CA Ex S1M02 Communicating Over the Network

7/28/2019 CA Ex S1M02 Communicating Over the Network

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Chapter 2- Communicating over the Network

CCNA Exploration 4.0


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Hc vin mng Bach Khoa - Website: www.bkacad.com

Objectives

Describe the structure of a network, including the devicesand 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 recognized networkmodels: The TCP/IP model and the OSI model.

Describe the importance of addressing and namingschemes in network communications.


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The Platform for Communication


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The Elements of Communication

1. Message source (sender)

2. The channel

3. Message destination (receiver)

2.1.1


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Communicating the Messages

A better approach is to divide the data intosmaller, more manageable pieces to send over the

network. This division of the data stream intosmaller pieces is called segmentation.

Segmenting messages has 2 primary benefits:

First, by sending smaller individual pieces fromsource to destination, many different

conversations can be interleaved on the

network. (multiplexing)Second, segmentation can increase the

reliability of network communications.


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2.1.2


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Components of the Network

Hardware: Devices and media

Software: Services and processes


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Media: Physical elements, often visible but occasionallynot be visible.


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Services and processes: are the communicationprograms, called software, that run on the networked

devices.


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A network service provides information in response to a request. Services include many of the common network applicationspeople

use every day, like e-mail hosting services and web hostingservices.

Processes provide the functionalitythat directs and moves themessages through the network. Processes are less obvious to us but are critical to the operation of

networks.


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Extra: Windows service

A Windows service is an applicationthat starts when the Microsoft Windowsoperating system is booted and runs in the backgroundas long as Windows isrunning.

Typically, it does not have a user interface and is a long-running executable

application that can run in its own session. It is very similar in concept to a Unixdaemon.


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Extra: Windows service


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Extra: ProcessExplorer tool


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End Devices and their Role on the Network

The network devices that people are most familiar with arecalled end devices. These devices form the interface

between the human network and the underlying

communication network.

Some examples of end devices are:Computers (work stations, laptops, file servers, web

servers)Network printers

VoIP phones

Security camerasMobile handheld devices (such as wireless barcode

scanners, PDAs)

2.1.4


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End Devices and their Role on the Network

Host: In the context of a network, end devices arereferred to as hosts. A host device is either the

source or destination of a message transmitted

over the network.

Servers are hosts that have software installed thatenables them to provide information and services,

like e-mail or web pages, to other hosts on thenetwork.

Clients are hosts that have software installed thatenables them to request and display theinformation obtained from the server.


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Intermediary Devices and their Role on the Network

Intermediary devices to provide connectivity and to workbehind the scenes to ensure that data flows across thenetwork.

These devices connect the individual hosts to the networkand can connect multiple individual networks to form an

internetwork.

Examples of intermediary network devices are:Network Access Devices (Hubs, switches, and

wireless access points)

Internetworking Devices (routers)Communication Servers and Modems

Security Devices (firewalls)

2.1.5


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Intermediary Devices and their Role on the Network

Processes running on the intermediary network devicesperform these functions:

1. Regenerate, retime and retransmit data signals2. Maintain information about what pathways existthrough the network and internetwork

3. Notify other devices of errors and communicationfailures

4. Direct data along alternate pathways when there is alink failure

5. Classify and direct messages according to QoSpriorities

6. Permit or deny the flow of data, based on securitysettings


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Networking Media


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Networking Media

Criteria for choosing a network media are:

1. The distance the media can successfully carry a signal.2. The environment in which the media is to be installed.3. The amount of data and the speed at which it must be

transmitted.4. The cost of the media and installation.


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Networking Media

The signal

encoding

that must occurfor the messageto betransmitted isdifferent foreach media

type.

2.1.6


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LAN, WAN and Internetworks


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Networks infrastructures

Networks infrastructures can varygreatly in terms of:

1. The size of the area covered

2. The number of users connected

3. The number and types of servicesavailable


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Local Area Networks

Local Area Network (LAN): An individual network usuallyspans a single geographical area, providing services and

applications to people within a common organizationalstructure, such as a single business, campus or region


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LAN

A LAN is usually in a single geographicalarea.

The network is administered by a singleorganization.

A LAN provides network services andaccess to applications for users within acommon organization.



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Wide Area Networks

LANs separated by geographic distance are connected by a networkknown as a Wide Area Network (WAN).

WANs use specifically designed network devices to make theinterconnections between LANs.

Telecommunications Service Provider (TSP)


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Q/A

TSP ISP (Internet Service Provider)

OSP (Online Service Provider) IXP (Internet Exchange Provider)



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The Internet A Network of Networks

Although there are benefits to using a LAN or WAN, mostof us need to communicate with a resource on anothernetwork, outside of our local organization.

