Communicating Over the Network – Data Communication and Networking

Posted by djaney on November 20, 2009 · Leave a Comment 


From: John D. Tajones

 

  • Elements of Communication
  • Communication usually starts with a message.
    • Message source/Sender
      • E.g; people or electronic devices
    • Destination or receiver.
      • Receives and interprets message
    • Channel
      • Consist of the media that provides the pathway over which the message can travel from source to destination.
      • E.g; coaxial cable, Fiber Optic, microwave, UTP cable
  • Elements of Communication
  • Communicating Messages
  • Theoretically, a single communication such as an e-mail, could be sent across a network from a source to a destination as one massive continuous stream of bits.
  • Segmentation
    • Dividing the data into smaller, more manageable pieces to send over the network.
    • Benefits of Segmentation
      • Interleaved the pieces of separate conversation together on the network. (Multiplexing)
      • Increase the reliability of network communications.

       

       

  • Communicating Messages
  • Communicating Messages
  • Various types of devices throughout the network participate in ensuring that the pieces of the message arrive reliably at their destination.
  • Components of a Network

 

  • Devices
    • End devices such as PC, Laptop
  • Media
    • It is where communication travels
    • E.g. Fiber Optic, Coaxial cable
  • Services
    • Communication program called software, that run on the networked devices.
  • Components of a Network
  • End Devices and their Role in the Network
  • End devices
    • A device such as a desktop or mobile device that is used by an end user.
    • E.g; Computers (works stations, laptops, file servers, web server), Network printers, VoIP Phones, Security cameras, Mobile handheld devices (wireless barcode scanners, PDAs)
  • In network context, end devices are referred to as host. A host device is either the source or destination of a message transmitted over the network.

     

  • End Devices and their Role in the Network
  • Hosts can act as a client, a server, or both.
    • Server are hosts that have software installed that enable them to provide information and services, like e-mail or web pages, to other hosts on the network.
    • Clients are hosts that have software installed that enables them to request and display the information obtained from the server.

     

  • Intermediary Devices

 

  • Intermediary devices connects directly to end user devices or provides end user routing to other networks.
  • Examples
    • Network Access Devices (Hubs, switches, and wireless access points)
    • Internetworking Devices (routers)
    • Communication Servers and Modem
    • Security Devices (firewall)
  • Intermediary Devices
  • Intermediary Devices Functions:
    • Regenerate and retransmit data signals
    • Maintain pathway information existing in the network.
    • Notify other devices of errors and communication failures.
    • Direct data to alternate pathway during a link failure.
    • Classify and direct messages according to QoS priorities
    • Permit or deny the flow of data, based on security settings.
  • Network Media
  • Network media provides the channel over which the message travels from source to destination.
  • Types of Media
    • Metallic wires within cable
    • Glass or plastic fibers (fiber optic cable)
    • Wireless transmission
  • Each type has different way of encoding signals
  • Encoding is the process of transforming data from one form to another form. E.g; metallic wires for electrical impulses, FO for pulses of light, wireless transmission relied on electronic waves

 

  • Network Media
  • Network Media

 

  • Different types of media has different features and benefits.
  • Criteria in Choosing Network Media:
    • The distance the media can successfully carry a signal.
    • The environment in which the media is to be installed.
    • The amount of data and the speed at which it must be transmitted.
    • The cost of the media and installation.

     

  • The Platform for Communications

 

  • Networks infrastructures can vary in terms of:
    • The size of the area covered
    • The number of users connected
    • The number and types of services available
      • Local Area Network
      • WANs
      • Internetwork

 

  • Local Area Networks
  • Local Area Networks

 

  • Local Area Networks refers to a local network, or a group of interconnected local networks that are under the same administrative control.
  • The administrative control that governs the security and access control policies are enforced on the network level.

