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
• 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.
• Remember that passwords are case sensitive so
  enter it in all lower case letters.

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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 LANs
• Understand the transmission methods underlying
  Ethernet networks
• Compare the different types of switching used in
  data transmission

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Network Topologies

• 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
• Physical topologies are classified according to
  three geometric shapes bus, ring and star

Types of Topologies Demo
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Simple Physical Topologies

• Physical topology physical layout of nodes on a
  network
• May create hybrid topologies
• Does not specify
• Device types
• Connectivity methods
• Addressing schemes
• Topology integral to type of network, cabling
  infrastructure, and transmission media used
• Three fundamental shapes
• Bus
• Ring
• Star

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

• Bus consists of a single cable that connects all
  the nodes of a network without intervening
  connectivity devices, and requires a terminator
  at each end
• The single cable is called the bus and supports
  one channel, where each node shares total
  capacity
• Bus advantages easy to install and add devices
  requires less cable less expensive
• Bus disadvantages requires 50 ohm terminators at
  each end of the cable entire network shuts down
  if the cable breaks difficult to troubleshoot
  requires grounding loop
• Terminators stop signals after reaching end of
  wire
• Prevent signal bounce
• Inexpensive, not very scalable
• Difficult to troubleshoot, not fault-tolerant

The 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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Bus (continued)
A terminated bus topology network
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Ring

• Ring is where each node is connected to the two
  nearest nodes, effectively forming a circle
• Data is transmitted in one direction around the
  ring, and is typically done so using token
  passing
• The ring is used by Token Ring and FDDI networks
• Ring advantages no network collisions each node
  functions as a repeater less cable required
• Ring disadvantages Single malfunctioning node
  can disable entire network not flexible or
  scalable modifications requires network shutdown

The Ring Topology Demo
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Ring
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Star

• Star is where each node is connected through a
  central device, such as a hub
• All nodes transmit data to the hub, which then
  retransmits the data to the destination node
• Easily moved, isolated, or interconnected with
  other networks
• Scalable - Supports max of 1024 addressable nodes
  on logical network

A typical star topology network
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Star

• Any single cable connects only two devices
  Cabling problems affect two nodes at most
• More fault-tolerant
• Star advantages a break in the cable does not
  shut down the network higher reliability easier
  troubleshooting no terminators required
• Star disadvantages uses more cable than ring or
  bus networks hubs are more expensive than
  terminators hub failures take down entire LAN
  segments

The Star Topology Demo
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Hybrid Physical Topologies

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

Hybrid Topologies Demo
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Star-Wired Ring

• The star-wired ring topology uses the physical
  layout of a star in conjunction with the
  tokenpassing data transmission method. Data are
  sent around the star in a circular pattern. This
  hybrid topology benefits from the fault tolerance
  of the star topology (data transmission does not
  depend on each workstation to act as a repeater)
  and the reliability of token passing. Modern
  Token Ring networks, as specified in IEEE 802.5,
  use this hybrid topology.

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Star-Wired Ring
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) simply changes the
topology from a physical ring to a star wired
ring. The Token still circulates around the
network and is still controlled in the same
manner, however, using a hub or a switch greatly
improves reliability because the hub can
automatically bypass any ports that are
disconnected or have a cabling fault.
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Star-Wired Bus
A star-wired bus topology network
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Star-wired Bus

• In a star-wired bus topology, groups of
  workstations are star-connected to hubs and then
  networked via a single bus. With this design, you
  can cover longer distances and easily
  interconnect or isolate different network
  segments. One drawback is that this option is
  more expensive than using either the star or,
  especially, the bus topology alone because it
  requires more cabling and potentially more
  connectivity devices. The star-wired bus topology
  commonly forms the basis for modern Ethernet and
  Fast Ethernet networks.

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Advantages and Disadvantages of the different
network topologies
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Backbone Networks

• A network backbone is the cabling that connects
  the hubs, switches, and routers on a network.
  Backbones usually are capable of more throughput
  than the cabling that connects workstations to
  hubs. This added capacity is necessary because
  backbones carry more traffic than any other
  cabling in the network. For example, an
  increasing number of businesses are implementing
  fiber-optic backbone but continue to use CAT5
  wiring for the cabling from hubs to workstations.
  
• Although even the simplest LAN (including a star
  or bus topology LAN) technically has a backbone,
  enterprise-wide back-bones are more complex and
  more difficult to plan.
• The backbone is the most significant building
  block of these networks.