Examples of this type of communication include:Sending an e-mail to a friend in another country

Accessing news or products on a website

Getting a file from a neighbor's computer

Instant messaging with a relative in another city

Following a favorite sporting team's performance on

a cell phone


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The Internet A Network of Networks

A global mesh of interconnected networks (internetworks)meets these human communication needs.

The Internet is created by the interconnection of networksbelonging to Internet Service Providers (ISPs).

Intranet is often used torefer to a private

connection of LANs andWANs that belongs to anorganization, and isdesigned to be

accessible only by theorganization's members,employees, or others withauthorization.


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Network Representations


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Lab 2.2.4.2

In this activity, you will gain experience with data networksymbols by creating a simple logical topology.


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Extra: ping

Verifies IP-level connectivity to another TCP/IP computer by sendingInternet Control Message Protocol (ICMP) Echo Request messages.The receipt of corresponding Echo Reply messages are displayed,

along with round-trip times.

ping 127.0.0.1 This ping is unique and is called an internal loopback test. It verifies the

operation of the TCP/IP stack and NIC transmit/receive function.

ping IP-address-of-host-computer A ping to a host PC verifies the TCP/IP address configuration for the local

host and connectivity to the host.

ping default-gateway-IP-address A ping to the default gateway verifies whether the router that connects the

local network to other networks can be reached.

ping remote-destination-IP-address A ping to a remote destination verifies connectivity to a remote host.


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Lab 2.2.5: tracert

Determines the path taken to a destination by sending Internet ControlMessage Protocol (ICMP) Echo Request messages to the destination withincrementally increasing Time to Live (TTL) field values.


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Lab 2.2.5

This lab also assumes the installation of NeoTrace.


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http://www.ip-1.com/



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Extra: nslookup

Displays information that you can use to diagnose Domain NameSystem (DNS) infrastructure. Before using this tool, you should befamiliar with how DNS works. The Nslookup command-line tool isavailable only if you have installed the TCP/IP protocol.

E ARP


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Extra: ARP

Displays and modifies entries in the Address Resolution Protocol(ARP) cache, which contains one or more tables that are used to storeIP addresses and their resolved Ethernet or Token Ring physicaladdresses. There is a separate table for each Ethernet or Token Ringnetwork adapter installed on your computer.

E t N t t t


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Extra: Netstat

Displays active TCP connections, ports on which the computer islistening, Ethernet statistics, the IP routing table, IPv4 statistics (for theIP, ICMP, TCP, and UDP protocols), and IPv6 statistics (for the IPv6,ICMPv6, TCP over IPv6, and UDP over IPv6 protocols).

E t t h


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Extra: netsh

You can use commands in the Netsh Interface IP context to configure theTCP/IP protocol (including addresses, default gateways, DNS servers, andWINS servers) and to display configuration and statistical information.


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Protocols

Rules that Govern Communications


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Protocol suite: a group of inter-related protocolsthat are necessary to perform a communication

function. Protocols are implemented in software and hardware

that is loaded on each host and network device.

The protocols are viewed as a layered hierarchy,with each higher level services depending on the

functionality defined by the protocols shown in the

lower levels.

2.3.1



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Network Protocols


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Network Protocols

1. The format or structure of the message2. The process by which networking devices

share information about pathways with othernetworks

3. How and when error and system messagesare passed between devices

4. The setup and termination of data transfersessions

Networking protocols suites describe processes such as:

Network Protocols


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Network Protocols

2.3.2

Network Protocols


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Network Protocols

Network Protocols


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Network Protocols

Network Protocols


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Network Protocols

Protocol Suites and Industry Standards


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Protocol Suites and Industry Standards

Many of the protocols that comprise a protocolsuite reference other widely utilized protocols or

industry standards. A standard is a process or protocol that has beenendorsed by the networking industry and ratified

by a standards organization, such as IEEE orIETF.

The use of standards in developing and

implementing protocols ensures that products fromdifferent manufacturers can work together for

efficient communications.

2.3.3

The Interaction of Protocols


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The Interaction of Protocols

2.3.4

Technology Independent Protocols


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Technology Independent Protocols

Many diverse types of devices can communicate using the samesets of protocols.

This is because protocols specify network functionality, not theunderlying technology to support this functionality.

2.3.5


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Using Layered Models

The Benefits of Using a Layered Model


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The Benefits of Using a Layered Model

1. Assists in protocol design.2. Fosters competition because products from

different vendors can work together.

