Peer-to-Peer

Question 1

How do P2P networks deal with scability?

Answer 1

As the number of peers increases, so does the computational power, memory and bandwidth.

Question 2

What are the challenges of P2P networks?

Answer 2

Distribution of data
Failure handling
Access to distributed data

Question 3

What is churn?

Answer 3

Independent arrival and departure of thousands or millions of peers.

Question 4

What lessons were learned from Napster?

Answer 4

Pure P2P infeasible.
Server-based indexing causes bottlenecks.
Specific file feature makes design simpler (music files immutable).

Question 5

How does BitTorrent work?

Answer 5

Files split into chunks, peers can download different chunks of files from different peers in parallel.
The more a peer uploads, the more favourably they are looked upon.
If a peer doesn’t upload enough chunks, it is choked from the network.

Question 6

What is a seeder and leecher?

Answer 6

Seeder: A peer with all the chunks of a file.
Leecher: A peer with some of the chunks of a file.

Question 7

How is BitTorrent decentralised?

Answer 7

Each peer can act as a tracker for a file.
Peers arranged in a ring, stored a Distributed Hash Table.
DHT lets peers find which peers are trackers for files.