Standards Organizations and The OSI Model

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Standards Organizations and The OSI Model
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Standards Organizations
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Standards Organizations

• IAB Internet Architecture Board
• IETF Internet Engineering Task Force
• IRTF Internet Research Task Force
• ISO International Organizations for
  Standardization
• ITU International Telecommunication Union
• ANSI American National Standards Institute
• IEEE Institute of Electrical and Electronics
  Engineers
• EIA Electronic Industries Association
• TIA Telecommunications Industry Association
• Vendor Forums
• ATM Asynchronous Transfer Mode
• Frame Relay

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IEEE and ANSI Standards

• IEEE and ANSI normally work on local and
  metropolitan area committees and subcommittees
• 802 (committee)
• 802.1 High-level interface
• 802.2 Logical link control sub-layer
• 802.3 CSMA/CD (Ethernet) networks
• 802.3u 100 Mbps Ethernet
• 802.3z Gigabit Ethernet
• 802.4 Token bus network
• 802.5 Token ring networks
• 802.6 Metropolitan area network
• 802.7 Broadband Technical Advisory Group
• 802.8 Fiber Optic Technical Advisory Group
• 820.9 Integrated Voice and Data LAN Working
  Group
• 802.10 LAN Security Working Group
• 802.11 Wireless Networking Working Group
• 802.12 Demand Priority Access Method
• 802.14 Cable modems
• ANSI -- X3 committee FDDI (Fiber Distributed
  Data Interface) standards

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OSI Model

• Open Systems Interconnection (OSI) model
• Created by the ISO as a basis for communication
  systems
• A 7-layer model, each layer works independently
  of one another
• Most implementations deviate from the rules set
  up by the OSI model
• Primarily used for educational and comparative
  purpose with respect to products and technologies
  commercially available
• A Pleasant Sales Transaction Never Delay Payment
  (Invent your own way to member the OSI model)

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OSI Model
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OSI Network Communication

• Each layer implements a specific communications
  function.
• Each layer is independent of all others
• A header, created by each layer, implements the
  function for that layer
• PDU (Protocol Data Unit) the combination of
  header and data
• The PDU created by one layer is passed as data to
  the PDU created by the next layer below

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OSI Network Communication
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Layer 1 Physical Layer

• Defines
• Cabling system components
• Category 5 UTP (unshielded twist pair for
  Ethernet)
• Fiber optic for backbone connections
• Connectors design and pin assignment
• RJ 45 for Ethernet
• Hub/repeater/concentrator
• Hubs devices used to connect multiple nodes
  together
• Patch panel help manage wiring
• Wireless components

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Layer 1 Physical Layer (example)
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Physical Layer Connectivity Devices

• Connectivity devices are used to connect devices
  on a LAN (Local Area Network)
• 10BaseT hub
• Token Ring MAU
• The hub samples the incoming bit stream and
  repeats a good signals to other devices connected
  to the hub
• Ethernet, Token Ring, and FDDI (Fiber Distributed
  Data Interface) hubs operate differently
• The hub does not look at data to see what the
  destination is

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Physical Layer Connectivity Devices
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Layer 2 Data Link Layer

• Builds and sends frames (containing the NOS
  information plus user data) out to a network
• Receives frames from a network
• Involves NICs (Network Interface Cards) and other
  devices
• MAC address
• Each device connected to a LAN must have a MAC
  (Media Access Control) address (also call NIC
  address)
• The address is typically 6 bytes long
• Example 02 60 8C 42 19 7A
• The NIC passes the frame to the physical layer,
  which transmit to the data to a physical link

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Layer 2 Data Link Layer
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Layer 2 Data Link Sub-Layers

• Data Link Layer has two sub-layers
• LLC (logical Link Control)
• Serves as an interface between a variety of media
  access control techniques and the upper-layer
  protocols
• Media Access Control sub-layer Uses information
  from the LLC sub-layer to provide
• Support to connection-oriented and connectionless
  service
• The address of the source service access point
  (SSAP)
• The address of the destination service access
  point (DSAP)

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Layer 2 Data Link Sub-Layers
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Layer 3 Network Layer

• Provides details so that data can be routed
  between devices in an environment with multiple
  networks.
• Use routers and the software used by the routers
• Information provided by the Network Layers
  includes
• Source and destination network addressing
• Subnet information
• Source and destination node address
• Source and destination ports used by the
  transport layer (layer 4)
• Based in the IP address
• Four decimal numbers separated by decimal points
• Each decimal number is one byte in length,
  ranging 0-255

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Layer 3 Network Layer
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A Quick Look at IP Address

• The IP address indicates to the router which user
  on which subnet at a specific organization

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Layer 4 Transport Layer

• To ensure transmitting integrity between two
  devices communicating through the network
• Data tracking
• Connection flow control
• Sequencing of data
• Error checking
• Application addressing and identification
• if data is lost or damaged, it is requested to be
  resent
• Each packet of data is assigned a unique sequence
  number and an associated acknowledgement number
  to track data

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Layer 4 Transport Layer
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Layer 4 Transport Layer

• Provides two types of services to an upper-layer
  protocol (the Connection layer)
• Connection-oriented Provide feedback about the
  data as it travels through network. Example TCP
  (transmission Control Protocol)
• A connection process (handshake) occurs before
  data transmission
• Requires some forms of acknowledgement
• Provides error detection and error recovery
  routines
• Provides a defined handshake drops down the
  connection
• Connectionless Provide no feedback from the
  receiver about the data/ Example UDP (User
  Datagram Protocol)
• Simply send data with a source and destination
  address appended
• No error recovery
• Used when efficiency is needed and cannot justify
  the extra overhead needed for error control

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Connection-Oriented Services
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Connectionless Services
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Layer 5 Session Layer

• Establishes, manages, and terminates connections
  between applications

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Layer 6 Presentation Layer

• Specifies how end-user applications should format
  the data
• Encryption and decryption of data
• Compression algorithms
• Character sets (ASCII and EBCIDIC)
• Formatting information

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Layer 6 Presentation Layer
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Layer 7 Application Layer

• Provides services for applications to access the
  network environment
• Examples
• FTP File transfer protocol
• SNMP Simple Network Management Protocol
• Telnet Virtual terminal protocol
• SMTP Simple Mail Transfer Protocol

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Layer 7 Application Layer
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TCP/IP Vs. OSI Model
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TCP/IP Vs. OSI Model

• Device B is transferring a file located in device
  A
• The application FTP is used
• FTP is a connection-oriented file transfer and
  uses TCP to track the transaction
• IP is used to find correct device on the network
• TCP/IP information and the file are delivered
  using an Ethernet Local Area Network