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Network Guide to Networks 5th Edition


Title: Network+ Guide to Networks 5th Edition Author: Sam Last modified by: Feda Created Date: 7/9/2007 9:56:01 PM Document presentation format: On-screen Show (4:3) – PowerPoint PPT presentation

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Title: Network Guide to Networks 5th Edition

Network Guide to Networks5th Edition
  • Chapter 2
  • Networking Standards and the OSI Model

  • Identify organizations that set standards for
  • Describe the purpose of the OSI model and each of
    its layers
  • Explain specific functions belonging to each OSI
    model layer

Objectives (contd.)
  • Understand how two network nodes communicate
    through the OSI model
  • Discuss the structure and purpose of data packets
    and frames
  • Describe the two types of addressing covered by
    the OSI model

Networking Standards Organizations
  • Standard
  • Documented agreement containing technical
    specifications/precise criteria
  • Stipulates design or performance of particular
    product or service
  • Used by industries to ensure that products,
    processes and services suit their purposes.
  • Standards are essential in the networking world
  • Wide variety of hardware and software
  • Ensures network design compatibility (ex. cable
    plug wall plate)
  • Standards define minimum acceptable performance
  • Not ideal performance

List of Standards Organizations
  • ANSI
  • ANSI (American National Standards Institute)
  • 1000 representatives from industry and
  • Determines standards for electronics industry and
    other fields(chemical nuclear engineering,
    health safety, etc.)
  • Represents US in setting international standards

List of Standards Organizations
  • EIA and TIA
  • EIA (Electronic Industries Alliance)
  • Trade organization
  • Representatives from United States electronics
    manufacturing firms
  • Sets standards for its members write ANSI

EIA and TIA (contd.)
  • TIA (Telecommunications Industry Association)
  • Formed in 1988
  • EIA subgroup merged with former United States
    Telecommunications Suppliers Association (USTSA)
  • Focus of TIA
  • Standards for information technology, wireless,
    satellite, fiber optics, and telephone equipment
  • TIA/EIA 568-B Series
  • Guidelines for installing network cable in
    commercial buildings

List of Standards Organizations
  • IEEE
  • IEEE (Institute of Electrical and Electronics
  • International engineering professionals society
  • Goal of IEEE
  • Promote development and education in electrical
    engineering and computer science fields
  • Hosts symposia, conferences, and chapter meetings
  • Maintains a standards board (establishes its own
    electronic and computer standard industries
    contributes to other standards bodies)

IEEE Student Chapter at CCSF
  • Last semester, the chapter arranged a tour of a
    data center
  • I'll let you know what's coming up this semester

List of Standards Organizations
  • ISO
  • ISO (International Organization for
  • ISO in Greek means equal
  • Headquartered in Geneva, Switzerland
  • Collection of standards organizations
  • Representing 157 countries
  • Goal of ISO
  • Establish international technological standards
    to facilitate global exchange of information and
    barrier free trade
  • Widespread authority textiles, packaging,
    banking, etc.

List of Standards Organizations
  • ITU
  • ITU (International Telecommunication Union)
  • Specialized United Nations agency that regulates
    international telecommunications including radio
    TV frequencies, satellite telephony
    specifications and networking infrastructure.
  • Provides developing countries with technical
    expertise and equipment
  • Founded in 1865 (Paris)
  • Joined United Nations in 1947
  • Members from 191 countries
  • Focus of ITU
  • Global telecommunications issues
  • Worldwide Internet services implementation

List of Standards Organizations
  • ISOC
  • ISOC (Internet Society)
  • Founded in 1992
  • Professional membership society
  • Establishes technical Internet standards
  • Current ISOC concerns
  • Rapid Internet growth
  • Keeping Internet accessible
  • Information security
  • Stable Internet addressing services
  • Open standards

ISOC (contd.)
  • ISOC oversees groups with specific missions
  • IAB (Internet Architecture Board)
  • Technical advisory group
  • Overseeing Internets design and management
  • IETF (Internet Engineering Task Force)
  • Sets Internet system communication standards
  • Particularly protocol operation and interaction
  • Anyone may submit standard proposal
  • Elaborate review, testing, and approval processes