 

  • Wide Area Network (WAN)
  • Wide Area Networks (WANs)

 

  • WANs interconnected LANs which are being separated to different geographical area.
  • WANs uses a telecommunication service provider (TSP) to transport voices and data communications on separate networks.
  • The Internet – Network of Networks
  • The Internet – Network of Networks
  • Internet help us to communicate with a resource to another network, outside of our local organization.
  • Example of this type of communication include:
    • Sending an e-mail
    • Accessing news or products on a website
    • Getting a file from a neighbor’s computer
    • Instant messaging with a relative in another city
  • Internetwork is a global mesh of interconnected networks. Most well-known and widely used publicly-accessile internetworks is the internet.
  • The Internet – Network of Networks
  • Internet is created by the interconnection of networks belonging to Internet Service Provider. These ISP’s networks connect to each other to provide access for millions of users all over the world.
  • Intranet is often used to refer to a private of LANs and WANs that belongs to an organization, and is designed to be accessible only by the organization’s members, employees or others with authorization.
  • Network Representations
  • The language of networking uses a common set of symbols to represent the different end devices, network devices and media
  • Addition Network Representation Terms
    • Network Interface Card (NIC) or LAN Adapter – provides the physical connections to the network at the PC or other host device.
    • Physical Port – a connector or outlet on a networking device where the media is connected to a host or other networking device.
    • Interface – specialized ports on an internetworking device that connects to individual networks.
  • Network Representations
  • The language of networking uses a common set of symbols to represent the different end devices, network devices and media
  • Addition Network Representation Terms
    • Network Interface Card (NIC) or LAN Adapter – provides the physical connections to the network at the PC or other host device.
    • Physical Port – a connector or outlet on a networking device where the media is connected to a host or other networking device.
    • Interface – specialized ports on an internetworking device that connects to individual networks.
  • Network Representations
  • Rules that Govern Communications

 

  • Protocol Suite is a group of inter-related protocols that are necessary to perform a communication function.
  • Best ways to visualize how all of the protocols interact on a particular host is to view it as a stack.
  • Protocol usually viewed as a layered hierarchy, with each higher level service depending on the functionality defined by the protocols shown in the lower levels.
  • Rules that Govern Communications
  • Network Protocols
  • Protocols Provide the following
    • The format or structure of the message
  • Network Protocols
    • The process by which networking devices share information about pathways to other networks.

     

  • Network Protocols
    • How and when error and system messages are passed between devices.

     

  • Network Protocols
    • The setup and termination of data transfer sessions.

     

  • Interaction Protocol Example
  • Web server and Web browser interaction
  • Interaction Protocol Example
  • Protocols include:
    • Application Protocol
      • HTTP – is a common protocol that governs the way that a web server and a web client interact.
    • Transport Protocol
      • Transport Control Protocol (TCP) is the transport protocol that manages the individual conversations between web server and web clients.
      • TCP divides HTTP messages into smaller pieces, called segments, to be sent to the destination client.
      • TCP is also responsible for controlling the size ad rate at which message are exchange.

     

  • Interaction Protocol Example
  • Protocols include:
    • Internetwork protocol
      • Internet Protocol (IP) is the most common internetwork protocol.
      • IP responsible for taking the formatted segments from TCP, encapsulating them into packets, assigning the appropriate addresses, and selecting the best path to the destination host.
    • Network Access Protocol
      • Two Primary Functions
        • Data Link Management – format packets from IP that to be transmitted over the media.
        • Physical Transmission – govern how the signals are sent over media and how it being interpreted by receiving client. (E.g., NIC)
  • The Benefits of Layered Model
  • The Benefits of Layered Model

 

  • Assist in protocol design
  • Fosters competition
  • Prevents technology or capability changes in one layer from affecting other layer.
  • Provides a common language to describe networking functions and capabilities.
  • Types of Networking Models
  • Protocol models
    • Typically represents all the functionality required to interface the human network with data network.
    • TCP/IP model is protocol model which occurs at each layer.
  • Reference models
    • A common reference for maintaining consistency within all types of network protocols and services.
    • Primary purpose is to aid in clearer understanding of the functions and process involved.
    • Open System Interconnection (OSI) is most widely known reference model, which used for data networking design, operation specifications and troubleshooting.
  • Types of Networking Models
  • The TCP/IP Model
  • The TCP/IP Model
  • TCP/IP describes the functionality of the protocols that make up the TCP/IP protocol suite.
  • The communication process over this protocol:
    • Creation of data at the application layer from source
    • Segmentation 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 consist of media and any intermediary devices
    • Reception of the data at the network access layer of the destination end device.
    • Decapsulate 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.