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Serial Backbone

• A serial backbone is the simplest kind of
  backbone network. It consists of two or more hubs
  connected to each other by a single cable. They
  are not suitable for large networks or long
  distances. Although the serial backbone topology
  could be used for enterprise-wide networks, it is
  rarely implemented for that purpose.
• Daisy chain linked series of devices
• Hubs and switches often connected in daisy chain
  to extend a network
• Hubs, gateways, routers, switches, and bridges
  can form part of backbone
• Benefit
• Logical growth solution
• Modular additions
• Low-cost LAN infrastructure
• expansion
• Easily attach hubs
• Serial connection of repeating devices
• Essential for distance communication
• Standards
• Define number of hubs allowed
• Exceed standards
• Intermittent, unpredictable data transmission
  errors

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Distributed Backbone

• Consists of a number of hubs connected to a
  series of central hubs or routers in a hierarchy
• Allows for simple expansion and limited capital
  outlay for growth
• Layers of hubs can be added to existing layers
• A more complicated distributed backbone connects
  multiple LANs or LAN segments using routers
• Provides network administrators with the ability
  to segregate workgroups and therefore manage them
  more easily
• Adapts well to an enterprise-wide network
  confined to a single building, where layers of
  hubs can be assigned according to the floor or
  department
• You must consider the maximum allowable distance
  between nodes and the server dictated by the
  network media
• Central point of failure is the hub at the
  uppermost layer
• Implementing can be relatively simple, quick, and
  inexpensive

A distributed backbone connecting multiple LANs
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Collapsed Backbone

• Uses a router or switch as the single central
  connection point for multiple sub-networks
• A single router or switch is the highest layer of
  the backbone.
• The dangers of using this arrangement relate to
  the fact that a failure in the central router or
  switch can bring down the entire network
• In addition, because routers cannot move traffic
  as quickly as hubs, using a router may slow data
  transmission.
• A substantial advantages is that this arrangement
  allows you to interconnect different types of
  sub-networks.
• You can also centrally manage maintenance and
  troubleshooting chores.

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Parallel Backbone

• The most robust enterprise-wide topology.
• This variation of the collapsed backbone
  arrangement consists of more than one connection
  from the central router or switch to each network
  segment.
• Each hub is connected to the router or switch by
  more than one cable.
• The advantage of using a parallel backbone is
  that its redundant (duplicate) links ensure
  network connectivity to any area of the
  enterprise.
• Parallel backbones are more expensive than other
  enterprise-wide topologies because they require
  much more cabling than the others. However, they
  make up for the additional cost by offering
  increased performance.
• As a network administrator, you might choose to
  implement parallel links to only some of the most
  critical devices on your network. By selectively
  implementing the parallel structure, you can
  lower connectivity costs and leave available
  additional ports on the connectivity devices.

Most Reliable and Most Expensive to Set UP
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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

Logical Topologies Demo
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Switching Circuit Switching

• Switching component of networks logical
  topology that determines how connections are
  created between nodes
• Circuit switching connection established between
  two network nodes before transmission
• Bandwidth dedicated to connection
• Remains available until communication terminated
• While connected, all data follows same path
  initially selected by switch
• Monopolizes bandwidth while connected
• Resource wasted
• Uses
• Live audio, videoconferencing
• Home modem connecting to ISP

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Message Switching

• Establishes connection between two devices,
  transfers information, then breaks connection
• Information then stored and forwarded from second
  device to third device on path
• Store and forward routine continues until
  message reaches destination
• All information follows same physical path
• Requires that each device in datas path have
  sufficient memory and processing power to accept
  and store information

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Packet Switching

• Breaks data into packets before transmission
• Packets can travel any network path
• Contain destination address and sequencing
  information
• Can attempt to find fastest circuit available
• When packets reach destination node, they are
  reassembled
• Based on control information
• Not optimal for live audio or video transmission
• Advantages
• No wasted bandwidth
• Devices do not process information
• Examples
• Ethernet networks
• Internet

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MPLS (Multiprotocol Label Switching)

• IETF
• Introduced in 1999
• Multiple layer 3 protocols
• Travel over any one of several connection-oriented
  layer 2 protocols
• Supports IP
• Common use
• Layer 2 WAN protocols
• Advantages
• Use packet-switched technologies over
  traditionally circuit switched networks
• Create end-to-end paths
• Act like circuit-switched connections
• Addresses traditional packet switching
  limitations
• Better QoS (quality of service)

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802.3 Ethernet
Ethernet Demo

• Ethernet is a LAN standard that specifies an
  implementation of the physical layer and the MAC
  sub-layer of the data link layer.
• An Ethernet network is a broadcast system this
  means that when a station transmits data, every
  other station receives the data. The frames
  contain a destination address in the frame header
  and only the station with that address will pick
  up the frame and pass it on to upper-layer
  protocols to be processed.
• The access method Carrier Sense Multiple
  Access/Collision Detection (CSMA/CD).

