Ethernet Basic, Coaxial Cable Based Ethernet Technologies (10Base5 and 10Base2)

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Chapter 5

• Ethernet Basic, Coaxial Cable Based Ethernet
  Technologies (10Base5 and 10Base2)

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What is the Ethernet?

• Ethernet
• A family of network technologies (standards)
• Logical bus topology
• Bus physical topology The older Ethernet
• Star physical topology The newer Ethernet
  (Star Bus topology)

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What is the Ethernet?

• Ethernet
• Ethernet frame
• CSMA/CD as the network access method/media access
  control, i.e., a method to determine which
  computer in the network can access the wire (in
  the network) at a given moment

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Ethernet in the OSI 7 layer model
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Ethernet Frame

• Ethernet frame
• Created, sent, received, read, and destroyed by
  Ethernet NIC
• The advantages of using frame
• Frame defines the maximum data size, and
  therefore, large data must be broken into smaller
  pieces. This provides two benefits
• Benefit 1 Preventing one computer from
  monopolizing the shared wire in the network
  (distributing the network use among all computers
  in the network more evenly)
• Benefit 2 Whenever data is corrupted during
  transmission, the sending computer only has to
  retransmit one (or few) frame(s) that contains
  the corrupted data

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Ethernet Frame

• Seven major parts in Ethernet frame
• Part 1 Preamble
• 64 bits of alternating 1s and 0s and ends with 11
• Functions
• Enabling the receiving NIC to recognize the
  beginning of a frame
• Giving time to the receiving NIC to realize a
  coming of a frame and therefore, can make all
  necessary preparations to receive the frame
  properly

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Ethernet Frame

• Seven major parts in Ethernet frame
• Part 2 and 3 Receiver/destination MAC address
  and Sender MAC Address
• Whenever a computer in a network (NODE) sends a
  frame to the network, the frame will be sent to
  EVERY OTHER NODE in the network
• Whenever a computer (NIC) receives a frame, it
  will first examine the destination MAC address
• If the destination MAC address in a frame is the
  same as the computers (NICs) MAC address, the
  computer (NIC) will process the frame further
• If different, the computer (NIC) will destroy the
  frame
• A program/software called SNIFFER can enable NIC
  to run in PROMISCUOUS MODE to process ALL frames
  it receives, regardless of their destination MAC
  addresses
• http//support.microsoft.com/kb/812953
• http//www.tamos.com/htmlhelp/monitoring/monitorin
  gusinghubs.htm

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Sniffer, Promiscuous Mode
Frame For Computer 3
Computer 1
Computer 2
Computer 3
Computer 6
Computer 4
Computer 5
Destroy the Frame
Destroy the Frame
Destroy the Frame
Process the Frame
NOT the Intended Receiver, BUT Process the Frame
if Running Sniffer
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Ethernet Frame

• Seven major parts in Ethernet frame
• Part 4 Length
• Information about the number of BYTES of DATA
  inside the frame
• Minimum number of bytes of data 46 bytes
• Maximum number of bytes of data 1500 bytes
• Part 5 Data
• Data that is received from the upper layer of the
  OSI seven-layer model (Network Layer) PACKET
• Minimum number of bytes of data 46 bytes
• Maximum number of bytes of data 1500 bytes

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Ethernet Frame

• Seven major parts in Ethernet frame
• Part 6 Pad
• Minimum number of bytes of data 46 bytes
• If the data size is less than 46 bytes, the
  sender will add more bytes in this part (PAD) to
  bring the data up to the minimum 46 bytes
• Part 7 Frame Check Sequence
• Error Detection Information (CRC for the
  Ethernet)
• To detect data transmission error that causes
  data modification during the transmission

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Ethernet Frame
FCS (Frame Check Sequence) IEEE 802.3 version
of CRC
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CSMA/CD

• Carrier Sense Multiple Access (CSMA)/Collision
  Detection (CD)
• Network access method (media access control)
• Carrier Sense
• Every computer in the network must first examine
  (sense) the BUS/SEGMENT before sending a frame
• If the computer detects traffic in the
  BUS/SEGMENT, it will wait for a moment, and then
  reexamine (resense) the BUS/SEGMENT
• If the computer detects no traffic, it will send
  the frame to the BUS/SEGMENT

