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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:
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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
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.
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!
Gnutella vs. Napster
Like Napster, distributed file storage and
transmission
Added the ability to distribute file discovery
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Ask your direct peers who else they know
Query those machines directly
Characteristics
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Gnutella is a distributed system for file
sharing
provide means for network discovery
provide means for file searching and sharing
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Defines a network at the application level
Employs the concept of peer-to-peer
all hosts are equal (symmetry)
there is no central point
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anonymous search, but reveal the IP addresses
when downloading
Resource Discovery
Advantages and Disadvantages
Advantages:
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Inherent scalability
Avoidance of “single point of litigation”
problem
Fault Tolerance
Disadvantages:
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Slow information discovery
More query traffic on the network
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
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TTL field quenches
messages after a
number of hops
Users with matching
files reply to you
Figure from http://computer.howstuffworks.com/file-sharing.htm
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.
Gnutella Network
New
PING
PING
PONG
PING
A
PING
PONG
PING
PING
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
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
The Cooperation Spectrum
Free Riding
File sharing networks rely on users sharing data
Two types of free riding
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Downloading but not sharing any data
Not sharing any interesting data
On Gnutella
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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”
Number of Shared Files
Summary
peer-to-peer networking: applications connect to peer applications
focus: decentralized method of searching for files
each application instance serves to:
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store selected files
route queries (file searches) from and to its neighboring
peers
respond to queries (serve file) if file stored locally
Gnutella history:
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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:
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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?
Screenshots – Gnutella
Logging ….
Screenshots – Gnutella
Searching & Downloading ….
Image of the
Gnutella network
Image of the
Gnutella network
Image of the
Gnutella network