List of Standards Organizations
  • IANA and ICANN
  • IP (Internet Protocol) address
  • Address identifying computers in TCP/IP based
    (Internet) networks
  • Reliance on centralized management authorities
  • IP address management history
  • Initially IANA (Internet Assigned Numbers
  • 1997 Three RIRs (Regional Internet Registries)
  • ARIN (American Registry for Internet Numbers)
  • APNIC (Asia Pacific Network Information Centre)
  • RIPE (Réseaux IP Européens)

IANA and ICANN (contd.)
  • IP address management history (contd.)
  • Late 1990s ICANN (Internet Corporation for
    Assigned Names and Numbers)
  • Private nonprofit corporation
  • Remains responsible for IP addressing and domain
    name management
  • IANA performs system administration
  • Users and business obtain IP addresses from ISP
    (Internet service provider)

ICANN's Stormy History
  • 2002 ICANN was sued by one of their own board
    members to force them to disclose financial
  • 2003 ICANN sued Verisign to make them shut down
    their "Site Finder" service, which captured all
    mistyped URLs and showed them Verisign ads
  • 2004 Verisign sued ICANN saying they had
    overstepped their authority
  • 2008 Ten worst spam offenders notified by ICANN
  • Links Ch 2a, 2b, 2c

The OSI Model
  • Open System Interconnection model
  • Model for representing theoretically the
    communication between two nodes on a network
    regardless of their underlying software or
  • Developed by ISO (1980s)
  • Divides network communications into seven layers
  • Physical, Data Link, Network, Transport, Session,
    Presentation, Application

The OSI Model (contd.)
  • Protocols
  • Rules by which computers communicate
  • A set of instructions written by a programmer to
    perform a function or a set of functions
  • Some are included with a computers OS and others
    are files installed with SW programs.
  • Performs services unique to the layer
  • Interact with protocols in the above/below layers
  • Application layer protocols
  • Interact with software
  • Email, spreadsheet, etc.

The OSI Model (contd.)
  • Physical layer protocols
  • Act on cables and connectors
  • To issue and receive signals
  • Logically each layer communicates with its peer
    corresponding layer in the second node
  • The communication process starts at layer 7
    (application) and initiated by a user or device
    to start data exchange, the application layer
    separates data into PDU. Then, PDU progress down
    through OSI model layers (6,5,4,3,2,1) and
    header is added to the data unit except layer 7.
    After that data traverses network until it
    reaches second nodes physical layer and data
    progress up the OSI(ms)

The OSI Model (contd.)
  • Every network communication process represented
  • PDUs (protocol data units)
  • Discrete amount of data
  • Application layer function
  • Flow through layers 6, 5, 4, 3, 2, and 1
  • Generalized model and sometime imperfect

Figure 2.1 Flow of data through the OSI model
Mnemonics for the OSI Model
  • Bottom Up
  • Please (Programmers)
  • Do
  • Not
  • Throw
  • Sausage (Salty)
  • Pizza (Pretzels)
  • Away
  • Top Down
  • All
  • People
  • Seem
  • To
  • Need
  • Data
  • Processing

Application Layer
  • Top (seventh) OSI model layer
  • No software applications (MS word, Firefox, etc.)
  • Separate data into PDU
  • Protocol functions (services)
  • Facilitates communication
  • Between software applications and lower-layer
    network services
  • Network can interpret application request
  • Application can interpret data sent from network
  • Format, security, synchronization and other
    network requirements negotiation between SW
    programs networks (ex Library Web page HTTP)

Presentation Layer
  • Allows hosts and applications to use a common
  • Protocol functions
  • Serves as translator
  • Accept Application layer data
  • Formats data to make it understandable to
    different applications and hosts
  • Examples
  • Text encoding methods ASCII and EBCDIC
  • Compression methods like GIF, JPEG and TIFF for
    images and MPEG and Quicktime for audio video.
  • Data encryption and decryption (ex. Bank account)

