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Chapter2

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  • This chapter describes the fundamentals of communication and how they apply to communication in and between data networks. Two important models that describe the process of network communication and the devices will be used to illustrate communication between network hosts.
  • The downside to using segmentation and multiplexing to transmit messages across the network is the level of complexity that is added to the process.
  • Processes running on the intermediary network devices perform these functions: Regenerate and retransmit data signals Maintain information about what pathways exist through the network and internetwork Notify other devices of errors and communication failures Direct data along alternate pathways when there is a link failure Classify and direct messages according to QoS priorities Permit or deny the flow of data, based on security settings
  • The slide shows the processes running on the intermediary network devices.
  • Light is kept in the  core  of the optical fiber by  total internal reflection . 
  • One of the best ways to visualize how all of the protocols interact on a particular host is to view it as a stack. A protocol stack shows how the individual protocols within the suite are implemented on the host. The protocols are viewed as a layered hierarchy, with each higher level service depending on the functionality defined by the protocols shown in the lower levels. The lower layers of the stack are concerned with moving data over the network and providing services to the upper layers, which are focused on the content of the message being sent and the user interface.
  • In data communications, for example, if one end of a conversation is using a protocol to govern one-way communication and the other end is assuming a protocol describing two-way communication, in all probability, no information will be exchanged.
  • An example of the use of a protocol suite in network communications is the interaction between a web server and a web browser. This interaction uses a number of protocols and standards in the process of exchanging information between them. The different protocols work together to ensure that the messages are received and understood by both parties.
  • There are benefits to using a layered model to describe network protocols and operations.
  • Make a Comparison between the 2 models
  • The above seven steps in the communication process are indicated in the next slide.
  • This slide shows the seven steps in the communication process.
  • In the web server example, the TCP/IP model is used to illustrate the process of sending an HTML web page to a client.
  • This process is reversed at the receiving host. The data is decapsulated as it moves up the stack toward the end user application.

Chapter2 Chapter2 Presentation Transcript

  • Ch 2 - Chapter 2 Communicating over the Network Network Fundamentals
  • Objectives
    • Describe the structure of a network, including the devices and media that are necessary for successful communications
    • Explain the function of protocols in network communications
    • Explain the advantages of using a layered model to describe network functionality
    • Describe the role of each layer in two layered models: the TCP/IP model and OSI model
    • Describe the importance of addressing and naming schemes in network communications
    Ch 2 -
  • Elements of Communication
    • Message source or sender
      • people or electronic devices that send a message to other individuals or devices
    • Destination or receiver of the message
      • the message is received and interpreted
    • Channel
      • consists of the media that provides the pathway over which the message can travel from source to destination
    Ch 2 -
  • Communicating the Message
    • Segmentation
      • divide the data into smaller, more manageable pieces called segments
      • many different conversations can be interleaved on the network, giving each user a part of the bandwidth – multiplexing
      • increases the reliability of network communications
    Ch 2 -
  • Addressing and Labeling the Segments
    • Segmenting and multiplexing a message requires additional processes
      • addressing and labeling each segment at the source
      • reassembling the segments into its original message at the destination
    Ch 2 -
  • Components of the Network
    • Networks use devices, media and services
    • Hardware or physical elements
      • devices and media
    • Software that run on the networked devices
      • services such as applications and processes that provide the functionality to direct and move the messages through the network
    Ch 2 -
  • End Devices
    • An end device refers to a piece of equipment that is either the source or the destination of a message on a network
      • the interface between the human and the network
      • also known as a host
      • each host is identified by an address
    Ch 2 -
  • Intermediary Devices
    • Provide connectivity and ensures data flows across the network
    • Connect individual hosts to the network and can connect multiple individual networks to form an internetwork
    • Use the destination host address to determine the path the messages take through the network
    Ch 2 -
  • Intermediary Device Processes
    • Regenerate and retransmit data signals
    • Maintain information about what pathways or routes exist through the network and the internetwork
    • Notify other devices of errors and communication failures
    • Direct data along alternate routes when there is a link failure
    • Classify and direct messages according to QoS priorities