     

  • The TCP/IP Model
  • Protocol Data Units and Encapsulation
  • Encapsulation is a process in which as data process each layer, various information will be added to the data.
  • PDU (Protocol Data Unit) used to described data as it moves from one layer to another.
  • PDU at each layer:
    • Data
      • general term for PDU used at the application layer
      • Data that will be send over network
    • Segment
      • Transport layer PDU
    • Packet – internetwork layer PDU
    • Frame – Network Access layer PDU
    • Bits – a PDU used when physically transmitting data over the medium

     

  • Protocol Data Units and Encapsulation
  • The Sending and Receiving Process
  • The Sending and Receiving Process
  • HTTP delivers data to Transport Layer
  • Transport Layer
    • Broke down data into segments
    • Attach transport header to each which contains which process will receive the message and enable the receiving process to reassemble segment.
  • Internet layer
    • Encapsulate as IP Packet
    • Attach IP header which contains source and destination host IP addresses

     

     

     

  • The Sending and Receiving Process
  • Network Access Layer
    • Frames will be encapsulated with frame
      header and trailer.
    • Frame header contains a source and destination physical address.
    • Trailer contains a source and destination physical address
    • Bits encoded to Ethernet media by the server NIC
  • The OSI Model

 

 

 

  • Design by International Organization for Standardization (ISO) o provide a framework on which to build a suite of open systems protocols.

 

  • The OSI Model
  • Application Layer
    • Provides the means for end-to-end connectivity between individuals in the human network using data networks.
  • Presentation Layer
    • Provides for common representation of the data transferred between Application layer services.
  • Session layer
    • Provides services to the Presentation layer to organize its dialogue and to manage data exchange.
  • Transport layer
    • Defines services to segment, transfer, and reassemble the data for individual communications between the end devices.

 

  • The OSI Model
  • Network layer
    • Provides services to exchange the individuals pieces of data over the network between identified end devices.
  • Data Link protocol
    • Describes methods for exchanging data frames between devices over a common media
  • Physical layer
    • Describe the mechanical, electrical, functional and procedural means to activate, maintain and deactivate physical-connections for bit transmission to and from a network device.
  • Comparing TCP/IP and OSI Model
  • Comparing TCP/IP and OSI Model
  • TCP/IP protocol does not specify which protocols to use when transmitting over a physical medium.
  • The only key parallel layer are in the Transport and Network layers.
  • The TCP/IP Application layer includes a number of protocols that provide specific functionality to a variety of end user applications.
  • The OSI model Layers 5, 6 and 7 are used as references for application software developers and vendors to produce products that need to access networks for communications.
  • Network Addressing
  • Data is being divided into several places.
  • It is critical for each piece of data to contain enough identifying information to get it to the correct destination.
  • There are various types of addresses that must be included to successfully deliver the data from a source application running on one host to the correct destination application running on another.
  • Network Addressing
  • Addressing Process:
    • Getting the Data to End Devices
    • Getting the Data Through the Internetwork
    • Getting the Data to the Right Application
  • Network Addressing
  • Network Addressing
  • Getting Data to the End Device
    • Handles by the Layer 2 in OSI Model (Data link)
    • The first identifier, the host physical address, is contained in the header of the Layer 2 PDU, called a frame.
    • Layer 2 addresses are used to communicate between devices on a single local network
    • The Layer 2 address is unique on the local network and represents the address of the end device on the physical media.
    • Uses Media Access Control (MAC) Address to refer to end device.