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CSMA/CD

• Multiple Access
• All computers in a network have equal access to
  the wire (no computer has greater access
  (priority) to access the wire)
• Collision Detection
• When two or more computers are sending frames to
  a BUS/SEGMENT simultaneously, a collision occurs,
  and all frames will be corrupted/damaged/lost
  (the transmission is wasted)
• During a frame transmission (after sending a
  frame to a BUS/SEGMENT), the senders NIC will
  always monitor (listen to) the BUS/SEGMENT
• If the senders NIC detects another frame being
  transmitted in the BUS/SEGMENT, it recognizes
  that its frame has been corrupted by collision
  with another frame

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Collision Domain

• Collision Domain
• A segment/part in a network in which there will
  be collision if two or more computers in this
  segment/part both transmit frames simultaneously
• Collisions can significantly slow down the
  network. Why? Because every time there is a
  collision, the sender will automatically
  retransmit the frame (the original transmission
  is wasted)
• A SWITCH or BRIDGE (i.e., a two-port switch) can
  divide a network into multiple collision domains

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Switch
Computer A
For Computer B
Switch
Computer B
Accept the message
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Switch (Bridge) to Break a Network in Multiple
Collision Domains
Frame For Computer 3
Collision domain 1
Collision domain 2
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Collision Domain

• FAQ
• Can I break a network into multiple collision
  domains by using a Router?
• Yes, you can
• So, why do I use Switch instead of a Router?
• Switch is cheaper (although the price of Router
  continues going down)
• Switch is easier to install (e.g., no (not much)
  configuration is needed)

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Ethernet technologies

• Ethernet is a family of network technologies that
  use the same bus logical topology, the Ethernet
  frame, the same network access method (CSMA/CD)
• Three classes of Ethernet technology
• Coaxial Cable Based Ethernet (Use Coaxial Cable)
• Thick Ethernet (Thicknet) 10Base5
• Thin Ethernet (Thinnet) 10Base2
• UTP Based Ethernet (Use UTP/Unshielded Twisted
  Pair cable)
• 10BaseT
• 100BaseTX
• Fiber-Optic Cable Based Ethernet (Use Fiber-Optic
  cable)
• 100BaseFX

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(OLD) Coaxial Cable Based Ethernet

• Thick Ethernet (Thicknet) 10Base5
• Thin Ethernet (Thinnet) 10Base2
• The oldest Ethernet technologies
• Using coaxial cable as the bus cable
• Physical Bus and Logical Bus topology

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Thick Ethernet

• Thick Ethernet (Thicknet)
• RG-8 coaxial cable as the BUS (SEGMENT)
• Each computer is connected to the RG-8 BUS CABLE
  (SEGMENT) by using Attachment Unit Interface
  (AUI) cable and TRANSCEIVER
• AUI cable is also known as Transceiver cable
  (Transceiver Drop cable)

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Thick Ethernet
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Thick Ethernet
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10Base5 (Thick Ethernet, Thicknet)

• Thick Ethernet (Thicknet) is also known as
  10Base5
• 10 Data transmission speed/rate/bandwidth/through
  put 10 Mbps
• Base Baseband A single cable can carry only one
  signal
• 5 a BUS/SEGMENT cannot be longer than 500 meters
  (without repeater)

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Bits versus Bytes

• 1 Byte contains 8 bits
• 1 B 8 b
• A single character is represented by 8 bit code
  (1 Byte code)
• B is used to measure storage capacity (B, MB, GB)
• b is used to measure data transmission speed/rate
  (bps, mbps)

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Baseband versus Broadband

• Baseband
• A single cable can carry only one signal at any
  time (a single channel in a single cable at any
  time)
• Broadband
• A single cable can carry multiple signals at any
  time (multiple channels in a single cable at any
  time)

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10Base5

• How to build a 10Base5 network?
• Step 1 Install 10Base5 NICs in ALL computers in
  the network
• Step 2 Create an RG-8 BUS/SEGMENT (installing
  TERMINATORS at the two ends of an RG-8 cable)
• Step 3 To connect a 10Base5 NIC to the
  BUS/SEGMENT,
• Install a TRANSCEIVER in the BUS/SEGMENT
• Use AUI cable to connect the NIC to the
  TRANSCEIVER

