Itacademy Course

7/31/2019 Itacademy Course

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IT Career Path

Network Administrator IT Administrator

Technical Support

Voice Administrator

Security Administrator


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CCNA (Cisco Certified Network Associate )

CCNP (Cisco Certified Network Professional)

CCIE (Cisco Certified Internetwork Expert)

Network Administrator


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IT Administrator


MCITP ( Enterprise Administrator)

Microsoft Exchange

Microsoft ISA

UNIX


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Technical Support

A+


MCITP ( Enterprise Administrator)


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Voice Administrator

CCNA Voice (Cisco Certified Network Associate Voice )

CCNP Voice(Cisco Certified Network Professional Voice)

CCIE Voice (Cisco Certified Internetwork Expert Voice)


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Security Administrator

CCNA Security (Cisco Certified Network Associate Security)

CCNP Security (Cisco Certified Network Professional Security)

CCIE Security (Cisco Certified Internetwork Expert Security)


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IT Essentials


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Computercases


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ComputerPower Supply


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Different connectors are used to connect specific

components and various locations on the motherboard:


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Different connectors are used to connect specificcomponents and various locations on the motherboard:


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motherboards


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CPU


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CPU


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cooling systems


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ROM and RAM


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AdaptercardsNIC

Wireless NIC:

Sound adapter :

Video adapter:

Modem adapter


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Network Interface Card (NIC)

PCI

USB Wireless


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Storagedrives

Floppy drive

Hard drive Optical drive Flash drive


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internalcables

Floppy disk drive (FDD) data cable PATA (IDE) data cable PATA (EIDE) data cable SATA data cable

SCSI data cable


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inputdevices

Mouse and keyboard Digital camera and digital video camera Touch screen Scanner


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Output devices

Monitors and projectors Printers, scanners, and fax machines Speakers and headphones


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2007 Cisco Systems, Inc. All rights reserved. Cisco Public

ITE PC v4.0

Chapter 1 26

Network

Fundamentals


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Chapter 1 27 2007 Cisco Systems, Inc. All rights reserved. Cisco Public

Introduction

resources available through the Internet can help you :


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What is Communication ?

Communication in our daily lives takes many forms and occurs in

many environments. We have different expectations depending on

whether we are chatting via the Internet or participating in a job

interview. Each situation has its corresponding expected behaviorsand styles.

allnetworks have four basic elements in common

1- Message2-Devices

3-Medium

4-Rules or Protocols


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Message

units of information that travel from one device to another

our instant message gets converted into a format that can be

transmitted on the network

All types of messages must be converted to bits, binary coded digital

signals, before being sent to their destinations.

no matter what the original message format was: text, video, voice, or

computer data

Once our instant message is converted to bits, it is ready to be sent

onto the network for delivery


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Devices

Switch : the most common device for interconnecting local area

networks

Firewall : provides security to networks

Router : helps direct messages as they travel across a network

Wireless Router : a specific type of router often found in home

networks


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Medium

A means of interconnecting these devices that can transport themessages from one device to another

To send our message to its destination, the computer must be connected

to a wired or wireless local network.

Wireless networks allow the use of networked devices anywhere in an

office or home, even outdoors

Ethernet is the most common wired networking technology

The wires, called cables, connect the computers and other devices thatmake up the networks.

Wired networks are best for moving large amounts of data at high

speeds, such as are required to support professional-quality multimedia.


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Medium

1- wired

Copper :

which carries electrical signals

- twisted pair telephone wire

- coaxial cable- Category 5 Unshielded Twisted Pair (UTP) cable

optical fiber :

which carries light signals

- glass- plastic

2- Wireless :

the medium is the Earth's atmosphere, or space, and the signals are

microwaves


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Rules or Protocols

We have different expectations depending on whether we are chatting via

the Internet or participating in a job interview. Each situation has its

corresponding expected behaviors and styles.

Among the protocols that govern successful human communication are:

An identified sender and receiver

Agreed upon method of communicating (face-to-face, telephone, letter)

Common language and grammar

Speed and timing of delivery

Confirmation or acknowledgement requirements (important , Less

important )

Communication between individuals is determined to be successful when

the meaning of the message understood by the recipient matches the

meaning intended by the sender.


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Rules or Protocols

rules are the standards and protocols that Govern how the messages are

sent

standards and protocols Govern how messages are directed through the

network

standards and protocols Govern how messages are interpreted at the

destination devices

Protocols are the rules that the networked devices use to communicate

with each other.