    • Permit or deny the flow of data based on security settings
    Ch 2 -
  • Network Media
    • Modern networks primarily use three types of media
      • copper wires within cables
      • glass or plastic fibers ( fiber optic cable)
      • wireless transmission
    • The signal encoding method is different for each media type
      • data is encoded into electrical pulses on copper wires
      • fiber optic transmissions rely on pulses of light, within either infrared or visible light ranges
      • patterns of electromagnetic waves represent the various bit values in wireless transmission
    Ch 2 -
  • Examples of Network Media Ch 2 -
  • Selecting a Network Media
    • The distance the media can successfully carry a signal
    • The environment in which the media is installed
    • The amount of data and the speed at which it must be transmitted
    • The cost of the media and installation
    Ch 2 -
  • Network Infrastructures
    • Network infrastructures can vary in terms of:
      • the size of the area covered
      • the number of users connected
      • the number and type of services available
    • Common types of network infrastructures
      • local area networks (LANs)
      • wide area networks (WANs)
      • Internet
    Ch 2 -
  • Local Area Networks (LANs)
    • A LAN usually spans a small geographical area
      • provides services and applications to people within a common organizational structure, such as a home, building or campus
      • usually administered by a single organization
      • security and access control policies are enforced on the network level
    Ch 2 -
  • Wide Area Networks (WANs)
    • Telecommunications service provider (TSP) networks are used to interconnect an organization’s LANs that are located geographically far apart
      • TSPs operate large regional networks that span long distances
      • the TSP networks are referred to as wide area networks (WANs)
    • WANs use specifically designed network devices to make the interconnections between LANs
    Ch 2 -
  • The Internet – A Network of Networks
    • A need to communicate with a resource on another network
      • sending an e-mail to a friend in another country
      • accessing news or products on a website
      • instant messaging with someone in another city
    • Internetwork
      • a global mesh of interconnected networks
      • owned by large public and private organizations
      • the Internet is an example of a publicly-accessible internetwork
    • Intranet
      • private connection of LANs and WANs that belongs to an organization
      • accessible only by the organization’s members, employees, or others with authorization
    Ch 2 -
  • The Internet
    • LANs and WANs may be connected into internetworks
    Ch 2 -
  • Protocols
    • Pre-determined rules that govern communications
    • A group of inter-related protocols that are necessary to perform a communication function is called a protocol suite
    Ch 2 -
  • What is the Role of Protocols?
    • The format or structure of the message, such as how much data to put into each segment
    • The process by which intermediary devices share information about the path to the destination
    • The method to handle error and system messages between intermediary devices
    • The process to setup and terminate communications or data transfers between hosts
    Ch 2 -
  • Role of Protocols: Format
    • The format or structure of the message
      • defines the size of each protocol data unit (PDU)
    Ch 2 -
  • Role of Protocols: Process
    • The process by which intermediary devices share information about the path to the destination
    Ch 2 -
  • Role of Protocols: Error Messages
    • The method to handle error and system messages between intermediary devices
    Ch 2 -
  • Role of Protocols: Termination
    • The process to setup and terminate communications or data transfers between hosts
      • define the duration of inactivity or idle timeout to terminate a connection
    Ch 2 -
  • Protocol Suites and Industry Standards
    • A standard is a process that has been endorsed by the networking industry and officially approved by a standards organization
    • The use of standards in developing and implementing protocols ensures that products from different manufacturers can work together for efficient communications
    Ch 2 -
  • Interaction of Protocols
    • Application Protocol
      • HTTP defines the content and formatting of the requests and responses exchanged between the client and the server
    • Transport Protocol
      • TCP manages the individual conversations and divides the HTTP messages into smaller pieces called segments
      • TCP is also responsible for controlling the size and rate at which messages are exchanged
    Ch 2 -
  • Interaction of Protocols (cont’d)
    • Internetwork Protocol
      • IP is responsible for taking the formatted segments from TCP, encapsulating them into packets , assigning the appropriate IP addresses, and selecting the best path to the destination
    • Network Access Protocols
      • describes the data link management and the physical transmission of the data on the media
      • data-link management protocols encapsulates the packets into frames
      • the physical media standards and protocols govern how the signals are sent over the media and how they are interpreted by the receiving end device
    Ch 2 -
  • Technology-Independent Protocols
    • The implementation of a particular protocol is technology independent
      • protocols describe what functions are required
      • protocols do not describe how to accomplish a particular function
    Ch 2 -
  • What is Benefits of a Layered Model?
