osi and tcp

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2.1

Figure 2.1 Tasks involved in sending a letter



2.2

2-2 THE OSI MODEL2-2 THE OSI MODEL

Established in 1947, the International Standards Established in 1947, the International Standards

Organization ( Organization ( ISO ISO ) is a multinational body dedicated to ) is a multinational body dedicated toworldwide agreement on international standards !n ISOworldwide agreement on international standards !n ISO

standard that co"ers all as#ects o$ networ%standard that co"ers all as#ects o$ networ%

communications is the O#en Systems Interconnectioncommunications is the O#en Systems Interconnection

( ( OSI OSI ) model It was $irst introduced in the late 197&s ) model It was $irst introduced in the late 197&s

Layered Architecture

Peer-to-Peer Processes

Encapsulation

'o#ics discussed in this section'o

#ics discussed in this section



2.3

I! is the organi"ation.!I is the #odel.

ote



2.$

Figure 2.2 Se"en layers o$ the OSI model



2.%

Figure 2.3 'he interaction between layers in the OSI model



2.&

Figure 2.$ !n e*change using the OSI model



2.'

2-3 LAYERS IN THE OSI MODEL2-3 LAYERS IN THE OSI MODEL

In this section we brie$ly describe the $unctions o$ each In this section we brie$ly describe the $unctions o$ each

layer in the OSI modellayer in the OSI model

Physical Layer

(ata Link Layer

)et*ork Layer

Transport Layer

ession Layer

Presentation Layer

Application Layer

'o#ics discussed in this section'o #ics discussed in this section



2.+

Figure 2.% +hysical layer



• Type of transmission media

• Data rate

•

Topology• Transmission mode

• Synchronization of clock

2.1



2.11

Figure 2.& ata lin% layer



2.12

The data link layer is responsile or #oving

ra#es ro# one hop /node0 to the net.

ote



• Framing

• Physical addressing

•

Flow control• Error control

• Access control

2.13



2.1$

Figure 2.' -o#.to.ho# deli"ery



2.1%

Figure 2.+ etwor% layer



2.1&

The net*ork layer is responsile or thedelivery o individual packets ro#

the source host to the destination host.

ote



• Logical addressing

• Routing

2.1'



2.1+

Figure 2., Source.to.destination deli"ery



2.1,

Figure 2.1 'rans#ort layer



2.2

The transport layer is responsile or the deliveryo a #essage ro# one process to another.

ote



• Serice!point addressing

• Segmentation and reassem"ly

•

#onnection control• Flow control

• Error control

2.21



2.22

Figure 2.11 /eliable #rocess.to.#rocess deli"ery o$ a message



2.23

Figure 2.12 Session layer



2.2$

The session layer is responsile or dialogcontrol and synchroni"ation.

ote



• dialog control (turn to transmit)

• Allow system to either transmitin half duplex or in full duplexmode

• Synchronization (introducingcheck point)

2.2%



2.2&

Figure 2.13 +resentation layer



2.2'

The presentation layer is responsile or translationco#pression and encryption.

ote



• Translation

• Encryption

•

#ompression

2.2+



2.2,

Figure 2.1$ !##lication layer



2.3

The application layer is responsile orproviding services to the user.

ote



• File transfer$ access$ andmanagement%

• &ail serices

2.31



2.32

Figure 2.1% Summary o$ layers

2 4 TCP/IP PROTOCOL SUITE



2.33

2-4 TCP/IP PROTOCOL SUITE2-4 TCP/IP PROTOCOL SUITE

'he layers in the'he layers in the '0+I+ #rotocol suite'0+I+ #rotocol suite do not e*actlydo not e*actly

match those in the OSI model 'he original '0+I+match those in the OSI model 'he original '0+I+ #rotocol suite was de$ined as ha"ing $our layers #rotocol suite was de$ined as ha"ing $our layers host.to.host.to.

networ% networ% , , internet internet , , trans#ort trans#ort , and , and a##licationa##lication -owe"er, -owe"er,

when '0+I+ is com#ared to OSI, we can say that thewhen '0+I+ is com#ared to OSI, we can say that the

'0+I+ #rotocol suite is made o$ $i"e layers'0+I+ #rotocol suite is made o$ $i"e layers #hysical #hysical , ,

data lin% data lin% , , networ% networ% , , trans#ort trans#ort , and , and a##licationa##lication

Physical and (ata Link Layers

)et*ork Layer

Transport Layer

Application Layer




2.3$

Figure 2.1& '0+I+ and OSI model

2 5 ADDRESSING2 5 ADDRESSING



2.3%

2-5 ADDRESSING2-5 ADDRESSING

2our le"els o$ addresses are used in an internet em#loying2our le"els o$ addresses are used in an internet em#loying

the '0+I+ #rotocolsthe '0+I+ #rotocols #hysical #hysical , , logical logical , , #ort #ort , and , and s#eci$ics#eci$ic

Physical Addresses

Logical Addresses

Port Addressespeciic Addresses




2.3&

Figure 2.1' !ddresses in '0+I+



2 3'

Figure 2.1+ /elationshi# o$ layers and addresses in '0+I+

osi and tcp

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