Session Layer
  • Protocol functions
  • Establishes, coordinates, maintains and
    terminates communications between two nodes
  • Session
  • Connection for ongoing data exchange between two
  • Historically used for terminals mainframes
  • Now Web browser server remote client access
  • Functions
  • Establishing and keeping alive communications
  • Securing the communication ensuring
  • Synchronize dialogue between nodes
  • Determining if communications ended
  • Determining where to restart transmission, which
    node communicate first, duration of communication
  • Terminating communications

Transport Layer
  • Protocol functions
  • Accept data from Session layer
  • Manage end-to-end data delivery (reliably, no
    errors, correct sequence)
  • Handles flow control
  • Process of gauging the appropriate rate of
    transmission based on the recipient (how fast it
    can accept data)
  • Provides reassembly
  • Process of reconstructing segmented data units
  • Provides sequencing
  • Method of identifying segments belonging to the
    same group of subdivided data, it indicates start
    of unit data, order of groups of data

Transport Layer (contd.)
  • Provides segmentation, and error control
  • Process of breaking large data units received
    from the session layer into multiple smaller
    units called segments
  • Increase transmission efficiency
  • Match a network MTU
  • Maximum Transmission Unit
  • Largest data unit carried by the network
  • Ethernet default 1500 bytes
  • Discovery routine used to determine MTU
  • Run discovery routine upon establishing a
    connection with the network to learn the MTU size

Transport Layer
  • Types of Transport Layer Protocols TCP and UDP
  • TCP
  • Connection-oriented
  • Establishes a connection before transmitting data
  • Three-way handshake

Transport Layer
  • TCP
  • Require acknowledgements from receiver to ensure
    data was received correctly (reliable
  • Checksum
  • Process that uses a unique character string
    allowing receiving node to determine if arriving
    data unit exactly matches data unit sent by
  • Ensures data integrity

Send data, wait for ACK
Send more data, wait for ACK
Transport Layer
  • UDP
  • Connectionless protocol
  • Do not establish connection with another node
    before transmitting datano handshake
  • Make no effort to ensure data is reliable ( no
  • Faster than connection-oriented protocol
  • Useful when data must be transferred quickly,
    such as streaming music or video

Transport Layer (contd.)
Figure 2-2 Segmentation and reassembly
Network Layer
  • Establishes network connections, translates
    network address to physical address and
    determines routing
  • Addressing
  • System for assigning unique identification
    numbers to devices on a network
  • Two types of addressing
  • Network/logical/virtual address
  • Hierarchal scheme (subset of data that
    incrementally narrow down the location of a node)
  • Depends on network protocol
  • Physical/MAC/datalink/hardware address
  • Unique
  • 0060973E97F3 (12 hex digits)

Network Layer
  • Protocol Functions
  • Address translation (network Physical)
  • Packet formation
  • Process of adding logical addressing
    informationIP address to transport layer segment
    to produce network layer packet
  • Routing
  • Process of determining the best path from point A
    on one network to point B on another network
  • Intelligently direct data based on addressing,
    patterns of usage and availability
  • Routing considerations
  • -Delivery priorities -Network congestion
  • -Quality of service -Cost of alternative

Network Layer
  • Fragmentation
  • Network layer protocol (IP) subdivides Transport
    layer segments received into smaller packets?
    ensures that packets are not larger than the
    networks maximum transmission unit size
  • This is usually avoided by adjusting the Maximum
    Segment Size in the Transport layer, because it
    makes data transfer inefficient
  • Router device that connects network segments
    and directs data
  • Common Network layer protocol
  • IP (Internet Protocol)
  • Protocol that instructs the network where the
    HTTP request is coming from where it is going
    to (src dst)

Data Link Layer
  • Function of protocols
  • Divide data received into distinct frames for
    transmission in Physical layer
  • Add Physical address to the frame MAC addresses
    like 00-30-48-82-11-BD
  • Frame
  • Structured package for moving data
  • Includes raw data (payload), senders and
    receivers physical addresses, error checking and
    control information

Data Link Layer (contd.)
  • Frames may be damaged as they pass through the
    Physical layer, so the Data Link layer has
  • Error checking
  • Frame check sequence
  • CRC (cyclic redundancy check)
  • Possible glut of communication requests
  • Data Link layer controls flow of information
  • Allows NIC to process data without error

