Peer-to-Peer

Question 1

Distinguish between centralised and decentralised P2P networks

Answer 1

In a centralised network, the directory system uses the client-server paradigm, but storing
and downloading of the files are done using peer-to-peer paradigm.
A decentralised network does not depend on a central directory system

Question 2

What are the advantages and disadvantages of a centralised P2P network?

Answer 2

A central network makes the maintenance of the directory simple, but has such drawbacks
such as creating huge traffic and vulnerability to attacks.

Question 3

What are the advantages and disadvantages of a decentralised P2P network?

Answer 3

A decentralised network generates less traffic and is less vulnerable to attacks, but is more
difficult to build.

Question 4

Distinguish between structured and unstructured decentralised P2P networks.

Answer 4

In an unstructured network, the nodes are linked together randomly. A structured network
uses a predefined set of rules to link nodes together.

Question 5

How many points in a DHT with m = 10?

Answer 5

The number of points is 210 or 1024

Question 6

Explain problems encountered if IP addresses are used as the node identifiers in a DHT

Answer 6

There are not only IP addresses that we need to store; we need to store other identities such
as filenames. A hash function creates a unified set of id object entities

Question 7

Explain two strategies used for storing an object in a DHT-based network.

Answer 7

The two strategies are called direct and indirect.
1) In the direct strategy, the object is stored in a peer whose ID is somehow closest to the
object ID.
2) In the indirect strategy, the object is stored in a peer that owns the object, but a reference
is stored in a peer whose ID is somehow closest to the object ID.