Transport Layer Comprehensive Notes textbook

Chapter 13: Introduction to the Transport Layer

Objectives of the Transport Layer

• Process-to-Process Communication: Understand the difference between process-to-process and host-to-host communication.
• Addressing: Discuss the addressing mechanism at the transport layer, focusing on port numbers and their purposes.
• Packetizing: Explain encapsulation and decapsulation of messages.
• Multiplexing & Demultiplexing: Discuss services like multiplexing (many-to-one) and demultiplexing (one-to-many).
• Flow Control: Explore how flow control can be managed at the transport layer.
• Error Control: Discuss methods for error control at the transport layer.
• Congestion Control: Understand how congestion control is implemented.
• Connection Services: Differentiate between connectionless and connection-oriented services using Finite State Machines (FSMs).
• Transport Protocols: Describe behaviors of four generic transport-layer protocols: simple, Stop-and-Wait, Go-Back-N, and Selective-Repeat protocols.
• Bidirectional Communication: Understand the concept of bidirectional communication through piggybacking.

Transport-Layer Services

• Layer Position: The transport layer operates between the network layer and the application layer, providing services to applications and utilizing services from the network layer.
• Services Offered: Includes addressing, flow control, error control, and congestion control.

Process-to-Process Communication vs. Host-to-Host Communication

• Transport Layers: Implementation ensures processes on hosts can communicate effectively.
• Figures: Figure of network vs. transport layer shows how processes are managed.

Port Numbers

• Types of Port Numbers:
  • Well-Known Ports: 0 through 1,023, assigned to specific protocols/services.
  • Registered Ports: 1,024 to 49,151, registered with IANA for specific applications.
  • Dynamic/Private Ports: 49,152 to 65,535 for non-registered applications.
• Usage in UNIX: Well-known ports stored in /etc/services file, can be queried for application ports (e.g., TFTP on port 69).

Encapsulation and Decapsulation

• Encapsulation Process: The process of adding headers to data as it moves down the protocol stack.
• Decapsulation Process: The reverse process as data ascends through the protocol stack.

Multiplexing and Demultiplexing

• Multiplexing: The process where multiple applications can send their data over a single transport channel.
• Demultiplexing: On the receiving side, separating the data back to the original applications.

Flow Control

• Concept: Controls the rate of data transmission between sender and receiver.
• Techniques:
  • Single-slot buffering was discussed for its inefficiency.
  • Concepts of pushing vs. pulling data during transmission.

Error Control

• Mechanisms: Use of sequence numbers for packets and acknowledgment to ensure data integrity.
• Protocol Examples: Different methods can be employed based on the protocol being used (e.g., Stop-and-Wait, Go-Back-N, Selective-Repeat).

Congestion Control

• Definition: Techniques used to control network traffic that can lead to congestion.

Connection-Oriented vs Connectionless Services

• Connection-Oriented Services: Establishes a connection before transmitting data. Includes extensive acknowledgment systems.
• Connectionless Services: Data is sent without establishing a connection, with simple packet delivery techniques.

Overview of Transport-Layer Protocols

• Transport Protocol Types:
  • Simple Protocol: No flow or error control; meant for basic communication.
  • Stop-and-Wait Protocol: Uses acknowledgment for received packets; packets can be resent on errors.
  • Go-Back-N Protocol: Handles multiple packets but requires retransmission of all outstanding packets when an error occurs.
  • Selective-Repeat Protocol: Resends only lost packets based on arrived acknowledgments, efficient in error recovery.

Bidirectional Protocols and Piggybacking

• Concept: Allows data to be sent back and forth using the same channel efficiently by attaching acknowledgments to the data packets being sent back.

Examples and Figures

• Numerous figures illustrate flow control, error control, encapsulation, and the functioning of different transport-layer protocols.

Conclusion

• Understanding the transport layer is crucial for efficient data communication and management across networks. Different protocols serve varied networking needs, incorporating methods for control, reliability, and effective data packet management.