Understanding the Internet Infrastructure

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What is the function of routers in the Internet?

Routers forward packets of data.

Which component is not part of the 'nuts and bolts' view of the Internet?

Web service

What do ISPs stand for in the context of the Internet?

Internet Service Providers

Which organization is responsible for Internet standards like RFC?


What type of links connect hosts within a home network?

Wired links

What aspect is highlighted in the service view of the Internet?

Sending and receiving app programs

What type of devices are considered as end systems in the 'nuts and bolts' view of the Internet?

PC server and wireless laptop

Which technology is used to control the sending and receiving of messages in the 'network of networks' view of the Internet?

TCP and IP

What is the function of packet router switches in the Internet infrastructure?

Forward chunks of data known as packets

Which organization is responsible for Internet standards like RFC (Request for Comments)?

IETF: Internet Engineering Task Force

What do ISPs provide in the service view of the Internet?

Service options for applications

Which type of links connect hosts within a home network?

Fiber links

What happens if packets are lost due to full buffers at a router in scenario 2?

Sender only resends packets confirmed as lost.

Why does the asymptotic goodput remain at R/2 even when some packets are retransmissions?

The sender only resends packets confirmed as lost.

In scenario 2, what is the consequence of premature timeouts by the sender?

Some packets are retransmitted unnecessarily.

What is a consequence of having duplicates due to premature timeouts in scenario 2?

Decrease in goodput.

How does the number of senders and multihop paths impact congestion in scenario 3?

It leads to more retransmissions.

What is one 'cost' of congestion mentioned in the text related to retransmissions?

Unnecessary retransmissions.

What happens if a sender sends two copies prematurely due to timeout in scenario 2?

Both copies are delivered successfully.

'Goodput' remains at R/2 even if some packets are retransmissions because:

'Goodput' accounts for successful packet deliveries over time.

'Realistic: Duplicates' in scenario 2 refer to:

'Realistic: Duplicates' cause unnecessary retransmissions.

Study Notes

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.

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.

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