Ex.: HTTP SMTP XMPP - SIP


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Multiple services-multiple networks :

Traditional telephone, radio, television, and computer data networkseach have their own individual versions of the four basic network

elements.

every one of these services required a different technology to carry its

particular communication signal. Additionally, each service had its own

set of rules and standards to ensure successful communication of itssignal across a specific medium.

Converged networks :

Technology advances are enabling us to consolidate these disparate

networks onto one platform - a platform defined as a converged

network.

The flow of voice, video, and data traveling over the same network

eliminates the need to create and maintain separate networks.

personal computers, phones, TVs, personal assistants, and retail point-of-

sale registers - but only one common network infrastructure.


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there are four basic characteristics that the underlying

architectures need to address in order to meet user

expectations:

Fault Tolerance

Scalability

Quality of Service (QoS)

Security


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Fault Tolerance

always available to the millions of users

limits the impact of a hardware or software failure and can recover quickly

when such a failure occurs.

depend on redundant links, or paths, between the source and destinationof a message.

Both the physical infrastructures and the

logical processes that direct the messages

through the network are designed toaccommodate this redundancy


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Scalability

A scalable network can expand quicklyto support new users and

applications without impacting the performance of the service being

delivered to existing users.

(QoS ) Quality of Service

The Internet is currently providing an acceptable level of fault tolerance andscalability for its users.

But new applications available to users over internetworks create higher

expectations for the qualityof the delivered services.

Voice and live video transmissions require a level of consistent quality anduninterrupted delivery that was not necessary for traditional computer

applications.

Quality of these services is measured against the quality of experiencing the

same audio or video presentation


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Security

Prevent unauthorized disclosure or theft of information

Prevent unauthorized modification of information

Prevent Denial of Service


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a single communication :

such as a music video or an e-mail message, could be sent across a

network from a source to a destination as one massive continuous stream

of bits.

If messages were actually transmitted in this manner , it would mean

that no other device would be able to send or receive messages on the

same network while this data transfer was in progress.

These large streams of data would result in significant delays. Further, if alink in the interconnected network infrastructure failed during the

transmission, the complete message would be lost and have to be

retransmitted in full.


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Packet Switched Connectionless Networks :

a single message can be broken into multiple message blocks .

Individual blocks containing addressing information indicate both their

origination point and their final destination .

Using this embedded information, these message blocks, called packets,

can be sent through the network along various paths .

and can be reassembled into the original message upon reaching their

destination .


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Utilizing Packets :

Each packet is sent independentlyfrom one switching location to

another.

a routing decision is made as towhich path to use to forward the

packet towards its final destination.

If a previously used path is no longer available, the routing function

can dynamically choose the next best available path. Because the

messages are sent in pieces.

rather than as a single complete message, the few packets that may

be lost in the advent of a failure can be retransmitted to the

destination along a different path. In many cases, the destination

device is unaware that any failure or rerouting has occurred.


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A better approach is to divide the data into smaller .

more manageable pieces to send over the network.

This division of the data stream into smaller pieces is called segmentation.Segmenting messages has two primary benefits.

Multiplexing

Segmentation


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Quality of Service : ensuring (QoS) requires a set of techniques to manage the utilization of

network resources.

In order to maintain a high quality of service for applications that require it.

it is necessary to prioritize which types of data packets must be delivered at

the expense of other types of packets that can be delayed or dropped.

Classification:

we classify applications in categories based on specific quality of service

requirements.

For example :communication that is time-sensitive or important would be

classified differently from communication that can wait or is of lesser

importance.


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Assigning Priorities :

Ex : the delivery of a movie uses a relatively large amount of network resources

when it is delivered continuously without interruption.

Voice Over IP

Financial Transaction

Web Page Browsing


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In network communications, each segment of the message must go

through a similar process to ensure that it gets to the correct destination

and can be reassembled into the content of the original message.

enddevices are referred to as hosts

A host device is either the source or destination of a message transmitted

over the network. In order to distinguish one host from another, each

host on a network is identified by an address

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)


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Local Area Network (LAN)

A LAN is usually administered by a single organization. The administrative

control that governs the security and access control policies are enforced on

the network level.

Wide Area Network (WAN)

When a company or organization has locations that are separated by large

geographical distances, it may be necessary to use a telecommunicationsservice provider ( ) to interconnect the LANs at the different locations


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The Internet

is created by the interconnection of networks belonging to Internet Service

Providers (ISPs).