Data Link Layer (contd.)
  • Two Data Link layer sublayers
  • LLC (Logical Link Control) sublayer
  • MAC (Media Access Control) sublayer
  • MAC address components
  • Block ID
  • Six-character sequence unique to each vendor
  • Device ID
  • Six-character number added at vendors factory
  • MAC addresses frequently depicted in hexadecimal

Example of MAC Address
  • Whole MAC address 00-30-48-82-11-BD
  • Block ID
  • 00-30-48
  • Identifies the vendor
  • Device ID
  • 82-11-BD
  • Different for each NIC from the same vendor
  • If two NICs have the same MAC address, they have
    problems networking
  • This can happen with cheaply made refurbished
    NICs, or with copied virtual machines

Data Link Layer (contd.)
Figure 2-5 The Data Link layer and its sublayers
Data Link Layer (contd.)
Figure 2-6 A NICs Mac address
Finding Your MAC Address
  • Start, CMD, Enter
  • Scroll up to see the first entry

MAC Address (also called "Physical Address")
IP Address
Physical Layer
  • Functions of protocols
  • Accept frames from Data Link layer
  • Generate signals as changes in voltage at the NIC
  • Copper transmission medium
  • Signals issued as voltage
  • Fiber-optic cable transmission medium
  • Signals issued as light pulses
  • Wireless transmission medium
  • Signals issued as electromagnetic waves

Physical Layer (contd.)
  • Physical layer protocols responsibility when
    receiving data
  • Detect and accept signals
  • Pass on to Data Link layer
  • Set data transmission rate
  • Monitor data error rates
  • No error checking
  • Devices operating at Physical layer
  • Hubs and repeaters
  • NICs operate at both Physical layer and Data Link

Applying the OSI Model
Communication Between Two Systems
  • Data transformation
  • Original software application data differs from
    the bits sent onto the cable by the NIC
  • Header data added at each layer (ex. Format
    specification, network address,) except layer
    7and trailer is added at data link layer
  • Each layer has a different data structure, called
    a Protocol Data Unit (PDU)
  • Segments
  • Generated in Transport layer
  • Unit of data resulting from subdividing larger
    PDU from the Session layer
  • Addressed with TCP Ports (when using TCP)

Communication Between Two Systems (contd.)
  • Packets
  • Generated in Network layer
  • Data with logical addressing information added to
  • Addressed with IP addresses
  • Frames
  • Generated in Data Link layer
  • Composed of several smaller components or fields
  • Addressed with MAC addresses

Communication Between Two Systems (contd.)
  • Encapsulation
  • Occurs in each layer
  • Process of wrapping one layers PDU with protocol
  • Allows interpretation by lower layer

Communication Between Two Systems (contd.)
Communication Between Two Systems (contd.)
  • Example get mail message from remote mail server
  • Communication Steps for Server/Client exchange
  • Application Layer accepts data, formulates
    request and adds an application header ?transfer
    PDU to presentation layer.
  • Presentation Layer determines whether how it
    format and encrypt the data request received and
    adds presentation header ? transfer PDU to
    session layer
  • Session Layer adds session header ( transmission
    rate, how to communicate with network) ? transfer
    PDU to transport layer.

Communication Between Two Systems (contd.)
  • Transport Layer segments the PDU (max. size of
    segment is dictated by the type of network
    transmission method for example Ethernet) and
    adds transport header ( sequence identifier,
    checksum, flow control and acknowledgment) ?
    transfer PDU (segments) to network layer.
  • Network Layer adds network header that contains
    the logical address of the destination ? transfer
    PDU (packet) to data link layer.
  • Data Link Layer adds data link header for
    checking errors and trailer for indicating end of
    packet ? transfer PDU (frame) to physical layer.

Communication Between Two Systems (contd.)
  • Physical Layer Does not interpret or add any
    information to the frame but transmits them over
    the broadband connection across the network after
    converting binary digits into pulses.
  • The frames arrive at the mail server and accepted
    by its physical layer and reverse the process
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