Post on 26-May-2015
transcript
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Sub-Topic : Features of TCP (Part-2)
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Recap
In the previous topic , you have learnt about
• Layers of TCP/IP protocol
• Role of transport layer in TCP/IP protocol
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Objectives
On completion of this topic, you would be able to know about
• List out the features supported by TCP
• Understand features of TCP
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TCP - Features
• Numbering System
• Byte Number
• Sequence Number
• Acknowledgement Number
• Reliable transfer of data
• Flow Control
• Error Control
• Congestion Control
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TCP – Features ( Contd…)
• Inter-operability
• Flexibility
• Multi-Vendor Support
• Window Based Protocol
• Connection oriented service
• Full duplex data transfer
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TCP – Numbering System
• TCP keeps track of the segments being transmitted or
received by assigning numbers
• Byte Number assigned to data bytes to be transferred
• Sequence Number to Segments
• Acknowledgement Number to Received segments
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Byte Number
• Used for Flow Control and Error Control
• All data bytes transmitted in each connection are numbered by the TCP
• Numbering starts with a randomly generated number
• Numbering is independent in each direction
• TCP stores the received data bytes in a sending buffer and numbers them
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Sequence Number
• TCP assigns a Sequence number to each segment transmitted
• Sequence Number is the first byte number carried in that segment
Sequence Number is assigned when• Segment carries both data and control information
( Piggy backing )
• Segment without data, no sequence number
• Example : if x Sequence Number x+1 First Byte Number
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Acknowledgement Number
• Indicates number of the next byte that the
receiver expects to receive
• Acknowledgement number is cumulative
• Confirmation to received data bytes
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TCP – Reliable Transfer of Data
• Ordered data transfer - the destination host rearranges according to sequence number
• Retransmission of lost packets - any cumulative stream not acknowledged will be retransmitted
• Discarding duplicate packets• Error-free data transfer
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HostClient
Send Packet 1Start Timer
Retransmit Packet1Start Timer
Packet should arrive ACK should be sent
ACK would normallyArrive at this time
Receive Packet 1Send ACK 1
Time Expires
Receive ACK 1Cancel Timer
Data PacketTimer
Timer
Fig.4
TCP – Reliable Transfer of Data
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TCP – Flow Control
• limits the rate a sender transfers data to guarantee reliable delivery
• The receiver continually hints the sender on how much data can be received (controlled by the sliding window)
• When the receiving host's buffer fills, the next acknowledgment contains a 0 in the window size, to stop transfer and allow the data in the buffer to be processed
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TCP – Error Control• TCP implements an error control mechanism for
reliable data transfer
• Error Control is byte – oriented
• Segments are checked for error detection
• Error Control includes detecting
• Corrupted Segments and Lost Segments
• Out-of-Order Segments
• Duplicated Segments
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• Error detection & Correction is achieved by
– Check Sum
– Acknowledgement Numbers
– Time-outs
TCP – Error Control
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TCP – Congestion Control
• TCP takes in to account the level of Congestion
in the network
• Congestion level determines the amount of
data sent by a sender
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TCP - Interoperability
• TCP has become the Industry standard
• It supports interoperability across networks
• TCP – A frame work used to develop• complete range of computer communication
standards
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TCP – Flexibility
• TCP allows a variety of implementations
Multi-Vendor Support
• TCP is supported by almost all network software
• Widely used transport layer protocol
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Summary
In this class, you have learnt about
• TCP is a widely used transport layer protocol
• TCP provides process to process, full duplex and connection oriented services
• The main features supported by TCP are
• Segment Numbering System
• Flow Control
• Error Control
• Congestion Control
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Summary
In this topic, you have learnt about
• Basic unit of data transfer using TCP is Segment
• TCP uses flow control implemented as a sliding window mechanism
• Data bytes being transferred in each connection are numbered by TCP
• Numbering starts with a randomly generated number
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Summary
TCP uses error control to provide reliable service. Error Control is handled by
• checksum, acknowledgement and time-outs
• Duplicated segments are discarded and Corrupted & lost segments are retransmitted
• Data arrived out of order are temporarily stored by receiving TCP
• TCP guarantees that no out of order segment is delivered to the process
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Quiz
1. TCP is a ____________ layer protocol
A. Application
B. Transport
C. Network
D. Physical
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Quiz
2. Which of the following features are supported by TCP ?
A. Congestion Control
B. Error Control
C. Flow Control
D. All The Above
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Frequently Asked Questions
1. Name the protocols used in the Transport Layer of the TCP/IP protocol suite
2. What is the purpose of TCP ?
3. List the features of TCP
4. Explain about the various features supported by TCP
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3.24 DIFFERENT LAYERS OF TCP/IP