An Example Architecture for CS179i based on Gnutella and Python

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An Example Architecture for CS179ibased on
Gnutella and Python

• Yihua He

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Sources

• Gnutella Protocol v0.4
• Norman Matloffs Introduction to Threads
  Programming with Python
• Gnutella Developers Forum (GDF)
• Sources available online at www.cs.ucr.edu/yhe/cs
  179i
• Trying to keep updated

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Basic Components

• A Gnutella Server
• Setup and maintain connection with neighbors
• Routing Pings/Pongs and Querys/QueryHits
• A local searching mechanism
• A Gnutella Client
• Customized FTP/HTTP server and client for
  retrieving target files.

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Data Structures Neighbor Table

• NeighborTable
• Fields IP, TimeStamp
• Keep track of current active neighbors. Neighbors
  are supposed to send pings periodically in order
  to keep themselves active. Timeout neighbors will
  be deleted from NeighborTable.
• RoutingHistory
• FileSharingTable

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Data Structures Neighbor Table

• NeighborTable
• Fields IP, TimeStamp
• Keep track of current active neighbors. Neighbors
  are supposed to send pings periodically in order
  to keep themselves active. Timeout neighbors will
  be deleted from NeighborTable.
• RoutingHistory
• FileSharingTable

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Data Structures RoutingHistory

• NeighborTable
• RoutingHistory
• Fields DescriptionID, MsgType, SourceIP,
  Timestamp
• Pong/QueryHit descriptors may only be sent back
  along the same path that carried the orginal
  Ping/Query descriptors.
• To limit the size of RoutingHistory Table,
  entries will be deleted after a certain period of
  time (timeout Soft state)
• FileSharingTable

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Data StructuresFileSharing Table

• NeighborTable
• RoutingHistory
• FileSharingTable
• Fields FileID, FileName, FilePath,
  MetaDescription, FileSize, Date and so on
• Includes the files a node willing to share
• In QueryHit, a node only sends out FileID to
  its peer. The peer opens a customized FTP/HTTP
  connection to the node and retrieve target files
  by FileID

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Main Loop
Listen for new connection requestGNUTELLA
CONNECT/0.4\n\n
If neighbor table full
N
Spawn a new thread to handle connection
Y
Send GNUTELLA NOT OK\n\nClose connection
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Maintain and Routing

• Process descriptions accordingly
• Ping Response with a Pong withnodes
  information. Update routinghistory table, TTL-1
  and forwardPing to all neighbors if TTLgt0
• Pong Check with routing historytable and if it
  is in, then TTL-1 and forward to its
  destination else discard
• Query Search local file (File Sharing Table),
  if hit, send Query/Hit with FileID and
  otherinfo. Update routing history table,TTL-1
  and forward Queryto all neighbors if TTLgt0
• QueryHit Check with routinghistory table and if
  it is in, thenTTL-1 and forward to
  itsdestination else discard

Re-check if neighbor table full
Put a new entry in NeighborTable Send GNUTELLA
OK\n\n
N
Y
Send GNUTELLA NOT OK\n\nClose
connectionThread ends
Listen for Description Head (23 bytes)
At any stage, if it timeouts or any unexpected
strings are received, the entry in NeighborTable
will be deleted, connection will be closed and
the thread ends