     

  • Network Addressing
  • Getting Data to the End Device
  • Network Addressing
  • Getting Data through Internetwork
    • Handles by OSI Layer 3 (Network layer)
    • Layer 3 protocols are primarily designed to move data from one local network to another local network within an internetwork.
    • Include identifiers that enable intermediary network devices to locate hosts on different network through IP Address. Packet header holds this information.
    • Intermediary devices served as boundary of each local network.

     

  • Network Addressing
  • Getting Data through Internetwork
  • Network Addressing
  • Getting Data to the Right Application
    • Handles by the OSI Model Layer 4(Transport layer).
    • Identify is the specific process or service running on the destination host device that will act on the data being delivered.
    • Layer 4identify is the specific process or service running on the destination host device that will act on the data being delivered.
    • It enables individual processes running on the source and destination hosts communicate with each other.
    • Each application or service is represented at Layer 4 by a port number.
    • Port are typically used to identify a certain process or service on a computer.

     

  • Network Addressing
  • Getting Data to the Right Application
  • Chapter 3:
    Application Layer Functionality and Protocol
  • John D. Tajones
  • Central Mindanao University
  • Chapter Introduction

 

  • In this chapter, we will focus on the role of one layer, the Application layer and its components:
    • Applications
    • Services
    • Protocols
  • These chapter will explore how these three elements make the robust communication across the information network possible.
  • Chapter Introduction
  • Chapter Objectives:
    • Describe how the functions of the three upper OSI model layers provide network services to end user applications.
    • Describe how the TPC/IP Application layer protocols provide the services specified by the upper layers of the OSI model.
    • Define how people use the Application Layer to communicate across the information network.
    • Describe the function of well-known TCP/IP applications, such as the World Wide Web and email, and their related services (HTTP, DNS, SMB, DHCP, STMP/POP, and Telnet).
  • Chapter Introduction
  • Chapter Objectives:
    • Describe file-sharing process that use peer-to-peer applications and the Gnutella protocol.
    • Explain how protocol ensure services running on one kind of device can send to and receive data from many different network devices.
    • Use network analysis tools to examine and explain how common user applications work.
  • The Application Layer
  • Applications: The Interface Between the Networks

 

  • The Application layer is the the 7th in the OSI Model and top of the TCP/IP model.
  • It is the layer that provides the interface between the applications.
  • Application layer protocols are used to exchange data between programs running on the source and destination hosts

 

  • Applications: The Interface Between the Networks
  • Applications: The Interface Between the Networks
  • The Presentation Layer 3 Primary Functions
    • Coding and conversion of Application layer data to ensure data interpretation to the right application
    • Compression of the data in a manner that can be decompressed by the destination device.
    • Encryption of the data for transmission and the decryption of data upon receipt by the destination.
  • The Session Layer
    • Create and maintain dialogs between source and destination applications.
    • handles the exchange of information to initiate dialogs, keep them active, and to restart sessions that are disrupted or idle for a long period of time.
  • Applications: The Interface Between the Networks
  • Applications: The Interface Between the Networks
  • TCP/IP Application layer protocols are those that provide for the exchange of user information and specify format and information for internet communication functions.
  • TCP IP Application Layer Protocols
    • Domain Name Service (DNS) Protocol is used to resolve Internet names to IP addresses.
    • Hypertext Transfer Protocol (DNS) is used to transfer files that make up the Web pages of the World Wide Web.
    • Simple Mail Transfer Protocol (SMTP) is used for the transfer of mail messages and attachments.
    • Telnet, a terminal emulation protocol, is used to provide remote access to servers and networking devices.
  • Application Layer Software
  • Network-Aware Applications
    • Software programs used by people to communicate over the network.
    • It implement the application layer protocols and are able to communicate directly with the lower layers of the protocol stack.
    • E.g; e-mail clients and web browsers
  • Application layer services
    • Programs that interface with the network and prepare the data for transfer.
    • Data (e.g. text, graphics, or video) require different network services to ensure that it is properly prepared for processing by the functions occurring at the lower layers of OSI model.
  • User Applications, Services, and Protocol
  • User Applications provides means for the user to create the message and application layer services establish an interface to the network, protocol provide the rules and formats that govern how data is treated.
  • Application layer relies on the functions of the lower layers in order to complete the communication process.