Intranet

a private connection 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 Interface Card - A NIC, or LAN adapterprovides the physical connection to the network at the PC or other host

device. The media connecting the PC to the networking device plugs directly

into the NIC.


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Physical Port

A connector or outlet on a networking device where the media is connected

to a host or other networking device.

Types of Data Communication

Simplex Communication System :

Half Duplex Communication System

Full Duplex Communication System

Communication is possible only in one direction ( TV. And Radio )

At any given time user can only transmit or receive (Police Radio)

Simulation two way communication is allowed


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Rules That Govern Communication

Successful communication between hosts on a network requires theinteraction of many different protocols.

A group of inter-related protocols that are necessary to perform a

communication function is called a protocol suite

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.

The use of standards in developing and implementing protocols ensures

that products from different manufacturers can work together for efficient

communications.


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Physical Components of a network

Devices that extend the range of a network by receiving data on one

port, and then regenerating the data and sending it out to all other

ports.

This process means that all traffic from a device connected to the hub

is sent to all the other devices connected to the hub every time the hub

transmits data.

This causes a great amount of network traffic.

Internal Bus Topology

UPLINK Port


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A typical bridge have just two ports, linking two segments of the same

network.

A bridge is a device used to filter network traffic between LAN

segments.

Bridges keep a record of all the devices on each segment to which the

bridge is connected.

When the bridge receives a frame, the destination address is examined

by the bridge to determine if the frame is to be sent to a differentsegment, or dropped.

The bridge also helps to improve the flow of data by keeping frames

confined to only the segment to which the frame belongs


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Switches :

multiport bridges.

A switch has several ports, depending on how many network segments

are to be linked.

A switch is a more sophisticated device than a bridge.

A switch maintains a table of the MAC addresses for computers that are

connected to each port.

Switches use MAC addresses to forward a frame within a single network.

When a frame arrives at a port, the switch compares the address

information in the frame to its MAC address table. The switch then

determines which port to use to forward the frame.


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Routers :

Devices that connect entire networks to each other.

Routers use IP addresses to forward frames to other networks.

Routers contain tables of IP addresses along with optimal destination

routes to other networks.


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Types of LAN topologies

PhysicalPhysical layout of the components on

the network

Logical

Determines how the hosts

communicate across a medium

Physical Topologies :

Bus Topology

Ring Topology

Star Topology

Hierarchical or Extended Star

Mesh Topology


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Bus Topology :

each computer connects to a common cable. The cable connects one computer to the next

The cable has a small cap installed at the end, called a terminator.

Cheap

Collision (CSMA/CD) Carrier sense multiple access with collision detection

Jamming Signal

BW=10Mb/S

Cable Fault

Host Fault

Cable Length


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Ring Topology :

hosts are connected in a physical ring or circle.

ring topology has no beginning or end, the cable does not need to

be terminated.

A specially-formatted frame, called a token, travels around the ring,

stopping at each host. If a host wants to transmit data, the host adds the data and the

destination address to the frame.

The frame then continues around the ring until

the frame stops at the host with the

destination address. The destination host takes

the data out of the frame.

BW=45Mb/s

Expensive (NIC)

Cable Fault

Host Fault/OFF


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Star Topology :

The star topology has a central connection point

which is normally a device such as a hub, switch, or router.

Each host on a network has a cable segment that attaches the host

directly to the central connection point.

The advantage of a star topology is that it is easy to troubleshoot. Each

host is connected to the central device with its own wire. If there is a

problem with that cable, only that host is affected. The rest of the

network remains operational.

BW=100 Mb/s Central Point

Less Cost


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Hierarchical or Extended Star Topology : a star network with an additional networking device connected to the main

networking device

a network cable connects to one hub, and then several other hubs connect to

the first hub. Larger networks


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Mesh Topology :

topology connects all devices to each other

When every device is connected to every other device, a failure of

any cable will not affect the network

The mesh topology is used in WANs that interconnect LANs.

Redundant

Cables Cost

Number of NIC ( Cost )


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Logical Topologies

Broadcast TokenBroadcast :

In a broadcast Topology, each host addresses either data to a particular

host or to all hosts connected on a network.

There is no order that the hosts must follow to use the network it is

first come, first served for transmitting data on the network.

Token :

Token passing controls network access by passing an electronic token

sequentially to each host.

When a host receives the token, it can send data on the network. If thehost has no data to send, it passes the token to the next host and the

process repeats itself.

