1. P2P Networking 2010

2. Client/Server Architecture
GET /index.html HTTP/1.0
HTTP/ OK ...
Server
Clients

3. Peer-to-Peer Architecture
Gateway Server
Peers

4. The architectures Server-based architecture
Client-Server / Server-Cluster
Problems：
Limited resources
All loads are centered on the server
Server-based architecture has low scalability.
The setup and maintenance cost is high.
Peer-to-Peer (P2P) architecture
Advantages：
Distributing loads to all users
Users consume and provide resources
P2P architecture has high scalability.
The setup and maintenance cost is low.

5. The Client Side
Today’s clients can perform more roles than just forwarding users requests
Today’s clients have:
more computing power
more storage space
Thin client  Fat client

6. Evolution at the Client Side
IBM 8-bit PC
@ 4.77MHz
360k diskettes
64-bit 4-core 4GHz 750GB HD
DEC’S VT100
No storage
2010
‘70
‘80

7. What Else Has Changed? Peer-to-Peer (P2P)
The number of home PCs is increasing rapidly
Most of the PCs are “fat clients”
As the Internet usage grow, more and more PCs are connecting to the global net
Most of the time PCs are idle
How can we use all this?
Peer-to-Peer (P2P)

8. What is peer-to-peer (P2P)?
“Peer-to-peer is a way of structuring distributed applications such that the individual nodes have symmetric roles. Rather than being divided into clients and servers each with quite distinct roles, in P2P applications a node may act as both a client and a server.” -- Charter of Peer-to-peer Research Group, IETF/IRTF, June 24, 2004 (

9. Resources Sharing What can we share?
Computer-related resources
Shareable related-computer resources:
CPU cycles GIMPS
Bandwidth - PPLive, PPStream
Storage Space OceanStore, Murex
Data Napster, Gnutella
People - Buddy Finder
Camera, Microphone, Sensor, Service???

10. SETI@Home SETI – Search for Extra-Terrestrial Intelligence
@Home – On your own computer
A radio telescope in Puerto Rico scans the sky for radio signals
Fills a DAT tape of 35GB in 15 hours
That data have to be analyzed

11. - Example

18. MUREX: A Mutable Replica Control Scheme for Peer-to-Peer Storage Systems
Jehn-Ruey Jiang
ACN Lab NCU

19. Murex: Basic Concept
HotOS
Attendee

20. Peer-to-Peer Video Streaming…
Video stream

23. Napster -- Shawn Fanning

27. Napster Sharing Style: hybrid center+edge
Title User Speed
song1.mp beasiteboy DSL
song2.mp beasiteboy DSL
song3.mp beasiteboy DSL
song4.mp kingrook T1
song5.mp kingrook T1
song5.mp slashdot
song6.mp kingrook T1
song6.mp slashdot
song7.mp slashdot
1. Users launch Napster and connect to Napster server
2. Napster creates dynamic directory from users’ personal .mp3 libraries
3. beastieboy enters search criteria s o n g 5
“beastieboy”
song1.mp3
song2.mp3
song3.mp3
“kingrook”
song4.mp3
song5.mp3
song6.mp3
“slashdot”
song5.mp3
song6.mp3
song7.mp3
4. Napster displays matches to beastieboy
5. beastieboy makes direct connection to kingrook for file transfer
song5.mp3

28. History of Napster
5/99: Shawn Fanning (freshman, Northeastern University) founds Napster Online (supported by Groove)
12/99: First lawsuit
7/01: simultaneous online users 160K
6/02: file bankrupt …
10/03: Napster 2 (Supported by Roxio) (users should pay $9.99/month)

29. Gnutella -- Justin Frankel and Tom Pepper
Gnutella (pronounced: /nʊˈtɛlə/ with a silent g, or alternatively /gnʊˈtɛlə/, following R. M. Stallman’s pronunciation of GNU) is a file sharing network. As of December 2005, Gnutella is the third-most-popular file sharing network on the Internet, following eDonkey 2000 and FastTrack. Gnutella is thought to host on an average of approximately 2.2 million users, although around 750,000-1,000,000 are on-line at any given moment.[1]

30. GNU: Recursive Acronym
The ‘Animal’ GNU
GNU: Recursive Acronym
GNU’s Not Unix …. +
Gnutella =
GNU
Nutella
Nutella: a hazelnut chocolate spread produced by the Italian confectioner Ferrero ….

