Review Resource

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Review Resource

• OSI-TCP/IP-IP addressing and Network Technologies

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Table of Contents

• Enterprise
• Review the OSI Model
• Encapsulation
• LAN Devices Technologies
• Transport Layer
• IP Addressing

Go There!
Go There!
Go There!
Go There!
Go There!
Go There!
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A New Word!Enterprise

• A corporation, agency, school, or other
  organization that works to tie together its data,
  communication, computing, and file servers.

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Review The Model

• Open Systems Interconnected Reference Model

Table of Contents
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• Protocols
• Sets of rules or agreements that determine the
  format and transmission of data.
• These rules are what makes communication between
  different systems possible.

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Why A Layered Model?

• Reduces complexity
• Standardizes interfaces
• Facilitates modular engineering
• Ensures interoperable technology
• Accelerates evolution
• Simplifies teaching learning

Application
Presentation
Session
Transport
Network
Data-Link
Physical
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Host Layers vs. Media Layers
Host Layers Provides accurate data delivery
between computers
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Host Layers vs. Media Layers
Media Layers Controls physical delivery of the
message over the network
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Application Layer

• Provides network services (processes) to
  applications.
• For example, a computer on a LAN can save files
  to a server using a network redirector supplied
  by NOSs like Novell.
• Network redirectors allow applications like Word
  and Excel to see the network.

Application
Presentation
Session
Transport
Network
Data-Link
Physical
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Presentation Layer

• Provides data representation and code formatting.
• Code formatting includes compression and
  encryption
• Basically, the presentation layer is responsible
  for representing data so that the source and
  destination can communicate at the application
  layer.

Application
Presentation
Session
Transport
Network
Data-Link
Physical
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Session Layer

• Provides inter-host communication by
  establishing, maintaining, and terminating
  sessions.
• Session uses dialog control and dialog separation
  to manage the session
• Some Session protocols
• NFS (Network File System)
• SQL (Structured Query Language)
• RCP (Remote Call Procedure)
• ASP (AppleTalk Session Protocol)
• SCP (Session Control Protocol)
• X-window

Application
Presentation
Session
Transport
Network
Data-Link
Physical
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Transport Layer

• Provides reliability, flow control, and error
  correction through the use of TCP.
• TCP segments the data, adding a header with
  control information for sequencing and
  acknowledging packets received.
• The segment header also includes source and
  destination ports for upper-layer applications
• TCP is connection-oriented and uses windowing.
• UDP is connectionless. UDP does not acknowledge
  the receipt of packets.

Application
Presentation
Session
Transport
Network
Data-Link
Physical
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Network Layer

• Responsible for logically addressing the packet
  and path determination.
• Addressing is done through routed protocols such
  as IP, IPX, AppleTalk, and DECnet.
• Path Selection is done by using routing protocols
  such as RIP, IGRP, EIGRP, OSPF, and BGP.
• Routers operate at the Network Layer

Application
Presentation
Session
Transport
Network
Data-Link
Physical
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Data-Link Layer

• Provides access to the media
• Handles error notification, network topology
  issues, and physically addressing the frame.
• Media Access Control through either...
• Deterministictoken passing
• Non-deterministicbroadcast topology (collision
  domains)
• Important concept CSMA/CD

Application
Presentation
Session
Transport
Network
Data-Link
Physical
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Physical Layer

• Provides electrical, mechanical, procedural and
  functional means for activating and maintaining
  links between systems.
• Includes the medium through which bits flow.
  Media can be...
• CAT 5 cable
• Coaxial cable
• Fiber Optics cable
• The atmosphere

Application
Presentation
Session
Transport
Network
Data-Link
Physical
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• Layer PDUs
• 7 - Application ------------
• 6 - Presentation Data
• 5 - Session ------------
• 4 - Transport Segments
• 3 - Network Packets
• 2 - Data Link Frames
• 1 - Physical Bits

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• PDUs Layer
• Do Data 5-7
• Sergeants Segments 4
• Pay Packets 3
• For Frames 2
• Beer? Bits 1

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• TCP/IP Reference Model
• Layer 4 Application
• Layer 3 Transport
• Layer 2 Internet
• Layer 1 Network Access

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History and Future of TCP/IP

• The U.S. Department of Defense (DoD) created the
  TCP/IP reference model because it wanted a
  network that could survive any conditions.
• Some of the layers in the TCP/IP model have the
  same name as layers in the OSI model.

