CS 2200

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CS 2200

• Presentation 21
• Networking

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(No Transcript)
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Questions?
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Our Road Map
Processor
Memory Hierarchy
I/O Subsystem
Parallel Systems
Networking
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Overview

• Today
• A Brief History
• Basic Concepts
• Network Hardware
• Ethernet
• Network Protocols
• Distributed Systems
• Remote Procedure Calls (RPC)

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A Brief History

• 1876 Telephone Invented
• (Analog technology)
• 1942 Mainframes Developed
• Use continues today
• Initially batch oriented environment
• Evolution to Timesharing
• i.e. Data terminals connected to mainframes
• Early 60's Voice telephony switches to digital

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A Brief History

• 1960 ATT Introduced Dataphone
• First commercial modem
• Modem Modulator/Demodulator
• Convert between digital and analog signals
• (Essentially same technology used today)

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A Brief History

• 1965 DoD Advanced Research Projects Association
  begins work on ARPANET
• 1968/9 Carterphone decision allowed devices which
  were beneficial and not harmful to the network to
  be connected to the Public Switched Telephone
  Network (PSTN).
• Paved the way for computers to communicate using
  the telephone switching infrastructure.

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A Brief History

• 1969 ARPANET connects 4 computers
• Stanford Research Institute, UCLA, UC Santa
  Barbara, and the University of Utah
• 1971 The ARPANET grows to 23 hosts connecting
  universities and government research centers
  around the country.
• 1971 Intel introduces the first microprocessor -
  the Intel 4004.

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A Brief History

• 1971 The Kenbak-1, the first microcomputer, is
  introduced in Scientific American, selling a
  total of 40 units in 2 years.
• Used 130 IC's with a 256 byte memory and 8-bit
  words, processed 1000 instructions per second,
  and cost 750.

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A Brief History

• 1972 Intel launches the 8-bit 8008 - the first
  microprocessor which could handle both upper and
  lowercase characters.
• 1972 Xerox develops the Xerox Alto - the first
  computer to use a Graphic User Interface.

The Alto consists of four major parts the
graphics display, the keyboard, the graphics
mouse, and the disk storage/processor box. Each
Alto is housed in a beautifully formed, textured
beige metal cabinet that hints at its 32,000
price tag (1979US money). With the exception of
the disk storage/processor box, everything is
designed to sit on a desk or tabletop
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A Brief History

• 1973 Robert Metcalfe invents the Ethernet
  networking system at the Xerox Palo Alto Research
  Center.

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A Brief History

• 1973 The ARPANET goes international
• 1974 Intel introduces the 8080 microprocessor
• 5 times faster than the 8008.
• And the heart of the future Altair 8800.

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A Brief History

• 1975 MITS markets the Altair 8800 - the first
  mass-market microcomputer, launching the Personal
  Computer Revolution.
• 1975 Internet operations transferred to the
  Defense Communications Agency
• 1975 Bill Gates and Paul Allen form the Microsoft
  company to create software for the new Altair
  8800.

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A Brief History

• 1976 Apple Computer is formed by Steve Jobs,
  Steve Wozniak, and Ron Wayne, and launches the
  Apple Computer.
• 1977 Tandy Radio Shack ships its first personal
  computer - the TRS-80. It sells over 10,000
  units, tripling expectations.
• 1977 Apple Computer launches the Apple II, which
  sets new standards for sophisticated personal
  computer systems.

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A Brief History

• 1978 The C programming language is completed at
  ATT Bell Laboratories, offering a new level of
  programming.
• 1978 Apple and Tandy ship PCs with 5.25" floppy
  disks, replacing cassette tape as the standard
  storage medium for PCs.
• 1978 Hayes Microcomputer Products releases the
  first mass-market modem, transmitting at 300 bps
  (0.3K).

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A Brief History

• 1978 Intel ships the Intel 8086 microprocessor,
  with 29,000 transistors, and running at 4.77
  megahertz.
• 1979 Personal Software creates VisiCalc for the
  Apple II, the first electronic spreadsheet
  program, selling over 100,000 copies.
• 1979 Intel develops the 8088 microprocessor,
  which would later become the heart of the IBM PC.

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A Brief History

• 1979 Motorola develops the Motorola 68000
  microprocessor, offering a new level of
  processing power.
• 1980 Seagate Technology introduces the first
  microcomputer hard disk, capable of holding 5
  megabytes of data.
• 1980 Philips introduces the first optical laser
  disk, with many times the storage capacity of
  floppy or hard disks.

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A Brief History

• 1980 Xerox creates Smalltalk - the first
  object-oriented programming language.
• 1980 John Shoch at Xerox creates the first worm
  program, with the capacity to travel through
  networks.
• 1981 Ungermann-Bass ships the first commercial
  Ethernet network interface card.