BandwidthThroughput Example : 100 mb/s


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The Interaction of Protocols

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.


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Examples of these protocols are Application Protocol : Hypertext Transfer Protocol

Transport Protocol: Transmission Control Protocol

TCP :Transmission Control Protocol

UDP :User Datagram Protocol

Internetwork Protocol: Internet Protocol (IP , ARP , ICMP )

Network Access Protocols: Data-link management protocols

HTTP : hyper text transfer protocol

FTP : file transfer protocol

TFTP : Trivial file transfer protocol

SMTP : simple mail transfer protocolSNMP : simple network management protocol

(cisco works is a network management product)

TELNET : used to access remote host or router

LPD : line printer daemon


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layered model

There are benefits to using a layered model to describe network protocols

and operations. Using a layered model :

Assists in protocol design, because 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 because products from different vendors can work

together.

Prevents technology or capabilitychanges in one layer from affecting

other layers above and below.

Provides a common language to describe networking functions and

capabilities.


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There are two basic types of networking models

Protocol Models Reference Models

Protocol Models :

A protocol model provides a model that closelymatches the structure

of a particular protocol suite

The TCP/IP model is a protocol model because it describes the

functions that occur at each layer of protocols within the TCP/IP suite.

The TCP/IP model describes the functionality of the protocols thatmake up the TCP/IP protocol suite.

These protocols, which are implemented on both the sending and

receiving hosts, interact to provide end-to-end delivery of applications

over a network


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TCP/IP Layers

Application Layer

Transport Layer

Internet Layer

Network Access Layer


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A complete communication process includes these steps :

1- Creation of data at the Application layer of the originating source end

device

2- Segmentation and encapsulation of data as it passes down the protocol

stack in the source end device

3- Generation of the data onto the media at the Network Access layer of

the stack

4- Transportation of the data through the internetwork, which consists of

media and any intermediary devices

5- Reception of the data at the Network Access layer of the destination

end device

6- Decapsulation and reassembly of the data as it passes up the stack in

the destination device

7- Passing this data to the destination application at the Application layer

of the destination end device


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Protocol Data Unit (PDU) and Encapsulation

As application data is passed down the protocol stack on its way to be

transmitted across the network media, various protocols add

information to it at each level. This is commonly known as the

encapsulation process.

The form that a piece of data takes at any layer is called a Protocol Data

Unit (PDU). During encapsulation

each succeeding layer encapsulates the PDU that it receives from the

layer above in accordance with the protocol being used

At each stage of the process, a PDU has a different name to reflect its

new appearance , the PDUs are named according to the protocols of

the TCP/IP suite.


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Data : The general term for the PDU used at the Application layer

Segment : Transport Layer PDU

Packet : Internetwork Layer PDU

Frame : Network Access Layer PDU

Bits : A PDU used when physically transmitting data over the medium


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Sending and Receiving Processing

When sending messages on a network, the protocol stack on a hostoperates from top to bottom

In the web server example, we can use the TCP/IP model to illustrate the

process of sending an HTML web page to a client.

The Application layer protocol, HTTP, begins the process by delivering theHTML formatted web page data to the Transport layer.

There the application data is broken into TCP segments. Each TCP segment

is given a label, called a header, containing information about which

process running on the destination to enable the destination process to

reassemble the data back to its original format.


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The Transport layer encapsulates the web page HTML data within

the segment and sends it to the Internet layer, where the IP protocol

is implemented. Here the entire TCP segment is encapsulated withinan IP packet, which adds another label, called the IP header. The IP

header contains source and destination host IP addresses, as well as

information necessary to deliver the packet to its corresponding

destination process.

The IP packet is sent to the Network Access layer Ethernet protocolwhere it is encapsulated within a frame header and trailer. Each

frame header contains a source and destination physical address.

The physical address uniquelyidentifies the devices on the local

network. The trailer contains error checking information. Finally the

bits are encoded onto the Ethernet media by the server NIC.

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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Reference Models :

A reference model provides a common reference for maintaining

consistency within all types of network protocols and services.

The primary purpose of a reference model is to aid in clearer

understanding of the functions and process involved.

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

internetwork reference model.

It is used for data network design, operation specifications, and

troubleshooting.


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Application Layer

PresentationLayer

SessionLayer

TransportLayer

NetworkLayer

DatalinkLayer

PhysicalLayer

THE Open Systems Interconnection (OSI) Model


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Getting the data to the end device

During the process of encapsulation, address identifiers are added to

the data as it travels down the protocol stack on the source host.

there are multiple layers of protocols that prepare the data for

transmission to its destination.

there are multiple layers of addressing to ensure its delivery.