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Application Layer

• Handles high-level protocols, issues of
  representation, encoding, and dialog control.
• The TCP/IP protocol suite combines all
  application related issues into one layer and
  ensures this data is properly packaged before
  passing it on to the next layer.

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Application Layer Examples
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Transport Layer

• Five basic services
• Segmenting upper-layer application data
• Establishing end-to-end operations
• Sending segments from one end host to another end
  host
• Ensuring data reliability
• Providing flow control

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Transport Layer Protocols
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Internet Layer
The purpose of the Internet layer is to send
packets from a network node and have them arrive
at the destination node independent of the path
taken.
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Network Access Layer

• The network access layer is concerned with all of
  the issues that an IP packet requires to actually
  make a physical link to the network media.
• It includes the LAN and WAN technology details,
  and all the details contained in the OSI physical
  and data link layers.

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Comparing the OSI Model and TCP/IP Model
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Similarities of the OSI and TCP/IP Models

• Both have layers.
• Both have application layers, though they include
  very different services.
• Both have comparable transport and network
  layers.
• Packet-switched, not circuit-switched, technology
  is assumed.
• Networking professionals need to know both
  models.

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Differences of the OSI and TCP/IP Models

• TCP/IP combines the presentation and session
  layer into its application layer.
• TCP/IP combines the OSI data link and physical
  layers into one layer.
• TCP/IP appears simpler because it has fewer
  layers.
• TCP/IP transport layer using UDP does not always
  guarantee reliable delivery of packets as the
  transport layer in the OSI model does.

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Internet Architecture

• Two computers, anywhere in the world, following
  certain hardware, software, protocol
  specifications, can communicate, reliably even
  when not directly connected.
• LANs are no longer scalable beyond a certain
  number of stations or geographic separation.

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Encapsulation

• Peer-to-Peer Communications

Table of Contents
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• Encapsulation
• The process of wrapping the data being sent with
  the protocol information necessary to arrive at
  the packets destination.
• PDUs Protocol Data Units
• The information exchanged between peer layers in
  different systems.
• Within a system communication takes place
  vertically where the next lower layer provides
  support. Think vertical!
• With peer systems the communication occurs at the
  same layer. Think horizontal!

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Peer-to-Peer Communications

• Peers communicate using the PDU of their layer.
  For example, the network layers of the source and
  destination are peers and use packets to
  communicate with each other.

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Data Flow Through a Network
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Encapsulation Example

• You type an email message. SMTP takes the data
  and passes it to the Presentation Layer.
• Presentation codes the data as ASCII.
• Session establishes a connection with the
  destination for the purpose of transporting the
  data.

Application
Presentation
Session
Transport
Network
Data-Link
Physical
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Encapsulation Example

• Transport segments the data using TCP and hands
  it to the Network Layer for addressing
• Network addresses the packet using IP.
• Data-Link then encaps. the packet in a frame and
  addresses it for local delivery (MACs)
• The Physical layer sends the bits down the wire.

Application
Presentation
Session
Transport
Network
Data-Link
Physical
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LAN Devices Technologies

• The Data-Link Physical Layers

Table of Contents
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Devices

• What does it do?
• Connects LAN segments
• Filters traffic based on MAC addresses and
• Separates collision domains based upon MAC
  addresses.

What layer device?
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Devices

• What does it do?
• Since it is a multi-port bridge, it can also
• Connect LAN segments
• Filter traffic based on MAC addresses and
• Separate collision domains
• However, switches also offer full-duplex,
  dedicated bandwidth to segments or desktops.

What layer device?
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Devices

• What does it do?
• Concentrates LAN connections from multiple
  devices into one location
• Repeats the signal (a hub is a multi-port
  repeater)

What layer device?
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Devices

• What does it do?
• Interconnects networks and provides broadcast
  control
• Determines the path using a routing protocol or
  static route
• Re-encapsulates the packet in the appropriate
  frame format and switches it out the interface
• Uses logical addressing (i.e. IP addresses) to
  determine the path

What layer device?
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Media Types
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LAN Technologies
Three Most Common Used Today in Networking
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Ethernet and the OSI Model
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Ethernet and the OSI Model
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Ethernet and the OSI Model
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Layer 2 Framing
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Ethernet Frame Structures
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Ethernet Frame Structures
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Ethernet Frame Structures
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Ethernet Frame Fields
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Ethernet Frame Fields
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Ethernet/802.3