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A Brief History

• 1981 Xerox introduces the Xerox Star 8010, the
  first commercial Graphic User Interface computer,
  for 16,000-17,000.
• 1981 Microsoft supplies IBM with PC-DOS (which it
  would also sell as MS-DOS), the OS that would
  power the IBM PC.
• 1981 IBM brings to market the IBM PC, immediately
  establishing a new standard for the world of
  personal computers.

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A Brief History

• 1981 ARPANET has 213 hosts. A new host is added
  approximately once every 20 days.
• 1982 The term 'Internet' is used for the first
  time.
• 1983 TCP/IP becomes the universal language of the
  Internet

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http//research.lumeta.com/ches/map/
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Question

• That last group of slides was swell
• Strongly agree
• Agree
• Neutral
• Disagree
• Strongly Disagree

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Types of Interconnections

• Massively Parallel Processors (MPP)
• Thousands of nodes
• Short distances
• Local Area Networks (LAN)
• Hundreds of computers
• Several kilometers
• Traffic many to one (clients to servers)
• Wide Area Network (WAN)
• Thousands of computers
• Thousands of kilometers
• Scalable

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Types of Interconnections

• Massively Parallel Processors (MPP)
• Tightly coupled
• Share memory and sometimes clock
• Local Area Networks (LAN)
• Wide Area Network (WAN)
• Loosely coupled
• Do not share memory and clock
• Each processor has its own local memory
• Communication via networks

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Basic Concepts
Machine A
Machine B
Each machine has the ability to send a message to
the other a.) Please send me the contents of
address x b.) Here is the contents of address
x Thus, messages must contain an extra bit.
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Basic Concepts
Payload (32 bits)
Header (1 bit)
0
Address
0-Request 1-Reply
1
Data

• Messages are divided into parts
• Payload or actual data to be transferred
• Header (or trailer) data used to control the
  message passing scheme
• System must be designed to work well with
  operating system.
• Multiple Processes
• Error Handling

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Software Steps to Send

• Application copies data into O.S. buffer
• Operating System
• Calculates checksum
• Includes checksum in header and/or trailer
• Starts timer
• Sends data to network interface hardware and
  tells it to send message
• Wait...

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Reception

• Copy data from network hardware into operating
  system buffer
• Calculate checksum from data
• If calculated checksum matches included checksum
• Send acknowledgement
• Copy data into application space
• Else
• Discard message
• Wait for resend

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Sender...

• If acknowledgement arrives
• Discard copy of message in buffer
• If timer times out first
• Resend data
• Restart timer

Header (2 bits) 00Request 01Reply 10Acknowledge
Request 11Acknowledge Reply
Payload Data (32 bits)
Checksum (4 bits)
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Protocols

• Sequence of steps performed by software to send
  and receive messages.
• Issues
• Endianess
• Duplicate messages
• Queue full
• etc.
• More next time...

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There is an old network saying Bandwidth
problems can be cured with money. Latency
problems are harder because the speed of light is
fixed--you cant bribe God.

• David Clark, MIT

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Vocabulary Fun

• Bandwidth
• Time of Flight
• Transmission Time
• Transport Latency
• Sender Overhead
• Receiver Overhead

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Diagramatically
Sender Overhead
Transmission Time
Sender
Time of Flight
Reception Time
Receiver Overhead
Receiver
Transport Latency
Total Latency
TIME
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Questions?
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Questions?

• Where do you connect the network to the computer?
• Which media are available to connect computers
  together?
• What issues arise when connecting more than two
  computers
• Additional practical issues?

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Connecting the Computer

• Connection Point
• Memory Bus
• I/O Bus
• Control
• Polling
• Interrupts
• Operating System Involvement

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Connecting the Computer

• Connection Point
• Memory Bus MPP
• I/O Bus LAN/WAN
• Control
• Polling Hybrid
• Interrupts Approaches
• Operating System Involvement
• Avoid invoking O.S. in common case

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Hierarchy of Media

• Twisted Pair
• Coaxial Cable
• Fiber Optics

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Question

• Why is twisted pair twisted?
• Keeps cable from kinking i.e. adds strength
• Avoids electromagnetic interference
• Keeps matching pairs grouped together in large
  bundle cables
• Invented by Dee Snyder

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Media

• Twisted Pair
• 1 Mb/Sec 2 km 0.23/m 15
• 20 Mb/sec 0.1 km 0.23/m
• Coaxial Cable
• 10 Mb/sec 1 km 1.64 460
• Multimode Fiber
• 600 Mb/sec 2 km 1.03 2000
• Single-Mode Fiber
• 2000 Mb/sec 100 km 1.64 2000

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Questions?