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The Layer 2 address is unique on the local network and represents the address of

the end device on the physical media. In a LAN using Ethernet

this address is called the Media Access Control (MAC) address.

When two end devices communicate on the local Ethernet network the frames that

are exchanged between them contain the destination and source MAC addresses.

Once a frame is successfully received by the destination host, the Layer 2 addressinformation is removed as the data is decapsulated and moved up the protocol

stack to Layer 3.

Layer 2 addresses are only used to communicate between devices on a single local

network

DatalinkLayer : (Layer 2)

Layer 2 PDU called a frame

Layer 2 is concerned with the delivery of messages on a single local network.

the host physical address, is contained in the header of the Layer 2 PDU,


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Network Layer : (Layer 3)

designed to move data from one local network to another local networkwithin an internetwork.

Layer 3 addresses must include identifiers that enable intermediary

network devices to locate hosts on different networks.

IP host address contains information about the network where the host islocated.

At the boundary of each local network, an intermediary network device,

usually a router.

Router decapsulates the frame to read the destination host address

contained in the header of the packet


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Routers use the network identifier portion of this address to determine

which path to use to reach the destination host.

Once the path is determined, the router encapsulates the packet in a new

frame and sends it on its way toward the destination end device.

When the frame reaches its final destination, the frame and packet headers

are removed and the data moved up to Layer 4.

every IP host address contains information about the network where the

host is located.


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Transport Layer : (Layer 4)

information contained in the PDU header does not identify a destinationhost or a destination network.

What it does identify is the specific process or service running on the

destination host device that will act on the data being delivered.

Hosts, whether they are clients or servers on the Internet, can runmultiple network applications simultaneously. People using PCs often

have an e-mail client running at the same time as a web browser, an

instant messaging program, some streaming media, and perhaps even a

game. All these separately running programs are examples of individual

processes.

Think about a computer that has only one network interface on it. All the

data streams created by the applications that are running on the PC

enter and leave through that one interface.

Each application or service is represented at Layer 4 by a port number.


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Application Layer Functionality and Protocols

The Application layer, Layer seven

The top layer of both the OSI and TCP/IP models

the interface between the applications we use to communicate and the

underlying network over which our messages are transmitted.

Application layer protocols are used to exchange data between programs

running on the source and destination hosts.

Provide the human interface to the underlying network


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Presentation Layer

The Presentation layer has three primary Functions:

1- Coding and conversion of Application layer data to ensure that data from the

source device can be interpreted by the appropriate application on the

destination device.

2- Compression of the data in a manner that can be decompressed by the

destination device.

3- Encryption of the data for transmission and the decryption of data upon

receipt by the destination.


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Session Layer

create and maintain dialogs between source and destination applications.

The Session layer 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.


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Network-Aware Applications :

Applications are the software programs used by people to

communicate over the network.

Some end-user applications are network-aware, meaning that theyimplement the Application layer protocols and are able to

communicate directly with the lower layers of the protocol stack.

Web browsers are examples of these types of applications.


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Application layer Services :

Other programs may need the assistance of Application layer services to

use network resources

While applications provide people with a way to create messagesand Application layer services establish an interface to the

network, protocols provide the rules and formats that govern

how data is treated.

Transport layer uses an addressing scheme called a port number.Port numbers identify applications and Application layer services

that are the source and destination of data


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Application layer protocols are

Application layer protocols are used by both the source and

destination devices during a communication session.

the Application layer protocols implemented on the source and

destination host must match.

Protocols specify :

how data inside the messages is structured

the types of messages that are sent between source and

destination.

These messages can be requests for services, acknowledgments,

data messages, status messages, or error messages.

Protocols also define message dialogues, ensuring that a

message being sent is met by the expected response and the

correct services are invoked when data transfer occurs.


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the client/server model

In the client/server model, the 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.

Application layer protocols describe the format of the requests and

responses between clients and servers.

Data transfer from a client to a server is referred to as an upload and

data from a server to a client as a download.


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Server :

any device that responds to requests from client applications isfunctioning as a server.

A server is usually a computer that contains information to be shared

with many client systems

a Server Daemon :

the server runs a service, or process, sometimes called a serverdaemon

daemons typically run in the background and are not under an end

user's direct control.

because they are programmed to respond whenever the serverreceives a request for the service provided by the daemon.

