1. Transport Layer
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2. TRANSPORT LAYER SERVICES TO UPPER LAYER
To provide efficient, reliable, and cost-effective service to its users.
It takes help of the services provided by the network layer.
The hardware and/or software within the transport layer that does the work is called the transport entity.
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3. Services Provided to the Upper Layers
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4. Transport Protocol Data Unit
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5. The transport layer is responsible for process-to-process delivery.
Note
The transport layer is responsible for process-to-process delivery.
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6. Types of data deliveries
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7. Port numbers
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8. IP addresses versus port numbers
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9. IANA ranges
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10. The Internet Transport Protocol
Connectionless–UDP
Connection oriented -TCP
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11. Position of UDP and TCP in TCP/IP suite
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12. Dec 2007
Why does UDP exist ? Would it not have been enough to just let user processes send raw IP packet ? [8 Marks]
Compare and contrast between RPC and UDP [8 Marks]
Dec 2009
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13. USER DATAGRAM PROTOCOL (UDP)
Connectionless
Unreliable
Very limited error checking
No flow control and acknowledgement mechanism
Simple protocol with minimum overhead
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14. User datagram header format
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15. Source n Destination Port Numbers
If destination host is a client, the port number in most cases is ephemeral port number.
If destination host is the server, the port number in most cases, is a well-known port.
It is 16 bit long, which means that port number can range from 0 to 65,535.
This is the port number used by the process running on source host.
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16. UDP Length
The 16 bit can define total length of 0 to 65,535 bytes. However the total length needs to be much less because an UDP user datagram is stored in an IP datagram with the total length of bytes.
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17. UDP length = IP length – IP header’s length
Note
UDP length = IP length – IP header’s length
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18. UDP Checksum
This field is used to detect errors over the entire user datagram (header + data).
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19. Transmission Control Protocol
Connection oriented.
Reliable.
Sends encapsulated IP packets by establishing a connection.
Uses flow and error control mechanisms.
Helps in process to process communication.
Implements a congestion-control mechanism.
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20. Stream delivery
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21. Sending and receiving buffers
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22. TCP Header Format
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23. Flags
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24. Flags…
URG is set to 1 if the Urgent pointer field is in use. The Urgent pointer is used to indicate a byte offset from the current sequence number at which urgent data are to be found.
The ACK bit is set to 1 to indicate that the Acknowledgement number is valid. If ACK is 0, the segment does not contain an acknowledgement so the Acknowledgement number field is ignored.
The PSH bit indicates PUSHed data. This bit requests the receiver to deliver the data to the application upon arrival and not store the data in the buffer until a full buffer signal has been received.
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25. Flags…
The RST bit is used to reset a connection that has become confused due to a host crash or some other reason. In general, if you get a segment with the RST bit on, you have a problem in your hands.
SYN bit is used to synchronize sequence numbers. Only the first packet sent from each end should have this flag set.
The FIN bit is used to release a connection. It specifies that the sender has no more data to transmit.
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26. TCP Vs UDP
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27. TCP Connection Connection Establishment Data Transfer
Connection Termination
Connection Reset
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28. Connection establishment using three-way handshaking
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29. Note
SYN segment cannot carry data, but it consumes one sequence number.
SYN + ACK segment cannot carry data, but does consume one sequence number.
An ACK segment, if carrying no data, consumes no sequence number.
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30. Data Transfer
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31. The FIN segment consumes one sequence number if it does not carry data
Note
The FIN segment consumes one sequence number if it does not carry data
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32. Connection termination using three-way handshaking
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33. State Transition Diagram
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