• So far how many computers have we connected?

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Connecting gt 2

• Shared Media
• Bus
• Ethernet (Vampire Taps)
• Coordination Mechanism
• Carrier Sensing and Collision Detection
• Broadcast
• Switched Media
• Better utilization of bandwidth
• Point to point

Node
Node
Node
Node
Node
Node
Switch
Node
Node
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More About Rings

• Token Ring
• Nodes pass token from one to another
• When you have token you can send

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Comparison

• Ethernet
• CSMA/CD allows any node to talk at any time
  unless two talk at the same time
• Efficient at low loads
• As the number of hosts increases performance
  degrades

• Token Ring
• Token being passed around ring only allows node
  holding token to talk
• Less efficient than Ethernet at low loads
• As number of nodes increases performance slows
  but performance is predictable

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Connection vs. Connectionless

• Phone System
• To make call a connection or circuit was
  connected (might be multiplexed).
• Not a bad idea for voice
• Connection exists whether or not anyone is
  talking.
• Limit is number of conversations NOT amount of
  data
• Postal System
• Each piece of information is routed according to
  its address
• Long messages can be broken up into pieces or
  packets (or frames).

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Project 5

• Due Friday, December 5th at
• 115959 pm EST
• HONEST!!!

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Routing

• Shared Media
• Message goes to all nodes. Each looks at address
  to determine if they are recipient
• Switched Media
• Source-based routing
• Message specifies path to destination
• Virtual circuits
• Temporary or permanent
• Destination-based routing
• Deterministic
• Adaptive
• Random

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Routing Policies

• Store and Forward
• Wormhole
• http//www.cc.gatech.edu/bleahy/janet/

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Congestion Control

• Circuit switched
• All circuits are busy
• Packet switched
• Deadlock
• Reducing Congestion
• Packet discarding!
• Flow control (Window used by TCP)
• Choke packets

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Questions?
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The Ethernet
A drawing of the first Ethernet system by Bob
Metcalfe.
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Ethernet Evolution

• X_Base_Y
• X stands for the available media bandwidth
• Base stands for base band signaling on the medium
• Y stands for the maximum segment length

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Ethernet Evolution

• 10_base_5 (1979-1985)
• 10 Mbits/Sec with base band signaling with a
  maximum station distance of 500 meters
• Thick shielded copper conductor used as the medium

MAU-Medium Access Unit
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• 10_base_2 (1985-1993)
• Thin net, cheaper net
• Distance to the station shrinks to 200 meters
• No more vampire taps
• BNC connector to connect the stations to the
  Attach Unit Interface (AUI) cables, the AUI
  cables to the medium
• The medium is daisy-chained via the stations
  using the BNC connectors

Bayonet Neil-Concelman, or sometimes British
Naval Connector
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• 10_base_T (1993-1995)
• Attach Unit Interface (AUI) is a twisted pair of
  copper wires
• AUIs from the stations come to a hub which is a
  multiplexor/transceiver
• Did away with the BNC connectors which were a
  source of connector problems
• Use phone jack technology (RJ45 connectors) to
  connect AUI cables to the hub
• Hubs are connected to other hubs using the same
  connectors (RJ45)

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• 10_base_T (1993-1995) continued
• All the hubs together form the entire medium
• All the stations in the same collision domain
• Hub is also usually called a repeater

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More Ethernet

• 10BROAD36 - 10BROAD36 is a seldom used Ethernet
  specification which uses a physical medium
  similar to cable television, with CATV-type
  cables, taps, connectors, and amplifiers.
• 1BASE5 - 1BASE5 is a specification of Ethernet
  that runs at 1 Mb/s over twisted pair wiring.
  This physical topology uses centralized hubs to
  connect the network devices.
• FOIRL - Fiber Optic Inter-Repeater Link - This
  specification of the 802.3 standard defines a
  standard means of connecting Ethernet repeaters
  via optical fiber.

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More Ethernet

• 10BASE-F - 10BASE-F is a set of optical fiber
  medium specifications which define connectivity
  between devices.
• 100BASE-T - 100BASE-T is a series of
  specifications that provides 100 megabit speeds
  over copper or fiber. These topologies are often
  referred to as Fast Ethernet.
• Gigabit Ethernet - Gigabit Ethernet provides
  speeds of 1000 Mb/s over copper and fiber.

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Where will it end???
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Broadband vs. Baseband

• A baseband network has a single channel that is
  used for communication between stations. Ethernet
  specifications which use BASE in the name refer
  to baseband networks.
• A broadband network is much like cable
  television, where different services communicate
  across different frequencies on the same cable.
• Broadband communications would allow a Ethernet
  network to share the same physical cable as voice
  or video services. 10BROAD36 is an example of
  broadband networking.

