Gnutella, Freenet and Peer to Peer Networks

Gnutella, Freenet and

Peer to Peer Networks



By

Norman Eng

Steven Hnatko

George Papadopoulos

Peer to Peer

Fundamentals

No dedicated servers or hierarchy among the

computers

All of the computers are equal

Each computer functions as a client and a server with

no administrator

User on each computer decides what data on their

computer will be shared on the network.

Gnutella and Freenet

Freenet and Gnutella are two leading

protocols for Peer to Peer networking

 They both create a decentralized network

of computers, but do so with different

implementations

 They handle and distribute data differently

according to their own project goals

Freenet and Gnutella

Freenet and Gnutella are two leading protocols for

peer to peer networking

 Both create a decentralized network of computers, but do so

with different implementations

 They handle and distribute data differently according to their

own project goals

 Gnutella has a much broader user base than Freenet at this

time, due to its easier implementation

Gnutella Basics

Gnutella works by “viral propagation”

 Each node of the network simultaneously acts

as a client and server, conducting searches

while listening for incoming queries

 Gnutella defines these heterogeneous nodes as

“servents”

Gnutella Basics (cont.)

Properties of the Gnutella Network:

 Every node is equal

 Every node is both a server as well as a

client

Problems with the Gnutella Network:

 The Network cannot be described as a

tree, because there is no hierarchy

 The Network can be cyclical, this causes

excessive traffic

Standard Interactions

Connecting to a Server(node)

 A node connecting to the network must first connect to a

know node

 Client Says: GNUTELLA CONNECT

 Server Responds: GNUTELLA OK

Downloading from a Server(node)

 HTTP Downloading

 Client Request String:

 GET /get/1234/bob.mp3 HTTP/1.0

 Connection: Keep-Alive

 Server Response:

 HTTP 200 OK

 Server:Gnutella

 Content-type:application/binary

 Content-length:3289

Gnutella Descriptor

Information

Ping

 Used to actively discover hosts on the network

Pong

 The response to a Ping

Query

 The primary mechanism for searching the distributed

network

Query Hit

 The response to a Query

Push/Get

 A mechanism that allows a “servent” to contribute/receive

file-based data to the network

HTTP Message Format





3 Major Fields of Information:

 Initial line signaling Request/Response

 Headers (not mandatory)



 Additional Data (not mandatory)

Protocol

 To discover nodes, a servent will send out a Ping

descriptor

 A servent receiving a Ping is expected to respond

with a Pong and forward the Ping to all other

nodes it is connected to, decreasing the TTL

before forwarding

 Pongs may only be sent along the same path as

the incoming Ping

 A search is propagated using a Query descriptor

which is also routed to nodes and other nodes

connected to them

Protocol Diagram



3) Routed Ping 2) Outgoing Pong

node



1) Incoming Ping









Discovery

Protocol Diagram







1) Query 2) QueryHit



1) File Transfer







Search Transfer

How Gnutella Retrieves

Information

Freenet Overview

Objectives of Freenet Protocol

 Anonymity for both producers and

consumers of information

 Deniability for storers of information

 Resistance to attempts by third parties to

deny access to information

 Efficient dynamic storage and routing of

information

 Decentralization of all network function

Freenet Basics

Network of equal nodes, each acting as

client and server

Information stored on hosts under

searchable keys

Total anonymity of users

 Owner of node has no knowledge of information in

node’s datastore

 Data stored within nodes is encrypted

Freenet Interactions

Connection to Freenet network

 Node connecting to network must obtain existing

node’s address though out-of-band means

 Once connected, a new node message is

propagated to randomly selected, connected

nodes so existing nodes learn of new node’s

existence

Freenet Interactions

File Searches

 Node’s search string is hashed to key and own datastore

checked on key

 If failure, key is sent to one connected node which searches

it’s datastore and if fails, propagates search to one of it’s

connected nodes, HTL decreased

 When file is found, search terminates and data is sent back

to searching node, each node along path to searching node

copies data to its own datastore as well

Freenet Searches

Freenet Details

Datastore Key Types

 Keyword Signed Key (KSK)

 Content Hash Key (CHK) Most Common

 Name defined by data itself

 Signature Verified Key (SVK)

 Provide a “private” key for use with SSK

 SubSpace Key (SSK)

 Allow users to insert data “under” an SVK

 Can create hierarchical data structure under SVK

Freenet Details

Common Message Header Information

 UniqueID: 64bit value assigned to generated

message, used to prevent loops

 HopsToLive: Number of times a message may be

forwarded before destroyed

 Depth: Distance in hops a message has traveled

from its creator

 Source: Address identifying sender of message

Freenet Details

Message Types

 HandshakeRequest

 Initiate connection to a node, ensures that node

is connected and protocol versions match

 HandshakeReply

 Response to HandshakeRequest

 DataRequest

 Request from node for data transmission, must

provide key for data as well

Freenet Details

Message Types (cont)

 DataReply

 Reply of requested data, must provide data to be stored

 DataInsert

 Request from a node for data to be stored onto network,

requesting node includes data and key

 RequestFailed

 Signals to sending node that data request failed

Major Differences

Manner in which data is stored



Level of Anonymity



Developer’s Project Design Goals