2. Introduction Widespread unstructured P2P network
A Gnutella client has 4-10 TCP connections to other peers
For signalling traffic UDP is used and to make use of the benefits of server based networks a ”ultra-peer” state was created
”Ultra-peer” status is self assigned by powerful peers and provides some extra functionality compared to ordinary nodes
There exist many freely available Gnutella clients
Some of the most popular are:
Limewire
Bearshare
Morpheus
Shareaza
It has the most increasing number of users
It has a very pleasant GUI and connects also to eDonkey and BitTorrent

3. Main Features
This protocol underlies much of the current file-sharing activity on the Internet.
It is based on TCP/IP and HTTP
A file sharing network (fsn) is a bunch of machines that exchange files using gnutella.
To connect to a gnutella network, you need the IP address of one single machine that is already part of the network.

4. Gnutella Peer-to-peer indexing and searching service.
Peer-to-peer point-to-point file downloading using HTTP.
A gnutella node needs a server (or a set of servers) to “start-up”… gnutellahosts.com provides a service with reliable initial connection points
But introduces a new single point of failure!

5. Gnutella vs. Napster
Like Napster, distributed file storage and transmission
Added the ability to distribute file discovery
Ask your direct peers who else they know
Query those machines directly

6. Characteristics Gnutella is a distributed system for file sharing
provide means for network discovery
provide means for file searching and sharing
Defines a network at the application level
Employs the concept of peer-to-peer
all hosts are equal (symmetry)
there is no central point
anonymous search, but reveal the IP addresses when downloading

7. Advantages and Disadvantages
Resource Discovery
Advantages and Disadvantages
Advantages:
Inherent scalability
Avoidance of “single point of litigation” problem
Fault Tolerance
Disadvantages:
Slow information discovery
More query traffic on the network

8. Gnutella in Details Share any type of files (not just music)
Decentralized search unlike Napster
You ask your neighbors for files of interest
Neighbors ask their neighbors, and so on
TTL field quenches messages after a number of hops
Users with matching files reply to you
Figure from

9. Joining Gnutella Network
The new node connects to a well known ‘Anchor’ 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

10. Query flooding Gnutella no hierarchy
use bootstrap node to learn about others
join message
Send query to neighbors
Neighbors forward query to all attached neighbors (floods)
If queried peer has object, it sends message back to querying peer
query
join

11. About the Flooding - DoS
There is nothing that stops a servant flooding its network region with messages.
Cost of maintaining Network
Cost of searching file

12. The Cooperation Spectrum

13. Free Riding File sharing networks rely on users sharing data
Two types of free riding
Downloading but not sharing any data
Not sharing any interesting data
On Gnutella
15% of users contribute 94% of content
63% of users never responded to a query
Didn’t have “interesting” data
Data from E. Adar and B.A. Huberman (2000), “Free Riding on Gnutella”

14. Number of Shared Files

15. Summary store selected files
peer-to-peer networking: applications connect to peer applications
focus: decentralized method of searching for files
each application instance serves to:
store selected files
route queries (file searches) from and to its neighboring peers
respond to queries (serve file) if file stored locally
Gnutella history:
3/14/00: release by AOL, almost immediately withdrawn
too late: 23K users on Gnutella at 8 am this AM
many iterations to fix poor initial design (poor design turned many people off)
What we care about:
How much traffic does one query generate?
how many hosts can it support at once?
What is the latency associated with querying?
Is there a bottleneck?

16. Screenshots – Gnutella
Logging ….

17. Screenshots – Gnutella Searching & Downloading ….

18. Image of the Gnutella network

19. Image of the Gnutella network

20. Image of the Gnutella network