• Cable Specifications
• 10Base2
• Called Thinnet uses coax
• Max. distance 185 meters (almost 200)
• 10Base5
• Called Thicknet uses coax
• Max. distance 500 meters
• 10BaseT
• Uses Twisted-pair
• Max. distance 100 meters
• 10 means 10 Mbps

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Ethernet/802.3

• Ethernet is broadcast topology.
• What does that mean?
• Every devices on the Ethernet segment sees every
  frame.
• Frames are addressed with source and destination
  ______ addresses.
• When a source does not know the destination or
  wants to communicate with every device, it
  encapsulates the frame with a broadcast MAC
  address FFFF.FFFF.FFFF
• What is the main network traffic problem caused
  by Ethernet broadcast topologies?

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Ethernet/802.3

• Ethernet topologies are also shared media.
• That means media access is controlled on a first
  come, first serve basis.
• This results in collisions between the data of
  two simultaneously transmitting devices.
• Collisions are resolved using what method?

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Ethernet/802.3

• CSMA/CD (Carrier Sense Multiple Access with
  Collision Detection)
• Describe how CSMA/CD works
• A node needing to transmit listens for activity
  on the media. If there is none, it transmits.
• The node continue to listen. A collision is
  detected by a spike in voltage (a bit can only be
  a 0 or a 1--it cannot be a 2)
• The node generates a jam signal to tell all
  devices to stop transmitting for a random amount
  of time (back-off algorithm).
• When media is clear of any transmissions, the
  node can attempt to retransmit.

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Collisions in Collision Domain
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Layer 1 Devices Extend Collision Domains
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Broadcasts in a Bridged Environment
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Broadcast Domain Segmentation
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Obtaining an IP Address
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Obtaining an Internet Address

• Static addressing
• Each individual device must be configured with an
  IP address.
• Dynamic addressing
• Reverse Address Resolution Protocol (RARP)
• Bootstrap Protocol (BOOTP)
• Dynamic Host Configuration Protocol (DHCP)
• DHCP initialization sequence
• Function of the Address Resolution Protocol
• ARP operation within a subnet

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Static Assignment of IP Addresses

• Each individual device must be configured with an
  IP address.

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Reverse Address Resolution Protocol (RARP)
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BOOTP IP

• The Bootstrap Protocol (BOOTP) operates in a
  client/server environment and only requires a
  single packet exchange to obtain IP information.
• BOOTP packets can include the IP address, as well
  as the address of a router, the address of a
  server, and vendor-specific information.

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Dynamic Host Configuration Protocol

• Allows a host to obtain an IP address using a
  defined range of IP addresses on a DHCP server.
• As hosts come online, contact the DHCP server,
  and request an address.

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Address Resolution Protocol (ARP)

• Each device on a network maintains its own ARP
  table.
• A device that requires an IP and MAC address pair
  broadcasts an ARP request.
• If one of the local devices matches the IP
  address of the request, it sends back an ARP
  reply that contains its IP-MAC pair.
• If the request is for a different IP network, a
  router performs a proxy ARP.
• The router sends an ARP response with the MAC
  address of the interface on which the request was
  received, to the requesting host.

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Address Resolution Protocol

• In broadcast topologies, we need a way to resolve
  unknown destination MAC addresses.
• ARP is protocol where the sending device sends
  out a broadcast ARP request which says, Whats
  your MAC address?
• If the destination exists on the same LAN segment
  as the source, then the destination replies with
  its MAC address.
• However, if the destination and source are
  separated by a router, the router will not
  forward the broadcast (an important function of
  routers). Instead the router replies with its
  own MAC address.

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Problems in Address Resolution

• In TCP/IP communications, a datagram on a
  local-area network must contain both a
  destination MAC address and a destination IP
  address.
• There needs to be a way to automatically map IP
  to MAC addresses.
• The TCP/IP suite has a protocol, called Address
  Resolution Protocol (ARP), which can
  automatically obtain MAC addresses for local
  transmission.
• TCP/IP has a variation on ARP called Proxy ARP
  that will provide the MAC address of an
  intermediate device for transmission outside the
  LAN to another network segment.