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10Base5

• Things to remember during installation
• TRANSCEIVER must be installed at any one of the
  2.5-meter intervals along the RG-8 BUS/SEGMENT
• AUI cable can be up to 50 meters
• The BUS/SEGMENT (without repeater) can be up to
  500 meters
• Up to 100 computers can be attached to a
  BUS/SEGMENT (without repeater)

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10Base5
Bus length Maximum 500 meters
Multiples of 2.5 meters
Multiples of 2.5 meters
? 50 meters
? 50 meters
? 50 meters
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Thin Ethernet

• Thin Ethernet (Thinnet)
• RG-58 bus cable
• Computers are connected to the RG-58 bus cable by
  using BNC (Bayonet-Neill-Concelman) Connectors

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10Base2
BNC Connector
BNC T-Connector
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10Base2
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10Base2 (Thin Ethernet, Thinnet)

• Thin Ethernet (Thinnet) is also known as 10Base2
• 10Base2
• 10 data transmission speed/rate/throughput/bandwi
  dth 10 Mbps
• Base Baseband method
• 2 the BUS/SEGMENT cannot be longer than 185
  meters

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10Base2 versus 10Base5

• Advantages of 10Base2
• Cheaper to install RG-58 cable is cheaper than
  RG-8 cable no need for Transceiver and AUI cable
• Easier to install
• Computers must be installed at least 0.5 meters
  apart, but they do not have to be spaced at
  specific intervals as required by 10Base5 no
  need to install Transceiver and AUI cable
• Disadvantage of 10Base2
• Maximum 30 computers/NICs per BUS/SEGMENT
• Maximum coverage only 185 meters

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Bus and Repeater

• ATTENUATION refers to a reduction in the strength
  of a signal
• The longer the distance the signal has traveled,
  the weaker the signal becomes
• Repeater can regenerate the original signal

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How Many Repeaters can be Used in an Ethernet
Network?

• Ethernets 5-4-3 Rule
• 5 Maximum of 5 bus cables/segments
• 1 segment 10Base5 RG-8 bus cable, max 500
  meters
• 1 segment 10Base2 RG-58 bus cable, max 185
  meters
• 4 Maximum of 4 repeaters
• 3 Only 3 segments (out of maximum of 5) can have
  computers attached (maximum of 3 populated
  segments)

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How Many Repeaters can be Used in an Ethernet
Network?

• The 5-4-3 rule in 10Base5 network
• 5 bus cables (segments) - 4 repeaters - 3 bus
  cables (segments) with computers connected

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How Many Repeaters can be Used in an Ethernet
Network?
The 5-4-3 rule in 10Base2 network
5 bus cables (segments) - 4 repeaters - 3 bus
cables (segments) with computers connected
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Extending a Network

• To connect computers gt 500 meter apart for RG-8,
  or gt 185 meter apart for RG-58
• Extend the network
• Repeaters
• Switches (bridges)
• The disadvantages of extending a network with
  repeaters
• At any time, there is only one computer that can
  access the network
• The more computers, the more probability of
  collision
• Maximum of 4 repeaters

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Switch/Bridge

• Bridge switch with TWO ports only
• Bridge has the same functions as switch

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Repeater versus Bridge
Frame For Computer 3
Destroy the Frame
Destroy the Frame
Destroy the Frame
Destroy the Frame
Process the Frame
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Repeater versus Bridge
Frame For Computer 3
Destroy the Frame
Process the Frame
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Switch (Bridge)

• Switch (bridge) functions
• Breaking the network into multiple collision
  domains
• Enabling more efficient data communication (to
  allow more than one computer to send frames to
  the network/to use the network at the same time)
• Reducing the possibility of collisions
• As many switches/bridges as required

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A Switch (Bridge) Breaks a Network into Multiple
Collision Domains
Collision Domain 1
Collision Domain 2
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The use of unpopulated segment

• What is the use of having unpopulated segment
  (i.e., segment that has NO computer attached on
  it)?
• To extend the network (an extension cable)

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Hub (repeater) versus Switch (bridge) versus
router

• When do we use hub (repeater), switch (bridge),
  and router?
• Hub
• Switch
• Router
• Router can do what a switch can do, but it is
  more expensive and more difficult to install
  (e.g., requires more configuration).
• If you want to install packet sniffer to monitor
  incoming traffics to your network, get hub

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