 

  • Application Layer Protocol Functions
  • User Applications provides means for the user to create the message and application layer services establish an interface to the network, protocol provide the rules and formats that govern how data is treated.
  • Application layer relies on the functions of the lower layers in order to complete the communication process.

 

  • Application Layer Protocol Functions
  • Client/Server Model
  • Client/Server Model
  • Device requesting the information is called a client and the device responding to the request is called a server.
  • Client and server processes are considered to be in the Application layer.
  • Example:
    • corporate environment where employees use a company e-mail server to send, receive and store e-mail
  • Servers
  • Servers
  • In a general networking context, any device that responds to requests from client applications is functioning as a server
  • Different types of server applications may have different requirements for client access.
  • Server daemons
    • It is a process/service typically run in the background and are not under an end user’s direct control.
    • Described as “listening” for a request from a client, because they are programmed to respond whenever the server receives a request for the service provided by the daemon.
  • Servers
  • Peer-to-peer Networking and Applications (p2p)
  • Peer-to-peer model 2 distinct forms
    • peer-to-peer network design
    • peer-to-peer applications (P2P)
    • (Both forms have similar features but in practice work very differently.)
  • Peer-to-Peer Networks
    • two or more computers (devices) are connected via a network and can share resources (such as printers and files) without having a dedicated server.
    • One computer might assume the role of server for one transaction while simultaneously serving as a client for another

     

  • Peer-to-peer Networking and Applications (p2p)
  • Peer-to-peer Networking and Applications (p2p)
  • Peer-to-peer model 2 distinct forms
    • peer-to-peer network design
    • peer-to-peer applications (P2P)
    • (Both forms have similar features but in practice work very differently.)
  • Peer-to-Peer Networks
    • two or more computers (devices) are connected via a network and can share resources (such as printers and files) without having a dedicated server.
    • One computer might assume the role of server for one transaction while simultaneously serving as a client for another

     

  • Peer-to-peer Networking and Applications (p2p)

 

  • Peer-to-peer applications
    • It allows a device to act as both a client and a server within the same communication.
    • Every client is a server and every server a client. Both can initiate a communication and are considered equal in the communication process.
  • Peer-to-peer Networking and Applications (p2p)
  • DNS Services and Protocol
    • Transport layer uses an addressing scheme called a port number.
    • Port number identify applications and Application layer services that are the source and destination of data.
    • Services Port Numbers:
      • Domain Name System (DNS) – TCP/UDP Port 53
      • Hypertext Transfer Protocol (HTTP) – TCP Port 80
      • Simple Mail Transfer Protocol (SMTP) – TCP Port 25
      • Simple Mail Transfer Protocol (SMTP) – TCP Port 25

       

  • DNS Services and Protocol
    • Services Port Numbers:
      • Post Office Protocol (POP) – UDP Port 110
      • Telnet – TCP Port 23
      • Dynamic Host Configuration Protocol – UDP Port 67
      • File Transfer Protocol (FTP) – TCP Ports 20 and 21
  • DNS
    • In data networks, devices are labeled with numeric IP addresses, so that they can participate in sending and receiving messages over the network.

       

       

  • DNS Services and Protocol
  • DNS
    • Domain names were created to convert the numeric address into a simple, recognizable name.
    • Used to resolve addresses
  • DNS protocol
    • defines an automated service that matches resource names with the required numeric network address.
    • includes the format for queries, responses, and data formats
  • DNS Services and Protocol
  • DNS
    • A DNS server provides the name resolution using the name daemon, which is often called named.
    • DNS server stores different types of resource records used to resolve names:
      • A – an end device address
      • NS – an authoritative name server
      • CNAME – canonical name (or Fully Qualified Domain Name) for an alias; used when multiple services have the single network address but each service has its own entry in DNS
      • MX – mail exchange record; maps a domain name to a list of mail exchange servers for that domain
  • DNS Services and Protocol
  • DNS

 

 

 

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