTP
• Two pairs of wires transmit and receive
• Full-duplex transmission

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A 10Base-T network

• Follows 5-4-3 rule of networking
• Five network segments
• Maximum segment length is 100 meters
• Four repeating devices (hubs)
• Three populated segments maximum

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Ethernet Standards for Copper Cable (contd.)

• 100Base-T (Fast Ethernet)
• IEEE 802.3u standard
• Similarities with 10Base-T
• Baseband transmission, star topology, RJ-45
  connectors
• 100Base-TX
• 100-Mbps throughput over twisted pair
• Full-duplex transmission doubles effective
  bandwidth

Fast Ethernet Demo
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A 100Base-T network

• Supports three network segments maximum
• Connected with two repeating devices
• 100 meter segment length limit between nodes

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Ethernet Standards for Copper Cable (contd.)

• 1000Base-T (Gigabit Ethernet)
• IEEE 802.3ab standard
• 1000 represents 1000 Mbps
• Base indicates baseband transmission
• T indicates twisted pair wiring
• Four pairs of wires in Cat 5 or higher cable
• Transmit and receive signals
• Data encoding scheme different from 100Base-T
• Standards can be combined
• Maximum segment length 100 meters, one repeater

Gigabit Ethernet Demo
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Ethernet Standards for Copper Cable (contd.)

• 10GBase-T
• IEEE 802.3an
• Pushing limits of twisted pair
• Requires Cat 6, 6a, or 7 cabling
• Maximum segment length 100 meters
• Benefits
• Very fast data transmission
• Cheaper than fiber-optic
• Uses
• Connect network devices
• Connect servers, workstations to LAN

Even Faster Ethernet Demo
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Ethernet Over Copper Summary
Category Standard Bandwidth Cable Type Maximum Segment Length
Ethernet 10BaseT 10 Mbps (half duplex)20 Mbps (full duplex) Twisted pair (Cat3, 4, or 5) 100 meters
Fast Ethernet 100BaseTX 100 Mbps (half duplex)200 Mbps (full duplex) Twisted pair (Cat5 or higher) Uses 2 pairs of wires 100 meters
Gigabit Ethernet 1000BaseT 1,000 Mbps (half duplex)2,000 Mbps (full duplex) Twisted pair (Cat5 or higher) 100 meters
10 Gigabit Ethernet 10GBaseT 10 Gbps (full duplex only) Twisted pair (Cat5e, 6, or 7) 100 meters
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Ethernet Standards for Fiber-Optic Cable

• 100Base-FX (Fast Ethernet)
• 100-Mbps throughput, baseband, fiber-optic
  cabling
• Multimode fiber containing at least two strands
• Half-duplex mode
• One strand receives one strand transmits
• 412 meters segment length
• Full duplex-mode
• Both strands send and receive
• 2000 meters segment length
• One repeater maximum
• IEEE 802.3u standard

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Ethernet Standards for Fiber-Optic Cable (contd.)

• 1000Base-LX (1-Gigabit Ethernet)
• IEEE 802.3z standard
• 1000 1000-Mbps throughput
• Base baseband transmission
• LX reliance on 1300 nanometers wavelengths
• Longer reach than any other 1-gigabit technology
• Single-mode fiber 5000 meters maximum segment
• Multimode fiber 550 meters maximum segment
• One repeater between segments
• Excellent choice for long backbones

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Ethernet Standards for Fiber-Optic Cable (contd.)

• 1000Base-SX (1-Gigabit Ethernet)
• Differences from 1000Base-LX
• Multimode fiber-optic cable (installation less
  expensive)
• Uses short wavelengths (850 nanometers)
• Maximum segment length dependencies
• Fiber diameter, modal bandwidth used to transmit
  signals

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Ethernet Standards for Fiber-Optic Cable (contd.)

• 1000Base-SX (contd.)
• Modal bandwidth measurement
• Highest frequency of multimode fiber signal (over
  specific distance)
• MHz-km
• Higher modal bandwidth, multimode fiber caries
  signal reliably longer
• 50 micron fibers 550 meter maximum length
• 62.5 micron fibers 275 meter maximum length
• One repeater between segments
• Best suited for shorter network runs

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10-Gigabit Fiber-Optic Standards

• Extraordinary potential for fiber-optic cable
• Pushing limits
• 802.3ae standard
• Fiber-optic Ethernet networks
• Transmitting data at 10 Gbps
• Several variations
• Common characteristics
• Star topology, allow one repeater, full-duplex
  mode
• Differences
• Signals light wavelength maximum allowable
  segment length

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10-Gigabit Fiber-Optic Standards (contd.)

