AeroLab Reading room

CS / A2 level

Internet structure and network reliability

Protocols manage routing, addressing and end-to-end communication. TCP supports ordered reliable byte streams; IP routes packets without independently guaranteeing their delivery.

Learning objectives

The big idea

Protocols manage routing, addressing and end-to-end communication. TCP supports ordered reliable byte streams; IP routes packets without independently guaranteeing their delivery.

Network design balances redundancy, capacity, cost and security. Circuit and packet switching suit different traffic assumptions; congestion and retransmission can increase delay despite a high nominal link rate.

Worked example

Which protocol provides ordered reliable byte-stream transport: TCP or IP alone?

Follow the solution

TCP manages sequencing and retransmission over the underlying network service.

Investigate and explain

Predict the worked result before calculating. Change one input, record the new result, and explain which assumptions still hold.

Use the prediction activity below; a local model appears only where it supports this topic.

Open the interactive investigation

Check your understanding

1. What is a benefit of redundant network paths?

  1. Guaranteed zero latency
  2. Removal of all security threats
  3. An alternative route if a path fails
Check the answer and reasoning

An alternative route if a path fails

Redundancy can improve resilience while adding cost and complexity.

2. Which protocol provides ordered reliable byte-stream transport: TCP or IP alone?

  1. TCP
  2. IP alone
  3. Neither can ever do so
Check the answer and reasoning

TCP

TCP manages sequencing and retransmission over the underlying network service.

3. Does a fast local link guarantee a fast end-to-end download?

  1. Yes
  2. No
  3. Only on Ethernet
Check the answer and reasoning

No

Other links, congestion, servers and protocol overhead can form bottlenecks.