Gnutella, Freenet and Peer to Peer Networks

1
Gnutella, Freenet and Peer to Peer Networks

• By
• Norman Eng
• Steven Hnatko
• George Papadopoulos

2
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.

3
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

4
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

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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

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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

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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
• ServerGnutella
• Content-typeapplication/binary
• Content-length3289

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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

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HTTP Message Format

• 3 Major Fields of Information
• Initial line signaling Request/Response
• Headers (not mandatory)
• Additional Data (not mandatory)

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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

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Protocol Diagram
2) Outgoing Pong
3) Routed Ping
node
1) Incoming Ping
Discovery
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Protocol Diagram
1) Query
2) QueryHit
1) File Transfer
Search
Transfer
13
How Gnutella Retrieves Information
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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

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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
  nodes datastore
• Data stored within nodes is encrypted

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Freenet Interactions

• Connection to Freenet network
• Node connecting to network must obtain existing
  nodes 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 nodes existence

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Freenet Interactions

• File Searches
• Nodes search string is hashed to key and own
  datastore checked on key
• If failure, key is sent to one connected node
  which searches its datastore and if fails,
  propagates search to one of its 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

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Freenet Searches
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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

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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

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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

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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

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Major Differences

• Manner in which data is stored
• Level of Anonymity
• Developers Project Design Goals