Chapter 9: Transport Layer

Chapter 9: Transport Layer

1. Role of the Transport Layer

   • The transport layer is responsible for establishing a temporary communication session between two applications and delivering data between them

2. Transport Layer Responsibilities

   • Tracking Individual Conversations
     • At the transport layer, each set of data flowing between a source application and a destination application is known as a conversation.
   • Segmenting Data and Reassembling Segments
     • Data must be prepared to be sent across the media in manageable pieces
   • Identifying the Applications
     • To pass data streams to the proper applications, the transport layer must identify the target application

3. Conversation Multiplexing

   • To identify each segment of data, the transport layer adds a header containing binary data organized into several fields.

4. Transport Layer Reliability

   • The transport layer is also responsible for managing reliability requirements of a conversation.

5. TCP

   • TCP transport is analogous to sending packages that are tracked from source to destination

6. UDP

   • provides the basic functions for delivering data segments between the appropriate applications, with very little overhead and data checking.

7. TCP Features

   • Flow Control
     • it can request that the sending application reduce the rate of data flow.
   • Same-Order Delivery
     • TCP can ensure that these segments are reassembled into the proper order.
   • Reliable Delivery
     • reliability means ensuring that each segment that the source sends arrives at the destination.
   • Establishing a Session
     • TCP is a connection-oriented protocol.

8. TCP Header

   • TCP is a stateful protocol.
     • A stateful protocol is a protocol that keeps track of the state of the communication session

9. UDP Features

   • User Datagram Protocol (UDP) is considered a best-effort transport protocol.

10. Multiple Separate Conversations

    • The transport layer must be able to separate and manage multiple communications

11. Port Numbers

    • Source Port
      • is dynamically generated by the sending device to identify a conversation between two devices.
    • Destination Port
      • The client places a destination port number in the segment

12. Socket Pairs

    • The source and destination ports are placed within the segment.

13. Port Number Groups

    • Well-known Ports (Numbers 0 to 1023)
    • Registered Ports (Numbers 1024 to 49151)
    • Dynamic or Private Ports (Numbers 49152 to 65535)

14. TCP Connection Establishment

    • the host client establishes the connection with the server.

15. TCP Session Termination

    • To close a connection, the Finish (FIN) control flag must be set in the segment header.

16. TCP Three-way Handshake Analysis

    • Establishes that the destination device is present on the network
    • Verifies that the destination device has an active service
    • Informs the destination device that the source intends to establish a communication

17. TCP Reliability - Ordered Delivery

    • TCP segments may arrive at their destination out of order.

18. TCP Flow Control - Window Size and Acknowledgments

    • TCP also provides mechanisms for flow control, the amount of data that the destination can receive and process reliably.

19. UDP Low Overhead versus Reliability

    • UDP is a simple protocol that provides the basic transport layer functions.