The Saigon CTT Semester 1 CHAPTER 12 – 13 – 14 Le Chi Trung.

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Semester 1Semester 1

CHAPTER 12 – 13 – 14 CHAPTER 12 – 13 – 14

Le Chi TrungLe Chi Trung

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ContentContent

• Transport layer

• TCP and UDP

• Session layer

• Presentation layer

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ScheduleSchedule

No Name Est time No Name05-Jul 12.1 The transport layer 0:15:00

12.2 TCP and UTP 0:15:0012.3 TCP connection methods 0:30:00

12.1.3 Protocol Inspector and TCP13.1 The basics of the session layer 0:15:0014.1 The basics of the presentation layer 0:15:00

07-Jul Chapter 12 + 13 + 14 Online Exam

Lesson LabDay

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TRANSPORT LAYERTRANSPORT LAYER

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Why we need a transport layer?Why we need a transport layer?

• Layer 1 allows bit streams to be created and to travel.

• Layer 2 packages those data packets into frames to be converted to bit streams and makes data-link delivery possible.

• Layer 3 packages data from upper layers in packets and makes routing and network delivery possible.

But they made no provision for assuring our data reliably

travels end-to-end across the often vast network path.

But they made no provision for assuring our data reliably

travels end-to-end across the often vast network path.

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Purpose of the transport layerPurpose of the transport layer

• Transport and regulate the flow of information from source to destination, reliably and accurately.

• The end-to-end control: – Sliding windows.

– Sequencing numbers.

– Acknowledgments.

– Segmentation.

– Multiplexing.

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TCP and UDPTCP and UDP

• The emphasis of this curriculum is on TCP/IP Ethernet networks.

• The TCP/IP protocol of the OSI model Layer 4 (transport layer) has two protocols - TCP and UDP.

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TCP/IPTCP/IP

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PortPort

• Both TCP and UDP use port (or socket) numbers to pass information to the upper layers.

RFC-1700

RFC-1700

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Range of portsRange of ports

• 2 bytes: 0 – 65535.– Numbers below 255 : for public applications.– Numbers from 255 - 1023 : assigned to

companies for marketable applications.– Numbers above 1023 : are unregulated.

• End systems use port numbers to select proper applications.

• Originating source port numbers are dynamically assigned by the source host; usually, it is a number larger than 1023.

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Telnet port numberTelnet port number

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TCP AND UDPTCP AND UDP

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TCPTCP

• TCP supplies a virtual circuit between end-user applications. These are its characteristics:– connection-oriented.– reliable.– divides outgoing messages into segments.– reassembles messages at the destination

station.– re-sends anything not received.– reassembles messages from incoming

segments.

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TCP Header formatTCP Header format

• Protocol that provides reliable full-duplex data transmission.

RFC-761

RFC-761

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TCP Header format:TCP Header format: Port number Port number

• Source Port 16 bits.

• Destination Port 16 bits.

• Source Port 16 bits.

• Destination Port 16 bits.

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TCP Header format: TCP Header format: SequenceSequence

• Sequence Number: 32 bits– The sequence number of the

first data octet in this segment (except when SYN is present).

• Sequence Number: 32 bits– The sequence number of the

first data octet in this segment (except when SYN is present).

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TCP Header format: TCP Header format: AcknowledgmentAcknowledgment

• Acknowledgment Number: 32 bits– This field contains the value of the

next sequence number the sender of the segment is expecting to receive.

• Acknowledgment Number: 32 bits– This field contains the value of the

next sequence number the sender of the segment is expecting to receive.

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TCP Header format: TCP Header format: Code bitsCode bits

• Control Bits: 8 bits – ACK: Acknowledgment field significant– RST: Reset the connection– SYN: Synchronize sequence numbers– FIN: No more data from sender

• Control Bits: 8 bits – ACK: Acknowledgment field significant– RST: Reset the connection– SYN: Synchronize sequence numbers– FIN: No more data from sender

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TCP Header format: TCP Header format: WindowWindow

• Window: 16 bits– The number of data octets beginning

with the one indicated in the acknowledgment field which the sender of this segment is willing to accept.

• Window: 16 bits– The number of data octets beginning

with the one indicated in the acknowledgment field which the sender of this segment is willing to accept.

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TCP: TCP: Three way handshakingThree way handshaking

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TCP: TCP: Simple acknowledgmentSimple acknowledgment

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TCP: TCP: Sliding acknowledgmentSliding acknowledgment

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TCP: TCP: Sequence and acknowledgmentSequence and acknowledgment

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UDPUDP

• UDP transports data unreliably between hosts. Following are the characteristics:– Connectionless.

– Unreliable.

– Transmit messages (called user datagrams).

– Provides no software checking for message delivery (unreliable).

– Does not reassemble incoming messages.

– Uses no acknowledgements.

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UDP Header formatUDP Header format

• UDP is a simple protocol that exchanges datagrams, without acknowledgments or guaranteed delivery.

RFC-768

RFC-768

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Preparation for LABPreparation for LAB

• Lab companion:

– 12.4.1

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ReviewReview

• Transport layer regulates information flow to ensure end-to-end connectivity between host applications reliably and accurately.

• TCP and UDP port numbers.

• Three way handshaking and sliding windows.

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SESSION LAYERSESSION LAYER

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FunctionsFunctions

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ProcessProcess

• Dialog control:– In the conversation, each host plays dual

roles: requesting service and replying with service. Dialogue control determining which role they are playing at any given moment.

– Agree a set of guidelines to use during the communicating with each other.

• Dialog separation:– Order to Initiate, terminate and manage of

communication.

– Using a checkpoint to synchronize.

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Dialog controlDialog control

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Dialog separationDialog separation

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Session layer protocolsSession layer protocols

Discussi

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Discussi

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ReviewReview

• Communication sessions consist of mini-conversations that occur between applications located in different network devices.

• Dialog control.

• Dialog separation.

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PRESENTATION LAYERPRESENTATION LAYER

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FunctionsFunctions

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Three main functionsThree main functions

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Data formattingData formatting

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Data encryptionData encryption

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Data compressionData compression

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ReviewReview

• Determines how graphic images, sound and movies are presented. .

• Provides encryption of data.

• Compresses text and converts graphic images into bit streams so they can be transmitted across a network.

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