David introduces himself and provides links to his website, blog, and GitHub profile. He discusses his work on resource discovery for decentralized web applications using a peer-to-peer overlay network with WebRTC for transport. Specifically, he created a proof-of-concept called webrtc-explorer that implements a Chord-inspired distributed hash table on top of WebRTC to enable peer-to-peer messaging between browsers. The document provides details on how Chord works and an example of using the webrtc-explorer library.

1. HI, I’M DAVID
://daviddias.me
://blog.daviddias.me
://github.com/diasdavid
://twitter.com/daviddias

3. RESOURCE DISCOVERY

4. RESOURCE DISCOVERY FOR THE
WEB PLATFORM ON TOP OF A P2P
OVERLAY NETWORK USING WEBRTC
AS THE LAYER OF TRANSPORT

5. THE INTERNET

7. MEMEX

8. URL

9. {
“KEY” : ”VALUE”
}

10. GET http://recipes.com/francesinha

11. GET http://recipes.com/latest

12. GET http://recipes.com/latest

13. GET http://recipes.com/latest

14. GET http://recipes.com/latest LB

15. GET http://recipes.com/latest LB
Centralized

16. GET http://recipes.com/latest
L
L L
L

18. DECENTRALISED
ARCHITECTURES

20. P2P networks are only as useful as their Resource
Discovery capabilities remain efficient when they scale up

21. GNUTELA 0.4

23. • march 2000, Justin Frankel and Tom Pepper
• topology is completely random
• routing and search using flooding with TTL
and hop counter
• really slow
• lot’s of signalling traffic

29. GNUTELA 0.6

31. UNSTRUCTURED
P2P NETWORKS
Without an implicit way to organize content

32. STRUCTURED
P2P NETWORKS

33. CHORD

34. • DHT
• Highly scalable
• Each node only knows of m number of other nodes
• Each node has a unique identifier
• Each node is responsible for a segment of the data
• Ids are 160 bits (SHA-1 for Uniform Distribution)
• CHORD is awesome

36. 02160
• 160 bit
namespace

37. 0
1
2
3
4
5
6
7
• 3 bit
namespace
• Id = hash(IP)

38. 0
1
2
3
4
5
6
7
• each node is
responsible for
a segment

39. 0
1
2
3
4
5
6
7
• minimum
requirement -
each node has
to know their
successor

40. 0
1
2
3
4
5
6
7
• each node is
going to have
it’s finger table

41. start interval sucessor
start(k) = (n+2k-1) mod 2m, 1 ≤ k ≤ m
interval(k) = start(k) = start(k+1)
sucessor - first node after start(k)

42. 0
1
2
3
4
5
6
7
start interval sucessor
start(k) = (n+2k-1) mod 2m, 1 ≤ k ≤ m
interval(k) = [start(k), start(k+1) )
sucessor - first node after start(k)

43. 0
1
2
3
4
5
6
7
start interval sucessor
1
start(k) = (n+2k-1) mod 2m, 1 ≤ k ≤ m
interval(k) = [start(k), start(k+1) )
sucessor - first node after start(k)
interval(k) =
[(0+2*1-1) mod 23 ,
(0+2*2-1) mod 23) =
[1,2)

44. 0
1
2
3
4
5
6
7
start interval sucessor
1 [1,2) 1
start(k) = (n+2k-1) mod 2m, 1 ≤ k ≤ m
interval(k) = [start(k), start(k+1) )
sucessor - first node after start(k)
interval(k) =
[(0+2*1-1) mod 23 ,
(0+2*2-1) mod 23) =

45. 0
1
2
3
4
5
6
7
start interval sucessor
1 [1,2) 1
2
start(k) = (n+2k-1) mod 2m, 1 ≤ k ≤ m
interval(k) = [start(k), start(k+1) )
sucessor - first node after start(k)
interval(k) =
[(0+2*2-1) mod 23 ,
(0+2*3-1) mod 23)

46. 0
1
2
3
4
5
6
7
start interval sucessor
1 [1,2) 1
2 [2,4) 3
start(k) = (n+2k-1) mod 2m, 1 ≤ k ≤ m
interval(k) = [start(k), start(k+1) )
sucessor - first node after start(k)
interval(k) =
[(0+2*2-1) mod 23 ,
(0+2*3-1) mod 23)

47. 0
1
2
3
4
5
6
7
start interval sucessor
1 [1,2) 1
2 [2,4) 3
4
start(k) = (n+2k-1) mod 2m, 1 ≤ k ≤ m
interval(k) = [start(k), start(k+1) )
sucessor - first node after start(k)
interval(k) =
[(0+2*3-1) mod 23 ,
(0+2*4-1) mod 23)

48. 0
1
2
3
4
5
6
7
start interval sucessor
1 [1,2) 1
2 [2,4) 3
4 [4,0) 6
start(k) = (n+2k-1) mod 2m, 1 ≤ k ≤ m
interval(k) = [start(k), start(k+1) )
sucessor - first node after start(k)
interval(k) =
[(0+2*3-1) mod 23 ,
(0+2*4-1) mod 23)

50. • API drafted by W3C
• enables voice, video and data transfer between
browsers in a P2P fashion

62. DEMO

63. WEBRTC-EXPLORER

64. • Chord inspired P2P overlay network
designed for the Web Platform
• Uses CHORD routing scheme
• Uses WebRTC for transport
• WebSockets for Signalling
• Peers (browsers) route messages amongst
them
• 48 bits Ids
• Brings a full DHT to the browser
WEBRTC-EXPLORER

65. WEBRTC-RING
http://blog.daviddias.me/
2014/12/20/webrtc-ring

66. HOW DOES IT WORK

67. var Explorer = require(‘webrtc-explorer’);
var config = {
signalingURL: '<url>'
};
var peer = new Explorer(config);
peer.events.on(‘registered', function(data) {
console.log('Id:', data.peerId);
});
peer.events.on('ready', function() {
console.log('ready to send messages');
});
peer.events.on('message', function(envelope) {
console.log(envelope);
});
peer.register();
//peer.send(‘<dst_id>’, <data_to_send>);
s-register
c-registered
{
id: “<this_node_id>”
}
1
2

68. c-finger-update
c-finger-update
c-finger-update

69. s-send-offer
c-offer-accepted
1
4
s-accept-offer
s-offer-accepted
2
3
5

70. DEMO

71. PAPERS
• A study on peer-to-peer based discovery of grid resource information by
Rajiv Ranjan, Aaron Harwood, Rajkumar Buyya
• Peer-to-peer architecture case study: Gnutella network by M. Ripeanu
• Dynamo : Amazon ’ s Highly Available Key-value Store by Giuseppe
DeCandia, Deniz Hastorun, Madan Jampani, Gunavardhan Kakulapati, Avinash
Lakshman, Alex Pilchin, Swaminathan Sivasubramanian, Peter Vosshall, Werner
Vogels
• The Gnutella Protocol Specification v0.6 by Tor Klingberg, Raphael Manfredi
• Chord : A Scalable Peer-to-peer Lookup Service for Internet by Ion Stoica,
Robert Morris, David Karger, M Frans Kaashoek, Hari Balakrishnan Ý

72. THANK YOU! :D