Ethernet/Fast Ethernet/Gigabit 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 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 compensate for them
• 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

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CSMA/CD (contd.)

• Collision domains differ from broadcast domains
• Ethernet cabling distance limitations
• Effected by collision domains
• Data propagation delay
• Time for data to travel
• From one segment point to another point
• Too long
• Cannot identify collisions accurately
• 100 Mbps networks
• Three segment maximum connected with two hubs
• 10 Mbps buses
• Five segment maximum connected with four hubs

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Collision Domain

• On an Ethernet network, an individual segment is
  known as a collision domain, or a portion of a
  network in which collisions will occur if two
  nodes transmit data at the same time.
• The more nodes transmitting data on a network,
  the more collisions will take place and you may
  see performance suffer as a result of collisions.
• Collisions are likely to occur at the Physical
  Layer (on the channel or wire).
• Repeaters and Hubs are Physical Layer devices and
  therefore share the Ethernet channel.
• Portions of the network connected by repeaters or
  hubs must share the bandwidth of the single
  Ethernet channel.
• Repeaters/Hubs simply regenerate any signal they
  receive, they repeat collisions just as they
  repeat data.
• Networks can be separated into multiple
  collisions domains by using switches.

Collision Domains Demo
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10BASE-T

• The 10 represents its maximum throughput of
  10Mbps, the Base indicates that it uses
  baseband transmission, and the T stands for
  twisted pair, the medium it uses.
• On a 10BaseT network, one pair of wires in the
  UTP cable is used for transmission, while a
  second pair of wires is used for reception. By
  using two pairs of wires, 10BaseT networks use
  full-duplex transmission.
• A 10BaseT network requires CAT3 or higher UTP.
• Fault tolerance capacity for component or system
  to continue functioning despite damage or partial
  malfunction
• Physical star configuration
• Maximum cable length is 100 meters
• Nodes connected via concentrator
• Maximum of 1024 Nodes per logical segment
• Passive Topology connect to Active Hubs
• No external terminators
• 10Base-T Advantages 1) the star wiring topology
  supports easier maintenance and troubleshooting,
  2) twisted pair wiring is inexpensive and widely
  used, and 3) optionally supports full-duplex
  operation.

BASE Terminology Demo
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10BASET 5-4-3 Rule
5-4-3 rule of networking between two
communicating nodes, network cannot contain more
than five network segments connected by four
repeating devices, and no more than three of the
segments may be populated
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100BaseT Ethernet

• 100Base-T (Fast Ethernet)
• IEEE 802.3u standard
• Similarities with 10Base-T
• Baseband transmission, star topology, RJ-45
  connectors
• Requires CAT5 or higher UTP
• Supports three network segments maximum
• Connected with two repeating devices
• 100 meter segment length limit between nodes
• Maximum of 1024 Nodes per logical segment
• 100Base-TX
• 100-Mbps throughput over twisted pair
• Full-duplex transmission doubles effective
  bandwidth

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1000BaseT Gigabit Ethernet

• 1000BASE-T or 802.3ab is a standard for Gigabit
  Ethernet over copper wiring. It requires, at a
  minimum, Cat 5e ("Category 5 enhanced") cable.
  Category 6 cable may also be used. The 1000BASE-T
  standard was approved by the IEEE 802.3 in 1999.
• In a departure from both 10BASE-T and 100BASE-TX,
  1000BASE-T uses all four cable pairs to achieve
  full duplex transmission. The aggregate data rate
  of 1000 Mb/s is achieved by transmission at a
  data rate of 250 Mb/s over each wire pair.
• Each network segment can have a maximum distance
  of 100 meters. This usually consists of 90 m
  horizontal (inside the building), 9 m at the
  patch panel, and 1 m from the port to the
  computer or node.
• 1000BaseT buses can practically support a maximum
  of two network segments connected with one hub
  and 1024 nodes per logical segment.

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10GBaseT Ethernet

• 10GBase-T
• IEEE 802.3an
• 10GBASE-T cable infrastructure can also be used
  for 1000BASE-T allowing a gradual upgrade from
  1000BASE-T
• Pushing limits of twisted pair
• Requires Cat 6 or Cat 7 cabling
• Maximum segment length 100 meters
• Benefit
• Very fast data transmission, lower cost than
  fiber-optic
• Use
• Connect network devices
• Connect servers, workstations to LAN

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100Base-FX Ethernet

• 100Base-FX supports a 100 Mb/s transmission rate
  over two multimode fiber optic cables. One cable
  is used to transmit data, and the other is used
  to receive data.
• It allows maximum segment lengths of 412 meters
  for half-duplex links, and 2000 meters or more
  for full-duplex links.
• The 100Base-FX standard allows several types of
  fiber optic connectors to be used. Duplex "SC"
  connectors are recommended, but "ST" and FDDI
  "MIC" connectors are also permitted.
• In full-duplex mode, 100Base-FL segment lengths
  can be increased from 412 meters to 2000 meters.
  Even longer distances can be supported with the
  more expensive single mode fiber (SMF).
• The 100BaseFX standard uses a star topology, with
  its repeaters connected through a bus with a
  maximum of two repeaters allowed to connect three
  segments.