3. Prevents technology or capability changes inone layer from affecting other layers aboveand below.

4. Provides a common language to describenetworking functions and capabilities.

2.4.1

Protocol and Reference Models


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A protocol model provides a model thatclosely matches the structure of a particularprotocol suite. Example: TCP/IP

A reference model provides a commonreference for maintaining consistency withinall types of network protocols and services.The primary purpose of a reference model is to

aid in clearer understanding of the functionsand process involved.

There are 2 basic types of networking models:



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The Open Systems Interconnection (OSI)model is the most widely known

internetwork reference model. It is used for

Data network design

Operation specifications Troubleshooting.



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The TCP/IP Model


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The Communication Process


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1.Creation of data2.Segmentation and encapsulation3.Generation of the data onto the media4.Transportation

5.Reception of the data6.Decapsulation and reassembe

7.Passing this data to the destinationapplication

2.4.4

Protocol Data Units and Encapsulation


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Encapsulation process:application data is passed down the protocol

stack on its way to be transmitted across the

network media, various protocols addinformation to it at each level

The form that a piece of data takes at any layer iscalled a Protocol Data Unit (PDU). The PDUs are named according to the protocols

of the TCP/IP suite: Data, Segement, Packet,Frame, Bit

Extra: Peer-to-peer communications


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Extra: Detailed encapsulation process


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Extra: Data Encapsulation Example


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ApplicationHeader + data

010010100100100100111010010001101000

Application Layer

Layer 4: Transport Layer

Layer 3: Network Layer

Layer 2:Network

Layer

Layer 1: Physical

Layer

Extra: abount network protocols


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1.Define the structure of layer specificPDU's

2.Outline the functions necessary for

communications between layers3.Require layer dependent encapsulations

Extra: Two functions of encapsulation


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1.Identifies pieces of data as part of thesame communication

2.Ensures that data pieces can be directed

to the correct receiving end device


The Sending and Receiving Process


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Step 1:2.4.6



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Step 2



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Step 3



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Step 4



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Step 5:



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Step 6:



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Step 7:



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Step 8:



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Step 9:



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Step 10:

The OSI Model


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2.4.7

The OSI Model


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The OSI Model


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http://www.tcpipguide.com/free/t_SessionLayerLayer5.htm


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The OSI Model


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The OSI Model


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The OSI Model


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The OSI Model


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Comparing the OSI Model with TCP/IP Model


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2.4.8

Comparing the OSI Model with TCP/IP Model


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Lab 2.4.8.2


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In this activity, you will see how Packet Tracer uses theOSI Model as a reference to display the encapsulationdetails of a variety of the TCP/IP protocols.


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Network Addressing

Addressing in the Network

Th i f dd h b i l d d


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There are various types of addresses that must be included tosuccessfully deliver the data from a source application running on onehost to the correct destination application running on another.

Using the OSI model as a guide, we can see the different addressesand identifiers that are necessary at each layer.

Getting the Data to the End Device


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During the process of encapsulation, address identifiers are added to

the data as it travels down the protocol stack on the source host. Multiple layers of addressing to ensure its delivery: Ethernet MAC Addresses, IP Addresses TCP/UDP Port numbers

Getting the Data through the Internetwork

E l ti h d d t


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Encapsulation headers are used to managecommunication in data networks

2.5.3

Getting the Data to the Right Application


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2.5.4

Warriors of the Net

warriors-700-VBR 1 mpg


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See also: Proxy Server URL

warriors-700-VBR_1.mpg

2.5.5

Lab 2.6.1


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Lab 2.6.2: Introduction to Wireshark tool


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Lab 2.7.1


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Q&A

The statements that are correct


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The statements that are correctconcerning network protocols:

1. define the structure of layerspecific PDU's

2. outline the functions necessary forcommunications between layers

3. require layer dependentencapsulations


Q&A

Two functions of encapsulation


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Two functions of encapsulation1. identifies pieces of data as part

of the same communication

2. ensures that data pieces canbe directed to the correctreceiving end device


Q&A

What is a primary function of the


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What is a primary function of thetrailer information added by the

data link layer encapsulation?

supports error detection


Q&A

What is a PDU?


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What is a PDU?a layer specific encapsulation


Q&A

What is the purpose of the TCP/IP


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What is the purpose of the TCP/IPNetwork Access layer?

network media control


Q&A

What is the proper order of the


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What is the proper order of thelayers of the OSI model from the

highest layer to the lowest layer?

application, presentation,

session, transport, network, datalink, physical


Summary


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Documents

CA Ex S1M02 Communicating Over the Network