When a daemon "hears" a request from a client, it exchanges

appropriate messages with the client, as required by its protocol, and

proceeds to send the requested data to the client in the proper

format.


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Peer to peer networking and applications (p2p) model Two or more computers are connected via a network and can share

resources (such as printers and files) without having a dedicated server.

Each person can set his or her computer to share files, enable

networked games, or share an Internet connection

Information can be located anywhere on any connected device.

Most of the current operating systems support file and print sharing

without requiring additional server software.

User accounts and access rights must be set individually on each peer

device.

Gnutella Protocol


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Domain Name System (DNS)

In data networks, devices are labeled with numeric IP addressesDomain names were created to convert the numeric address into a simple,

recognizable name.

www.cisco.com, are much easier for people to remember than

198.133.219.25, which is the actual numeric address for this server.

The Domain Name System (DNS) was created for domain name to

address resolution for these networks.

DNS is a client/server service

The DNS protocol defines an automated service that matches resourcenames with the required numeric network address.

Computer operating systems also have a utility called nslookup that

allows the user to manually query the name servers to resolve a given

host name.


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Hypertext Transfer Protocol (HTTP)

When a web address (or URL) is typed into a web browser, the web

browser establishes a connection to the web service running on the

server using the HTTP protocol.

For this example, we will use the URL: http://www.cisco.com/web-

server.htm.

1. http (the protocol )

2. www.cisco.com (the server name)

3. web-server.htm (the specific file name requested).

The Hypertext Transfer Protocol (HTTP), one of the protocols in theTCP/IP suite, was originally developed to publish and retrieve HTML

pages


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E-mail Services and SMTP/POP Protocols

When people compose e-mail messages, they typically use an application

called a Mail User Agent(MUA)

The MUA allows messages to be sent and places received messages into

the client's mailbox

In order to receive e-mail messages from an e-mail server, the e-mail client

can use POP

Sending e-mail from either a client or a server uses message formats and

command strings defined by the SMTP protocol.


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E-mail Server Processes - MTA and MDA

The e-mail server operates two separate processes:

- Mail Transfer Agent (MTA)

- Mail Delivery Agent (MDA)

The Mail Transfer Agent (MTA) process is used to forward e-mail.

the MTA receives messages from the MUA or from another MTA on

another e-mail server. Based on the message header

1 - If the mail is addressed to a user whose mailbox is on the local server, the

mail is passed to the MDA.

2- If the mail is for a user not on the local server, the MTA routes the e-mail

to the MTA on the appropriate server.


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File Transfer Protocol (FTP)

Application layer protocol.

FTP allow file transfers between a client and a server.

An FTP client is an application that runs on a computer that is used to

push and pull files from a server running

FTP requires two connections between the client and the server: one for

commands and replies, the other for the actual file transfer.


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Dynamic Host Configuration Protocol (DHCP)This is the IP address information that a DHCP server can assign to hosts:

1- IP address

2- Subnet mask

3- Default gateway

DHCP allows a host to obtain an IP address dynamically when it connects

to the network.

The DHCP server is contacted and an address requested. The DHCP server

chooses an address from a configured range of addresses called a pooland assigns ("leases") it to the host for a set period.

DHCP distributed addresses are not permanently assigned to hosts but

are only leased for a period of time. If the host is powered down or taken

off the network, the address is returned to the pool for reuse. This is

especially helpful with mobile users that come and go on a network.


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When a DHCP-configured device boots up or connects to the network, the client

broadcasts a DHCP DISCOVER packet to identify any available DHCP servers on

the network.

A DHCP server replies with a DHCP OFFER, which is a lease offer message with

an assigned IP address, subnet mask, DNS server, and default gateway

information as well as the duration of the lease.

The client may receive multiple DHCP OFFER packets if there is more than one

DHCP server on the local network,

so it must choose between them, and broadcast a DHCP REQUEST packet that

identifies the explicit server and lease offer that the client is accepting.

Assuming that the IP address requested by the client, or offered by the server, is

still valid, the server would return a DHCP ACK message that acknowledges to

the client the lease is finalized.


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If the offer is no longer valid - perhaps due to a time-out or another

client allocating the lease - then the selected server will respond with a

DHCP NAK message (Negative Acknowledgement).

If a DHCP NAK message is returned, then the selection process must

begin again with a new DHCP DISCOVER message being transmitted.

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