2000
2000 Full duplex
2000
Full duplex
6000
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1000Base-LX Ethernet

• 1000Base-LX operates with a 1300nm laser over
  single and multi-mode fiber
• The "L" in 1000Base-LX stands for "long" as it
  uses long wavelength lasers to transmit data over
  fiber optic cable.
• Long wavelength lasers are more expensive than
  short wavelength, but have the advantage of being
  able to drive longer distances.
• Maximum segment lengths range from 550 meters
  using multimode fiber to 5000 meters using single
  mode.
• One repeater may be used to connect two segments.
• Excellent choice for long backbones

550m using MMF to 5000m using SMF
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1000Base-SX Ethernet

• 1000BASE-SX is a fiber optic gigabit Ethernet
  standard.
• The "S" in 1000Base-SX stands for "short" as it
  uses short wavelength lasers to transmit data
  over fiber optic cable. The short wavelength
  lasers specified by the standard operate at 850
  nanometers. Less expensive than long wavelength
  lasers.
• Only multi-mode optical fiber is supported.
• Maximum segment lengths range from 275 meters
  (62.5 micron fibers) to 550 meters (50 micron
  fibers) depending on the diameter of the fiber
  used.
• Only one repeater may be used between two
  segments.
• Best suited for shorter network runs

275 to 550 meters
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10Gigabit Ethernet (802.3ae)

• The IEEE 802.3ae standard specifies 10Gigabit
  Ethernet, also referred to as 10GbE, over
  multimode and single-mode fiber optics.
• 10GbE increases the maximum fiber optic cable
  lengths up to 40 kilometers.
• All use SC or LC connectors.
• Common characteristics
• Star topology, allow one repeater, full-duplex
  mode
• Differences
• Signals light wavelength, maximum allowable
  segment length

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10GBase-SR and 10GBase-SW

• 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
• 300 meters using 50 micron fiber
• 66 meters using 62.5 micron fiber

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10GBase-LR and 10GBase-LW

• 10GBase-LR and 10GBase-LW
• 10G 10 Gbps
• Base baseband transmission
• L long reach
• Single-mode fiber 1319 nanometer signal
  transmission
• Maximum segment length
• 10,000 meters
• 10GBase-LR WAN or MAN
• 10GBase-LW SONET WAN links

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10GBase-ER and 10GBase-EW

• 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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Summary of Common Ethernet Standards
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Ethernet Frames

• Ethernet networks may use one (or a combination)
  of four kinds of data frames
• Ethernet_802.2 (Raw)
• Ethernet_802.3 (Novell proprietary)
• Ethernet_II (DIX)
• Ethernet_SNAP
• Frame types differ in way they code and decode
  packets of data
• Ethernet frame types have no relation to
  networks topology or cabling characteristics

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Using and Configuring Frames

• Cannot expect interoperability between frame
  types
• Nodes Data Link layer services must be properly
  configured for types of frames it might receive
• LAN administrators must ensure all devices use
  same, correct frame type
• Most networks use Ethernet_II
• Frame types typically specified through devices
  NIC configuration software
• (AutoSense) Most NICs automatically sense frame
  types running on network and adjust

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Frame Fields

• Ethernet frame types share many common fields
• Every frame contains
• 7-byte preamble and 1-byte start-of-frame
  delimiter (SFD)
• 14-byte header
• Destination address
• Source address
• Additional field that varies in function and size
• 4-byte FCS field
• Data portion
• 46 to 1500 bytes of information

Ethernet_II (DIX) frame
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Summary

• A physical topology is the basic physical layout
  of a network it does not specify devices,
  connectivity methods, or addresses on the network
• A bus topology consists of a single cable
  connecting all nodes on a network without
  intervening connectivity devices
• In a star topology, every node on the network is
  connected through a central device, such as a hub
• LANs often employ a hybrid of more than one
  simple physical topology
• Network backbones may follow serial, distributed,
  collapsed, or parallel topologies
• Ethernet employs a network access method called
  CSMA/CD
• Networks may use one (or a combination) of four
  kinds of Ethernet data frames

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The End