Networks and the Internet: Question 7

Worked solution

Part (a): Identifying the model

This scenario uses the peer-to-peer model. In a peer-to-peer network, every device is an equal “peer” that can act as both a provider and a requester of resources, and no single device is designated as a central server.

The feature of the scenario that supports this is that any laptop can send a file directly to, or receive a file directly from, any other laptop, and there is no dedicated central computer storing the master copy. Exactly the opposite of the client-server model, where one fixed server would centrally store the files and the other computers would only request them as clients.

[2 marks]: [1] for correctly stating “peer-to-peer”, [1] for a valid supporting feature from the scenario (every laptop can act as both sender and receiver, with no central server).

Part (b): Advantage and disadvantage of peer-to-peer here

Advantage. Because there is no dedicated server, the collective avoids the cost and effort of buying, configuring and maintaining a separate server machine, for only three designers, this keeps the arrangement cheap and simple. It also means there is no single central computer whose failure would stop every file exchange; if one laptop is switched off, the other two can still share files with each other.

Disadvantage. Since every laptop can hold, and independently edit, its own copy of a design file, there is no single authoritative version that everyone automatically works from. Different laptops can easily end up holding different, conflicting versions of what should be the same file, because peer-to-peer has no central copy to keep everyone synchronised against.

[4 marks]: [2] for a correctly explained advantage tied to this scenario (lower cost/no dedicated server, or no single point of failure for file exchange), [2] for a correctly explained disadvantage tied to this scenario (risk of conflicting/out-of-sync copies without a central master file).

Part (c): Would client-server help?

Yes. Introducing a dedicated server would give the collective exactly what it now wants. The server would hold the single, authoritative copy of each design file, and every designer’s computer would become a client, requesting the current version and submitting updates to that one copy. This removes the risk of different laptops silently drifting apart into conflicting versions, which was the disadvantage identified in part (b).

A central server also gives the administrator one place to set and enforce access permissions (for example, who may open or edit a particular file), something that is far harder to guarantee consistently across three independent laptops sharing files directly with each other in a peer-to-peer arrangement.

[3 marks]: [1] for stating “yes”, [1] for explaining the benefit for a single authoritative/up-to-date copy, [1] for explaining the benefit for centrally controlled access permissions.

Final answers

• (a) Peer-to-peer model. Every laptop can send to and receive from any other laptop directly, with no dedicated central server.
• (b) Advantage: cheaper and simpler, with no single point of failure for file exchange. Disadvantage: laptops can end up with conflicting versions of the same file with no central master copy.
• (c) Yes. A dedicated server would hold one authoritative copy of each file and let one administrator centrally control access permissions.