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OCR H446 1.3.3 Internet transfer, packets, IP addresses and DNS

Part 3 of 10 · H446 1.3.3 · Networks

A request that starts with a typed domain name and ends with a usable page passes through several distinct mechanisms, and H446 1.3.3 expects DNS, IP addressing and packet transfer to be kept apart. This worksheet walks the whole journey in order, then deliberately breaks it with packets that take different routes and arrive out of sequence.

Students will:

  • describe how a domain name is resolved to an IP address
  • explain how data is divided into packets and what the control information supports
  • account for packets travelling by different routes and arriving out of order
  • trace one complete request and response from typed address to application data
  • explain why a receiver must reconstruct in the intended order rather than the order of arrival

Inside: 5 explanation cells, 1 multiple-choice question, 2 fill-in-the-blanks cells and 2 written answers. 23 marks, about 45 to 55 minutes.

Series: H446 1.3.3 · Networks, part 3 of 10.

Shared by Coding PathwayVerified teacher

  • 10 cells
  • About 45 minutes
  • CC BY-SA 4.0
  • Shared 31 Aug 2026
  • Updated 3 Sept 2026

Preview

The whole resource, exactly as a class sees it. Answers and marking are held back.

Internet transfer: packets, IP addresses and DNS

The internet is a global system of interconnected networks. The World Wide Web is one service using it. DNS, IP addressing and packet transfer solve different parts of a request journey.

From a remembered name to a reachable service

Domain name to IP address request and responseBrowser on clientrequests learn.examplethen uses returned IPDNS servicemaps domain nameto 198.51.100.42Destination serveraddress 198.51.100.42returns requested data1 name2 IP3 addressed request packets4 response packets; receiving layers reconstruct usable dataDNS finds an IP address; it does not fetch the page or replace packet transfer.

A URL identifies a resource; its domain name is the human-readable part used for the host. DNS maps that name to an IP address. The client then addresses a request to the destination. DNS does not fetch the resource itself.

Packet transfer at OCR depth

Data is divided into packets. Packet control information supports addressing, numbering/order and reconstruction. Routers forward packets between networks using destination IP information. Packets can take different routes and may arrive out of order; the receiving process reassembles them into usable data.

This route deliberately stops before subnetting, NAT, ports/sockets, ARP and detailed resolver hierarchy because current H446 1.3.3 does not require them.

Fill in the blanks4 marks
The browser supplies a domain name to gap 1, which returns an gap 2. The request is divided into gap 3 and routed between networks. At the destination, the data is gap 4 for the application.
  • DNS
  • IP address
  • packets
  • reassembled
  • URL
Multiple choice1 mark

Which is the most accurate account of DNS?

  • AIt stores every web page and sends its HTML directly
  • BIt guarantees that every packet follows one route
  • CIt maps the domain name from a URL to an IP address used to locate the destination
  • DIt replaces the four TCP/IP layers
Written answer8 marks

Explain the complete high-level journey when a learner enters revision.example/topic and the destination is 198.51.100.42. Include DNS, addressing, packets, possible routes, receipt and application data.

Write an ordered cause-and-effect sequence. Account for both the request and usable response.

Students type their answer here.

Apply the model independently

The remaining tasks change the context or reduce the support. Complete them without copying the worked model, then check that each explanation connects a mechanism to its consequence.

Written answer6 marks

A 3600-byte message is represented as packets P1, P2 and P3. P2 arrives first, P1 arrives by a different route and P3 is delayed. Explain why the receiver should not display P2 + P1 + P3, what information/process is needed, and how route diversity can help if one link fails.

Use sequence information, completeness and reconstruction; do not claim DNS reorders packets.

Students type their answer here.

Fill in the blanks4 marks
The internet links many checkpoint gap 1. DNS maps a domain name to an checkpoint gap 2. Routers use destination addressing to forward checkpoint gap 3. The receiver uses ordering information to checkpoint gap 4 the data.

Review your understanding

Before submitting, check that you can explain the main distinction in your own words, apply it in an unfamiliar context and justify each consequence rather than only naming a feature.