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"21 3 $ 4 5 6 7 89:; ? @ A B C D EF E G H IKJ L M N O

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Page 1: "21 3 $ 4 5 6 7 89:; ? @ A B C D EF E G H IKJ L M N O

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Page 8: "21 3 $ 4 5 6 7 89:; ? @ A B C D EF E G H IKJ L M N O

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Page 9: "21 3 $ 4 5 6 7 89:; ? @ A B C D EF E G H IKJ L M N O

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Page 10: "21 3 $ 4 5 6 7 89:; ? @ A B C D EF E G H IKJ L M N O

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IRTF : Internet Research Task ForceIESG : Internet Engineering Steering Group

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Page 12: "21 3 $ 4 5 6 7 89:; ? @ A B C D EF E G H IKJ L M N O

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Page 13: "21 3 $ 4 5 6 7 89:; ? @ A B C D EF E G H IKJ L M N O

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Page 14: "21 3 $ 4 5 6 7 89:; ? @ A B C D EF E G H IKJ L M N O

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Page 16: "21 3 $ 4 5 6 7 89:; ? @ A B C D EF E G H IKJ L M N O

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Page 17: "21 3 $ 4 5 6 7 89:; ? @ A B C D EF E G H IKJ L M N O

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Page 18: "21 3 $ 4 5 6 7 89:; ? @ A B C D EF E G H IKJ L M N O

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Page 19: "21 3 $ 4 5 6 7 89:; ? @ A B C D EF E G H IKJ L M N O

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Page 20: "21 3 $ 4 5 6 7 89:; ? @ A B C D EF E G H IKJ L M N O

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Page 21: "21 3 $ 4 5 6 7 89:; ? @ A B C D EF E G H IKJ L M N O

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Page 22: "21 3 $ 4 5 6 7 89:; ? @ A B C D EF E G H IKJ L M N O

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Page 23: "21 3 $ 4 5 6 7 89:; ? @ A B C D EF E G H IKJ L M N O

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Copper twisted pair

Switch

Switching office

High-bandwidth fiber trunk

Junction box

(a)

(b)

House

High-bandwidth fiber trunk

Copper cable TV wire

House

Junction box

Fiber

Fiber

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Router

WAN

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Layer 5

Layer 4

Layer 3

Layer 2

Layer 1

Host 1

Layer 4/5 interface

Layer 3/4 interface

Layer 2/3 interface

Layer 1/2 interface

Layer 5 protocolLayer 5

Layer 4

Layer 3

Layer 2

Layer 1

Host 2

Layer 4 protocol

Layer 3 protocol

Layer 2 protocol

Layer 1 protocol

Physical medium

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I like rabbits

Location A

3

2

1

3

2

1

Location B

Message Philosopher

Translator

Secretary

Information for the remote translator

Information for the remote secretary

L: Dutch Ik hou van konijnen

Fax #--- L: Dutch Ik hou van konijnen

J'aime les

lapins

L: Dutch Ik hou van konijnen

Fax #--- L: Dutch Ik hou van konijnen

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� � � � � � # �� � � � � #� � � � �� " � �H2 H3 H4 M1 T2 H2 H3 M2 T2 H2 H3 H4 M1 T2 H2 H3 M2 T2

H3 H4 M1 H3 M2 H3 H4 M1 H3 M2

H4 M H4 M

M M

Layer 2 protocol

2

Layer 3 protocol

Layer 4 protocol

Layer 5 protocol

3

4

5

1

Layer

Source machine Destination machine

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Layer n+1

Interface

Layer n

ICI SDU

IDU

ICI SDU

SAP

SDU

SAP = Service Access Point IDU = Interface Data Unit SDU = Service Data Unit PDU = Protocol Data Unit ICI = Interface Control Information

Layer n entities exchange n-PDUs in their layer n protocol

Headern-PDU

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Layer

Presentation

Application

Session

Transport

Network

Data link

Physical

7

6

5

4

3

2

1

Interface

Interface

Host A

Name of unit exchanged

APDU

PPDU

SPDU

TPDU

Packet

Frame

Bit

Presentation

Application

Session

Transport

Network

Data link

Physical

Host B

Network Network

Data link Data link

Physical Physical

Router Router

Internal subnet protocol

Application protocol

Presentation protocol

Transport protocol

Session protocol

Communication subnet boundary

Network layer host-router protocol

Data link layer host-router protocolPhysical layer host-router protocol

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TCP/IPOSI

Application

Presentation

Session

Transport

Network

Data link

Physical

7

6

5

4

3

2

1

Application

Transport

Internet

Host-to-network

Not present in the model

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Firmware

Software

OperatingSystem

UserSpace

Hardware

Physical

NetworkAccess

Internet

Application

Transport(host−to−host)