• 10GBase-SR and 10GBase-SW
• 10G 10 Gbps
• Base baseband transmission
• S short reach
• Physical layer encoding
• R works with LAN fiber connections
• W works with SONET fiber connections
• Multimode fiber 850 nanometer signal
  transmission
• Maximum segment length
• Depends on fiber diameter

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10-Gigabit Fiber-Optic Standards (contd.)

• 10GBase-LR and 10GBase-LW
• 10G 10 Gbps
• Base baseband transmission
• L long reach
• Single-mode fiber 1310 nanometer signal
  transmission
• Maximum segment length
• 10,000 meters
• 10GBase-LR WAN or MAN
• 10GBase-LW SONET WAN links

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10-Gigabit Fiber-Optic Standards (contd.)

• 10GBase-ER and 10GBase-EW
• E extended reach
• Single-mode fiber
• Transmit signals with 1550 nanometer wavelengths
• Longest fiber-optic segment reach
• 40,000 meters (25 miles)
• 10GBase-EW
• Encoding for SONET
• Best suited for WAN use

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Ethernet Over Fiber Summary
Category Standard Bandwidth Cable Type Maximum Segment Length
Fast Ethernet 100BaseFX 100 Mbps (multimode cable) Fiber optic 412 meters
Gigabit Ethernet 1000BaseSX (short) 1,000 Mbps (half duplex)2,000 Mbps (full duplex) Fiber optic 220 to 550 meters depending on cable quality
Gigabit Ethernet 1000BaseLX (long) 1,000 Mbps (half duplex)2,000 Mbps (full duplex) Fiber optic 550 meters (multimode)10 kilometers (single-mode)
10 Gigabit Ethernet 10GBaseSR/10GBaseSW 10 Gbps (full duplex only) Multimode fiber optic 300 meters
10 Gigabit Ethernet 10GBaseLR/10GBaseLW 10 Gbps (full duplex only) Single mode fiber optic 10 kilometers
10 Gigabit Ethernet 10GBaseER/10GBaseEW 10 Gbps (full duplex only) Single mode fiber optic 40 kilometers
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Multiple types of Ethernet on a WAN
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Ethernet Frames

• Four types
• Ethernet_802.2 (Raw)
• Ethernet_802.3 (Novell proprietary)
• Ethernet_II (DIX)
• Ethernet_SNAP
• Frame types differ slightly
• Coding and decoding packets
• No relation to topology, cabling characteristics
• Framing
• Independent of higher-level layers

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Using and Configuring Frames

• Ensure all devices use same, correct frame type
• Node communication
• Ethernet_II used today
• Frame type configuration
• Specified using NIC configuration software
• NIC autodetect
• Importance
• Know frame type for troubleshooting

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Frame Fields

• Common fields
• 7-byte preamble, 1-byte start-of-frame delimiter
• SFD (start-of-frame delimiter) identifies where
  data field begins
• 14-byte header
• 4-byte FCS (frame check sequence)
• Frame size range 64 to 1518 total bytes
• Larger frame sizes result in faster throughput
• Improve network performance
• Properly manage frames

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Ethernet_II (DIX)

• Developed by DEC, Intel, Xerox (abbreviated DIX)
• Before IEEE
• Most commonly used on contemporary Ethernet
  networks

Ethernet Frames Demo

• The preamble is a set of alternating ones and
  zeroes terminated by two ones (i.e., 11) that
  marks it as a frame.
• The destination address identifies the receiving
  host's MAC address.
• The source address identifies the sending host's
  MAC address.
• The 2-byte type field identifies the Network
  layer protocol
• The data, or the information that needs to be
  transmitted from one host to the other.
• Optional bits to pad the frame. Ethernet frames
  are sized between 64 and 1518 bytes. If the frame
  is smaller than 64 bytes, the sending NIC places
  "junk" data in the pad to make it the required 64
  bytes.
• The FCS/CRC (frame check sequence/cyclic
  redundancy check) is the result of a mathematical
  calculation performed on the frame. The CRC helps
  verify that the frame contents have arrived
  uncorrupted.

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PoE (Power over Ethernet)

• IEEE 802.3af standard
• Supplying electrical power over Ethernet
  connections
• Two device types
• PSE (power sourcing equipment)
• PDs (powered devices)
• Requires Cat 5 or better copper cable
• Connectivity devices must support PoE
• Compatible with current 802.3 installations

PoE capable switch
PoE adapters
Power over Ethernet (345)
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Summary

• Physical topology describes basic network
  physical layout
• Examples bus, ring, star, hybrid
• Logical topology describes signal transmission
• Network backbones
• Serial, distributed, collapsed, parallel
• Switching
• Manages packet filtering, forwarding
• Ethernet
• Cabling specifications, data frames, PoE

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The End