P2P Content Distribution Bittorrent and Spotify

P2P Content Distribution BitTorrent and Spotify

Amirkabir University of Technology (Tehran Polytechnic)

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 1 / 62 Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 2 / 62 Possible Solutions for Content Distribution

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 3 / 62 Client-Server Model

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 4 / 62 Client-Server Model

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 5 / 62 Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 6 / 62 I Single Point of failure?

The Client-Server Model Problems

I Scalability?

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 7 / 62 The Client-Server Model Problems

I Scalability?

I Single Point of failure?

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 7 / 62 The Client-Server Model Problems

I Scalability?

I Single Point of failure?

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 7 / 62 Client-Server Systems

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 8 / 62 The Client-Server Model Problem

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 9 / 62 Scalable and Fault-Tolerant Client-Server Model

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 10 / 62 Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 11 / 62 Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 12 / 62 Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 13 / 62 Peer-to-Peer Model

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 14 / 62 Peer-to-Peer (P2P) Model

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 15 / 62 P2P Challenges

I Churn in the system

I Free-riding problem

I Bottleneck in the overlay network

I Connectivity problem, e.g., NAT

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 16 / 62 Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 17 / 62 Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 18 / 62 How To Discover Data?

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 19 / 62 Possible Solutions - First Generation

I Central directory

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 20 / 62 Possible Solutions - Second Generation

I Flooding

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 21 / 62 Possible Solutions - Third Generation

I Distributed Hash Table (DHT)

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 22 / 62 P2P Content Distribution Applications - File Sharing

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 23 / 62 P2P Content Distribution Applications - Media Streaming

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 24 / 62 Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 25 / 62 BitTorrent

I BitTorrent is a system for eﬃcient and scalable replication of large amounts of static data.

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 26 / 62 BitTorrent Players

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 27 / 62 Files

I Files are broken into pieces of size between 64KB and 1MB.

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 28 / 62 .torrent Files

I Metadata

I Contains: • URL of tracker • Information about the ﬁle, e.g., ﬁlename, length, ...

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 29 / 62 I It, then, connects to the tracker.

I The tracker tells the peers from which other peers to download the pieces of the ﬁle.

I Peers use this information to communicate with each other.

I The peers send information about the ﬁle and themselves to tracker.

The Core Idea

I A peer obtains .torrent ﬁle.

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 30 / 62 I The tracker tells the peers from which other peers to download the pieces of the ﬁle.

I Peers use this information to communicate with each other.

I The peers send information about the ﬁle and themselves to tracker.

The Core Idea

I A peer obtains .torrent ﬁle.

I It, then, connects to the tracker.

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 30 / 62 I Peers use this information to communicate with each other.

I The peers send information about the ﬁle and themselves to tracker.

The Core Idea

I A peer obtains .torrent ﬁle.

I It, then, connects to the tracker.

I The tracker tells the peers from which other peers to download the pieces of the ﬁle.

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 30 / 62 I The peers send information about the ﬁle and themselves to tracker.

The Core Idea

I A peer obtains .torrent ﬁle.

I It, then, connects to the tracker.

I The tracker tells the peers from which other peers to download the pieces of the ﬁle.

I Peers use this information to communicate with each other.

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 30 / 62 The Core Idea

I A peer obtains .torrent ﬁle.

I It, then, connects to the tracker.

I The tracker tells the peers from which other peers to download the pieces of the ﬁle.

I Peers use this information to communicate with each other.

I The peers send information about the ﬁle and themselves to tracker.

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 30 / 62 Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 31 / 62 Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 32 / 62 Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 33 / 62 Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 34 / 62 Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 35 / 62 Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 36 / 62 Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 37 / 62 Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 38 / 62 Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 39 / 62 Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 40 / 62 What About Free Riders?

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 41 / 62 Tit-For-Tat

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 42 / 62 Question

I From which peers download the pieces?

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 43 / 62 Peer Selection

I Use choking algorithm to choose peer to download pieces.

I Decision to choke/unchoke based on tit-for-tat.

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 44 / 62 Discover More Cooperating Peers

I Optimistic unchoking

I Allocate an upload slot to a randomly chosen uncooperative peer

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 45 / 62 Snubbed Peers

I If all its peers choke it.