TCP/IP

Application

Presentation

Session

Transport

Network

Data Link

Physical

OSI

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Server

FrameRelay

Network

Router

IEEE 802 LAN

Workstation

Physical

MAC

LLC

IP

Physical

MAC

LLC

IP

Physical

FrameRelay

FrameRelay

TCP

Application

Physical

IP

TCP

Application

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Router J

TCP

IP

Physical Physical

IP

NAP 1 NAP 2

Network AccessProtocol #1

Host A

App XApp Y

TCP

IP

Network AccessProtocol #2

Host B

App YApp X

Network 1 Network 2

Global networkaddress

Subnetwork attachmentpoint address

Logical connection(e.g., virtual circuit)

Logical connection(TCP connection)

Port orservice access point (SAP)

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DataTI

DataT

Data

Physical

IP

TCP

Application

FrameRelay DataTIF F

1. Preparing the data. Theapplication protocol prepares a blockof data for transmission. For example,an email message (SMTP), a file (FTP),or a block of user input (TELNET).

2. Using a common syntax. If necessary,the data are converted to a form expectedby the destination. This may includea different character code, the use ofencryption, and/or compression.

3. Segmenting the data. TCP may breakthe data block into a number of segments,keeping track of their sequence. Each TCPsegment includes a header containing asequence number and a frame check sequence to detect errors.

5. Fragmenting the segments. IP maybreak a TCP segment into a number of datagrams to meet size requirements ofthe intervening networks. Each datagramincludes a header containing a destinationaddress, a frame check sequence, and othercontrol information.

6. Framing. A frame relay header andtrailer is added to each IP datagram. Theheader contains a connection identifier andthe trailer contains a frame check sequence

7. Transmission. Eachframe is transmitted overthe medium as a sequenceof bits.

4. Duplicating segments. A copy is madeof each TCP segment, in case the lossor damage of a segment necessitatesretransmission. When an acknowledgmentis received from the other TCP entity, asegment is erased.

Peer−to−peer dialogue.Before data are sent, thesending and receivingapplications agree on formatand encoding and agree toexchange data.

Peer−to−peer dialogue.The two TCP entities agreeto open a connection.

Peer−to−peer dialogue.Each IP datagram is forwardedthrough networks and routersto the destination system.

Peer−to−peer dialogue.Each frame is forwarded throughthe frame relay network.

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DataTIL

Physical

MACDataTIL#####M ##### MDataTIF F

LLC

FrameRelay

9. Processing the frame. Theframe relay layer removes theheader and trailer and processesthem. The frame check sequence is used for error detection. Theconnection numberidentifies the source.

13. Transmission. Eachframe is transmitted overthe medium as a sequenceof bits.

12. Framing A MAC header andtrailer is added to each LLC PDU,forming a MAC frame. The headercontains address information and thetrailer contains a frame check sequence.

11. Forming LLC PDU. An LLCheader is added to each IP datagramto form an LLC PDU. The headercontains sequence number andaddress information.

8. Arriving at router. Theincoming signal is receivedover the transmission mediumand interpreted as a frame of bits.

DataTI

IP

10. Routing the packet. IP examinesthe IP header and makes a routingdecision. It determines which outgoinglink is to be used and then passesthe datagram back to the link layerfor transmission on that link.

Peer−to−peer dialogue.The router will pass thisdatagram onto anotherrouter or to the destinationsystem.

Physical

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DataTIL

Physical

LLC

IP

TCP

MAC

Data

Application

DataTI

DataT

14. Arriving at destination. The incomingsignal is received over the transmissionmedium and interpreted as a frame of bits.

DataTIL ####M #### M

15. Processing the frame. The MAC layerremoves the header and trailer and processesthem. The frame check sequenceis used for error detection.

16. Processing the LLC PDU. The LLC layerremoves the header and processes it. Thesequence number is used for flow and errorcontrol.

17. Processing the IP datagram. IPremoves the header. The frame checksequence and other controlinformation are processed.

18. Processing the TCP segment. TCPremoves the header. It checks the framecheck sequence and acknowledges if there isa match and discards for mismatch. Flow controlis also performed.

19. Reassembling user data. If TCPhas broken the user data into multiplesegments, these are reassembled and theblock is passed up to the application.

20. Delivering the data. The applicationperforms any needed transformations, includingdecompression and decryption, and directs the data to the appropriate file or other destination.

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& � � #(' ) )* * * ! � � � �� �"! # � � � $ % � � � ),+ � �� � � � � �

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