02. communicating over the network

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Communicating over theNetwork

Network Fundamentals Chapter 2Tim Horgan

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Gradebook


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Objectives

! Describe the structure of a network, including thedevices and media that are necessary for successfulcommunications.

! Explain the function of protocols in networkcommunications.

! Explain the advantages of using a layered model todescribe network functionality.

!Describe the role of each layer in two recognizednetwork models: The TCP/IP model and the OSImodel.

! Describe the importance of addressing and namingschemes in network communications.

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! Communication begins with a message, or information, thatmust be sent from one individual or device to another.

3 common elements of communication message sourcethe channel (media)

message destination

! Networks: data or information networks capable of carryingmany different types of communications

Network Structure


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Network Structure!Data is sent across a network in small chunks called

segments

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Network Structure!Devices and media are the physical elements or

hardware of the network.

Network componentshardware

software


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Network Structure!Services and processes are the communication

programs, called software, that run on the networkeddevices.

!Services include many of the common networkapplications people use every day, like e-mail hostingservices and web hosting services.

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Network Structure

! End devices form the interface between the human network andthe underlying communication network.

! Some examples of end devices are: Computers (workstations, laptops, file servers, web servers) Network printers VoIP phones Security cameras Mobile handheld devices (wireless barcode scanners, PDAs)

! In modern networks, a host can act as a client, a server, or both.Software installed on the host determines which role it plays on thenetwork.

! Servers are hosts that have software installed that enables them toprovide information and services, like e-mail or web pages, to otherhosts on the network.


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Network Structure

! Intermediary devices are used to provide connectivityand to work behind the scenes to ensure that data flowsacross the network.

!These devices connect the individual hosts to thenetwork and can connect multiple individual networks toform an internetwork.

!Examples of intermediary network devices are: Network Access Devices (Hubs, switches, & wireless APs) Internetworking Devices (routers) Communication Servers and Modems Security Devices (firewalls)

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Network Structure

!Processes running on the intermediary network devicesperform these functions:

Regenerate and retransmit data signals Maintain information about what pathways exist 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


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Network Structure

!Modern networks primarily use three types of media: Metallic wires within cables Glass or plastic fibers (fiber optic cable) Wireless transmission

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Network Structure

!The signal encoding that must occur for the message tobe transmitted is different for each media type.

!Not all network media has the same characteristics andis appropriate for the same purpose.

!Criteria for choosing a network media are: The distance the media can successfully carry a signal. The environment in which the media is to be installed.Amount of data and the speed at which it must be

transmitted.

The cost of the media and installation


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Network Types

!Local Area Networks (LANs)- Network serving a home, building or campus is considered a (LAN)

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Network Types

!Wide Area Networks (WANs)- LANs separated by geographic distance are connected by a

network known as a Wide Area Network (WAN)


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Network Types

!The InternetDefined as a global mesh of interconnected networks

!The term intranet is often used to refer to a privateconnection of LANs and WANs that belongs to anorganization and is designed to be accessible only by theorganization's members, employees, or others withauthorization.

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Network Types

!Common Data Network Symbols


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Network Types

! In addition to these representations, specialisedterminology is used when discussing how each of thesedevices and media connect to each other.

! Important terms to remember are: Network Interface Card - A NIC, or LAN adapter, provides

the physical connection to the network at the PC or other hostdevice. The media connecting the PC to the networkingdevice plugs directly into the NIC.

Physical Port - A connector or outlet on a networking devicewhere the media is connected to a host or other networkingdevice.

Interface - Specialised ports on an internetworking devicethat connect to individual networks. Because routers are usedto interconnect networks, the ports on a router are referred tonetwork interfaces.

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Function of Protocol in Network Communication

!The importance of protocols and how they are used tofacilitate communication over data networks

A protocol is a set of predetermined rules.


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!A group of inter-related protocolsthat are necessary to perform acommunication function is calleda protocol suite.

!These protocols areimplemented in software andhardware that is loaded on eachhost and network device.

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!Networking protocols suites describe processes such as: The format or structure of the message The process by which networking devices share information

about pathways with other networks How and when error and system messages are passed

between devices

The setup and termination of data transfer sessions! Individual protocols in a protocol suite may be vendor-

specific and proprietary.

The use of standards in developing and implementing protocolsensures that products from different manufacturers can worktogether for efficient communications.

Ratified by a standards organisation, such as the Institute ofElectrical and Electronics Engineers (IEEE) or the InternetEngineering Task Force (IETF).


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!Example: interaction between web server & browser.!This interaction uses a number of protocols and

standards in the process of exchanging information.

!The different protocols work together to ensure that themessages are received and understood by both parties.

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! Application Protocol: HTTP defines the content and formatting ofthe requests and responses exchanged between the client andserver. Both the client and the web server software implement HTTP.

! Transport Protocol: TCP divides the HTTP messages into smallerpieces, called segments, to be sent to the destination client. It is alsoresponsible for controlling the size and rate at which messages areexchanged between the server and the client.

! Internetwork Protocol: IP is responsible for taking the formattedsegments from TCP, encapsulating them into packets, assigningaddresses, and selecting the best path to the destination host.

! Network Access Protocols: Data-link management protocols takepackets from IP and format them to be transmitted over the media.


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Technology Independent Protocols

!Many diverse types of devices can communicate usingthe same sets of protocols. This is because protocolsspecify network functionality, not the underlyingtechnology to support this functionality.

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Layers with TCP/IP and OSI Model!Benefits of using a layered model

assists in protocol design fosters competition changes in one layer do not affect other layers provides a common language


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Protocols & Reference Models

!A reference model provides a common reference formaintaining consistency within all types of networkprotocols and services.

!A protocol model provides a model that closelymatches the structure of a particular protocol suite.

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TCP/IP Model

!TCP/IP was the first layered protocol model, early1970s, referred to as the Internet model.

!Defines four categories of functions that must occur forcommunications to be successful.


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Layers with TCP/IP and OSI Model

!TCP/IP protocols, which are implemented on boththe sending and receiving hosts, interact to provideend-to-end delivery of applications over a network.

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Data Encapsulation & PDUs

!As application data is passed down the protocol stack on its way tobe transmitted across the network media, various protocols addinformation to it at each level. This is commonly known as the

encapsulation process.


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The sending & receiving process

!When sending messages on a network, the protocolstack on a host operates from top to bottom.

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The sending & receiving process

!This process is reversed at the receiving host.!The data is decapsulated as it moves up the stack

toward the end user application.


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Using Layered Models

OSI Model

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Using Layered Models

OSI Model


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Layers with TCP/IP and OSI Model

!The protocols that make up the TCP/IP protocol suitecan be described in terms of the OSI reference model.

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Addressing and Naming Schemes

!There are various types of addresses that must beincluded to successfully deliver the data from a sourceapplication running on one host to the correctdestination application running on another.

!Using the OSI model as a guide, we can see thedifferent addresses and identifiers that are necessary ateach layer.


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!Ethernet MAC Addresses, IP Addresses, and TCP/UDPPort numbers

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!Labels in encapsulation headers are used to managecommunication in data networks


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!At Layer 4, information contained in the PDU headeridentifies the specific process or service running onthe destination host device that will act on the databeing delivered.

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Summary

02. communicating over the network

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