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Current Technology

• Most modern Ethernet networks use twisted pair
  copper cabling or fiber to attach devices to the
  network. The 10BASE-T, 100BASE-T, and Gigabit
  Ethernet topologies are well suited for the
  modern cabling and fiber infrastructures.

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Still Hungry?

• http//www.faqs.org/faqs/LANs/ethernet-faq/

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Ethernet

• The various Ethernet specifications include a
  maximum distance
• What do we do if we want to go further?
• Repeater
• Hardware device used to extend a LAN
• Amplifies all signals on one segment of a LAN and
  transmits them to another
• Passes on whatever it receives (GIGO)
• Knows nothing of packets, addresses
• Any limit?

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Repeaters
R1
R2
R3
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Repeaters
R1
R2
R3
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Bridges

• We want to improve performance over that provided
  by a simple repeater
• Add functionality (i.e. more hardware)
• Bridge can detect if a frame is valid and then
  (and only then) pass it to next segment
• Bridge does not forward interference or other
  problems
• Computers connected over a bridged LAN don't know
  that they are communicating over a bridge

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Bridges

• Typical bridge consists of conventional CPU,
  memory and two NIC's.
• Does more than just pass information from one
  segment to another
• A bridge can be constructed to
• Only pass valid frame if necessary
• Learn what is connected to network "on the fly"

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Bridges

• Event Segment 1 List Segment 2 List
• Bridge boots - -
• U send to V U -
• V sends to U U, V -
• Z broadcasts U, V Z
• Y sends to V U, V Z, Y
• Y sends to X U, V Z, Y
• X sends to W U, V Z, Y, X
• W sends to Z U, V, W Z, Y, X

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Bridges

• A bridge will connect to distinct segments
  (usually referring to a physical length of wire)
  and transmit traffic between them.
• This allows you to extend the maximum size of the
  network while still not breaking the maximum wire
  length, attached device count, or number of
  repeaters for a network segment.

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Switch
A
B
C
D
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Virtual LANs

• VLANs may span bridges
• Nodes 1 and 5 same VLAN 2, 6, 7 same VLAN
• All nodes on the same VLAN hear broadcasts from
  any node on that VLAN
• VLAN limits the traffic flow among bridges
• A hierarchical network with only bridges results
  in a switched ethernet with no collisions!

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http//www.cisco.com/univercd/cc/td/doc/product/so
ftware/ios113ed/113ed_cr/switch_c/xcvlan.htm
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Network Interface Card

• NIC
• Sits on the host station
• Allows a host to connect to a hub or a bridge
• If connected to a hub, then NIC has to use
  half-duplex mode of communication (i.e. it can
  only send or receive at a time)
• If connected to a bridge, then NIC (if it is
  smart) can use either half/full duplex mode
• Bridges learn Media Access Control (MAC) address
  and the speed of the NIC it is talking to.

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Routers

• Work much like bridges
• Pay attention to the upper network layer
  protocols
• (OSI layer 3) rather than physical layer (OSI
  layer 1) protocols.
• Will decide whether to forward a packet by
  looking at the protocol level addresses (for
  instance, TCP/IP addresses) rather than the MAC
  address.

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Routers

• Because routers work at layer 3 of the OSI stack,
  it is possible for them to transfer packets
  between different media types (i.e., leased
  lines, Ethernet, token ring, X.25, Frame Relay
  and FDDI). Many routers can also function as
  bridges.

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Routers

• Repeaters and Bridges understand only Media
  Access Control (MAC) addresses
• Traffic flow between nodes entirely based on MAC
  addresses
• Packet from a host station ltmac-addr, payloadgt
• Routers understand IP addresses
• Special board that sits inside a bridge
• IP layer on all nodes send packets destined
  outside the LAN to the router
• Router sees a packet as ltip-hdr, payloadgt
• uses the ip-hdr to route the packet on to internet

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Question

• Learns the network topology and does not forward
  messages that don't need to be forwarded
• Repeater
• Bridge
• Switch
• Router

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Question

• Amplifies and reconditions signals to extend
  network segment
• Repeater
• Bridge
• Switch
• Router

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Question

• Allows multiple computers to communicate with one
  another at the same time
• Repeater
• Bridge
• Switch
• Router

Node
Node
?
Node
Node
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Question

• Smartest of the bunch (i.e understands ip
  addresses)
• Repeater
• Bridge
• Switch
• Router

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Project 5
Reminder!

• Due Friday, December 5th at
• 115959 pm EST
• HONEST!!!

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Questions?
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