    • Assists in protocol design
      • protocols that operate at a specific layer have defined information that they act upon and a defined interface to the layers above and below
    • Fosters competition
      • products from different vendors can work together
    • Prevents technology or capabilities changes in one layer from affecting other layer above and below
    • Provides a common language to describe networking functions and capabilities
    Ch 2 -
  • Protocol and Reference Models
    • A protocol model provides a model that closely matches the structure of a particular protocol suite
      • Transmission Control Protocol/Internet Protocol (TCP/IP)
    • A reference model provides a common reference for maintaining consistency within all types of network protocols and services
      • it is not intended to be an implementation specification or to provide a sufficient level of detail to define precisely the services of the network architecture
      • the primary purpose is to aid in clearer understanding of the functions and processes involved
      • Open Systems Interconnection (OSI) model
    Ch 2 -
  • TCP/IP and OSI Models
    • The TCP/IP model describes the functions that occur at layer of protocols within the TCP/IP suite ( NITA )
    • The OSI model is used for network design, operation specifications and troubleshooting ( P ls D o N ot T hrow S ausage P izza A way)
    Ch 2 -
  • TCP/IP Model
    • Defines four communication functions that protocols perform
    • An open standard developed in the early 1970s
      • the definitions of the standards and the protocols are defined in publicly-available documents called Request For Comments (RFCs)
    Ch 2 -
  • Communication Process
    • Creation of data at the application layer of the originating source end device
    • Segmentation and encapsulation of data as it passes down the protocol stack in the source end device
    • Generation of the data onto the media at the network access layer of the stack
    • Transportation of the data through the internetwork, which consists of media and any intermediary devices
    • Reception of the data at the network access layer of the destination end device
    • Decapsulation and reassembly of the data as it passes up the stack in the destination device
    • Passing this data to the destination application at the application layer of the destination end device
    Ch 2 -
  • Communication Process (cont’d) Ch 2 - 1 2 3 4 5 6 7 source destination
  • Protocol Data Unit and Encapsulation
    • Protocol data unit (PDU) is the generic term for “data” at each level
    • Encapsulation is the process of adding control information as it passes through the layered model
    Ch 2 -
  • Sending Process
    • The Application layer begins the process by delivering the data to the Transport layer
    • The Application data is broken into TCP segments and each segment is given a label, called a header
      • the header contains information about which process running on the destination computer should receive the message
      • it also contains the information to enable the destination process to reassemble the segments
    • The TCP segment is sent to the Internet layer and encapsulated within an IP packet , which adds an IP header
      • the IP header contains the source and destination IP addresses
    Ch 2 -
  • Sending Process (cont’d)
    • The IP packet is sent to the Network Access layer where it is encapsulated with a frame header and trailer
      • each frame header contains the source and destination physical addresses
      • the trailer contains error checking information
    • Finally the bits are encoded onto the Ethernet media by the end-device network interface card (NIC)
    Ch 2 -
  • Sending Process (cont’d) Ch 2 -
  • Receiving Process Ch 2 -
  • Comparing the OSI and TCP/IP Models
    • The functions of the Application, Presentation and Session layers of the OSI model are combined into one Application layer in the TCP/IP model
    • The Data Link and Physical layers of the OSI model combine to make the Network Access layer of the TCP/IP model
    Ch 2 -
    • The key parallel between the two models occur at layers 3 and 4 of the OSI model
      • TCP operates at the transport layer
      • IP operates at the Internet layer
  • *Addressing
    • Various types of addresses are needed to successfully deliver the data from a source application running on one host to the correct destination application running on another
      • Data Link physical addresses
      • Network logical addresses
      • Transport service port numbers
    Ch 2 -
  • Layer 2 Address(Datalink)
    • This is the physical address of the host (or end device)
      • in a LAN using Ethernet, this address is called the Media Access Control (MAC ) address
    • Layer 2 addresses are used to communicate between devices on a single local network
    Ch 2 - (packet)
  • Layer 3 Address(Network)
    • This is the logical address ( IP address )
    • Layer 3 addresses are primarily used to move data from one local network to another local network
      • enable intermediary network devices to locate hosts on different networks
    Ch 2 - (segment) Network 209.165.200 Device 230
  • Layer 4 Service Port Number(Transport)
    • At layer 4, the information contained in the PDU header identifies the specific process or service running on the destination host device
      • the separately running programs are examples of individual processes
    Ch 2 -