Understanding the Internet Infrastructure

Chapter 3: Transport Layer

• The transport layer provides logical communication between application processes running on different hosts.
• Transport protocols run in end systems, breaking application messages into segments, and passing them to the network layer.
• The receiver reassembles segments into messages and passes them to the application layer.
• Multiple transport protocols are available to applications, including TCP and UDP.

Transport Layer Services

• Transport layer services provide:
  • Multiplexing and demultiplexing
  • Reliable data transfer
  • Flow control
  • Congestion control

Multiplexing and Demultiplexing

• Multiplexing: combining multiple application messages into a single transport layer segment
• Demultiplexing: extracting multiple application messages from a single transport layer segment

Connectionless Transport: UDP

• UDP (User Datagram Protocol) is a connectionless transport protocol.
• UDP provides no guarantee of delivery or order of packets.

Principles of Reliable Data Transfer

• Reliable data transfer involves error detection and correction.
• Error detection uses checksums to detect bit errors.
• Receiver feedback (ACKs and NAKs) is used to recover from errors.

RDT 2.0: A Reliable Data Transfer Protocol

• RDT 2.0 is a reliable data transfer protocol that uses error detection and receiver feedback.
• The protocol uses ACKs and NAKs to recover from errors.
• RDT 2.0 has a fatal flaw, manifesting as lost packets and long delays.

Connection-Oriented Transport: TCP

• TCP (Transmission Control Protocol) is a connection-oriented transport protocol.
• TCP provides reliable data transfer and guarantees delivery and order of packets.
• TCP segment structure includes a header and data.
• TCP provides flow control and congestion control.

TCP Congestion Control

• TCP congestion control regulates the amount of data sent to prevent network congestion.
• Causes of congestion include:
  • Lost packets (buffer overflow at routers)
  • Long delays (queueing in router buffers)
• Costs of congestion include:
  • Decreased goodput
  • Unneeded retransmissions

Principles of Congestion Control

• Congestion control involves regulating the amount of data sent to prevent network congestion.
• Congestion control scenarios include:
  • Scenario 1: unlimited shared output link buffers
  • Scenario 2: one router, finite buffers
  • Scenario 3: four senders, multihop paths

Note: These study notes focus on the key concepts and ideas presented in the text, and are organized to facilitate easy review and understanding of the material.

Introduction to C++

• C++ program consists of several parts, including comments, preprocessor directives, and functions.

The Parts of a C++ Program

• A C++ program can have comments, which start with // and are ignored by the compiler.
• The #include directive is a preprocessor directive that tells the compiler to include a file.
• The using namespace std; statement specifies which namespace to use.
• The int main() function is the entry point of the program, where execution begins.
• The {} block is used to group statements together in a function.

C++ Program Structure

• A C++ program typically includes a main function, which is the starting point of the program.
• The main function contains a block of code, which is enclosed in {}.

Explore the fundamental components of the Internet from a 'nuts and bolts' perspective, including PC servers, wireless laptops, routers, and network applications. Learn about the concept of hosts, global ISPs, communication through wired and wireless links, and the role of packet router switches.