31. GNU
GNU's Not Unix
1983 Richard Stallman (MIT) established Free Software Foundation and Proposed GNU Project
Free software is not freeware
GPL: GNU General Public License

32. Gnutella History
Gnutella was written by Justin Frankel, the 21-year-old founder of Nullsoft.
(Nullsoft acquired by AOL, June 1999)
Nullsoft (maker of WinAmp) posted Gnutella on the Web, March 14, 2000.
A day later AOL yanked Gnutella, at the behest of Time Warner.
Too late: 23k users on Gnutella
People had already downloaded and shared the program.
Gnutella continues today, run by independent programmers.

33. Scenario: Joining Gnutella Network
Gnutella Protocol
Scenario: Joining Gnutella Network
Gnutella Network
The new node connects to a well known ‘Anchor’ node or ‘Bootstrap’ node.
Then sends a PING message to discover other nodes.
PONG messages are sent in reply from hosts offering new connections with the new node.
Direct connections are then made to the newly discovered nodes.
New
PING
PING
PING
PONG
PING
PING A
PING
PING
PONG
PING
PING
PING

34. Peer-to-Peer Overlay Network
Focus at the application layer

35. Peer-to-Peer Overlay Network
End systems
one hop
(end-to-end comm.)
a TCP thru the Internet
Internet

36. Topology of a Gnutella Network

37. Gnutella: Issue a Request
xyz.mp3 ?

38. Gnutella: Flood the Request

39. Gnutella: Reply with the File
Fully distributed storage and directory!
xyz.mp3

40. n: number of participating nodes
So Far
n: number of participating nodes
Centralized :
- Directory size – O(n)
- Number of hops – O(1)
Flooded queries:
- Directory size – O(1)
- Number of hops – O(n)

41. We Want Efficiency : O(log(n)) messages per lookup
Scalability : O(log(n)) state per node
Robustness : surviving massive failures

42. How Can It Be Done? How do you search in O(log(n)) time? Binary search
You need an ordered array
How can you order nodes in a network and data objects?
Hash function!

43. Object ID (key):AABBCC
Example of Hasing
SHA-1
Object ID (key):AABBCC
Shark
SHA-1
Object ID (key):DE11AC
:8080

44. Basic Idea Place object to the peer with closest hash keys P2P Network
Publish (H(y))
Join (H(x))
Object “y”
Peer “x”
H(y)
H(x)
Objects have hash keys
Peer nodes also have hash keys in the same hash space y x
Hash key
Place object to the peer with closest hash keys

45. Mapping an object to the closest node with a larger keyM
- a node
- an data object

46. Viewed as a Distributed Hash Table
2128-1
Hash
table
Peer
node
Internet

47. DHT Distributed Hash Table
Input: key (file name) Output: value (file location)
Each node is responsible for a range of the hash table, according to the node’s hash key. Objects’ directories are placed in (managed by) the node with the closest key
It must be adaptive to dynamic node joining and leaving

48. How to Find an Object?
2128-1
Hash
table
Peer
node

49. Simple Idea
Track peers which allow us to move quickly across the hash space
a peer p tracks those peers responsible for hash keys (p+2i-1), i=1,..,m i
i+22
i+24
i+28
2128-1
Hash
table
Peer
node

50. Chord Lookup – with finger table
Start
Int.
node
2+1
[3,4) 3
2+2
[4,6) 7
2+4
[6,10)
2+8
[10,2) 10
O(log n) hops (messages) for each lookup!! 1
I’m node 2.
Please find key 14! 15 14 2
14 ∈[10,2)
O(log n) states per node 3 12
Start
Int.
node
10+1
[11,12) 12
10+2
[12,14)
10+4
[14,2) 14
10+8
[2,10) 2
Circular 4-bit
ID space 10
14 ∈[14,2) 7

51. Classification of P2P systems
Hybrid P2P – Preserves some of the traditional C/S architecture. A central server links between clients, stores indices tables, etc
Napster
Unstructured P2P – no control over topology and file placement
Gnutella, Morpheus, Kazaa, etc
Structured P2P – topology is tightly controlled and placement of files are not random
Chord, CAN, Pastry, Tornado, etc
Morpheus
the Greek god of dreams and of sl51p
【希】【神話】睡夢之神
Tornado
a violent and destructive whirlwind, in the form of a funnel-shaped cloud moving on a long and narrow path
龍捲風

52. Q&A