I Increase the number of optimistic unchokes.

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 46 / 62 Question

I Which piece?

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 47 / 62 I Random ﬁrst piece: start-up need to get a complete piece

I Endgame mode: broadcast for all remaining blocks

Piece Selection

I Rarest ﬁrst: common parts left for later

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 48 / 62 I Endgame mode: broadcast for all remaining blocks

Piece Selection

I Rarest ﬁrst: common parts left for later

I Random ﬁrst piece: start-up need to get a complete piece

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 48 / 62 Piece Selection

I Rarest ﬁrst: common parts left for later

I Random ﬁrst piece: start-up need to get a complete piece

I Endgame mode: broadcast for all remaining blocks

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 48 / 62 BitTorrent Extension

I Distributed tracker

I Peer-exchange

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 49 / 62 Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 50 / 62 Spotify

I Active users: over 50 million

I Number of songs: over 20 million

I Number of songs added per day: over 20000

I Number of playlists: over 1.5 billion created so far

I Available in 58 countries

I Legal

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 51 / 62 I Meanwhile, search P2P network for remainder.

I Switch back and forth between Spotify servers and peers as needed.

I Towards end of a track, start prefetching the next one.

The Core Idea

I Request ﬁrst piece from Spotify servers.

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 52 / 62 I Switch back and forth between Spotify servers and peers as needed.

I Towards end of a track, start prefetching the next one.

The Core Idea

I Request ﬁrst piece from Spotify servers.

I Meanwhile, search P2P network for remainder.

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 52 / 62 I Towards end of a track, start prefetching the next one.

The Core Idea

I Request ﬁrst piece from Spotify servers.

I Meanwhile, search P2P network for remainder.

I Switch back and forth between Spotify servers and peers as needed.

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 52 / 62 The Core Idea

I Request ﬁrst piece from Spotify servers.

I Meanwhile, search P2P network for remainder.

I Switch back and forth between Spotify servers and peers as needed.

I Towards end of a track, start prefetching the next one.

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 52 / 62 Main Problem in Using Spotify P2P Network

Peer Discovery

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 53 / 62 I Broadcast query in small (2 hops) neighborhood in overlay (Gnutella style)

I LAN peer discovery

Peer Discovery

I Sever-side tracker(BitTorrent style) • Only remembers 20 peers per track. • Returns 10 (online) peers to client on query.

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 54 / 62 I LAN peer discovery

Peer Discovery

I Sever-side tracker(BitTorrent style) • Only remembers 20 peers per track. • Returns 10 (online) peers to client on query.

I Broadcast query in small (2 hops) neighborhood in overlay (Gnutella style)

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 54 / 62 Peer Discovery

I Sever-side tracker(BitTorrent style) • Only remembers 20 peers per track. • Returns 10 (online) peers to client on query.

I Broadcast query in small (2 hops) neighborhood in overlay (Gnutella style)

I LAN peer discovery

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 54 / 62 I If a peer is slow, re-request from new peers.

I When buﬀers are low, download from central server as well.

I If buﬀers are very low, stop uploading.

Downloading in P2P

I Ask for most urgent pieces ﬁrst.

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 55 / 62 I When buﬀers are low, download from central server as well.

I If buﬀers are very low, stop uploading.

Downloading in P2P

I Ask for most urgent pieces ﬁrst.

I If a peer is slow, re-request from new peers.

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 55 / 62 I If buﬀers are very low, stop uploading.

Downloading in P2P

I Ask for most urgent pieces ﬁrst.

I If a peer is slow, re-request from new peers.

I When buﬀers are low, download from central server as well.

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 55 / 62 Downloading in P2P

I Ask for most urgent pieces ﬁrst.

I If a peer is slow, re-request from new peers.

I When buﬀers are low, download from central server as well.

I If buﬀers are very low, stop uploading.

Amir H. Payberah (Tehran Polytechnic) P2P Content Distribution 1393/8/27 55 / 62 I Does not inform peers about downloaded blocks.

I Downloads blocks in order.

I Does not enforce fairness (such as tit-for-tat).

I Informs peers about urgency of request.

Spotify vs. BitTorrent