CAN Implementation Proxy Module

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CAN Implementation Proxy Module

• Qun Cao
• October 14, 2002

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CAN Infrastructure
Replicate Manager
Message
Message Dispatcher
Node Manager
Lookup result
Content Manager
PROXY
PROXY
DB
Message
Communication Engine
Routing Manager
Next Node
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Proxy Module

• The Role of Proxy
• - Proxy plays as the bridge between CAN
  nodes to client. The CAN internal structure is
  transparent to client. Proxy serves as a web
  service to the client.
• - Proxy collects information from client
  and make a CAN message package for the usage of
  other CAN modules.

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Proxy API

• namespace MyCAN public class Proxy
• public Proxy() public bool
  AddContent (string Key, byte value)
• public byte GetContent(string key)
  
• public bool DeleteContent(string key)
  

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CAN Internal Message

• Works as the standard message flowing between CAN
  modules, carries all the information of client
  request, generated by Proxy Module.
• Structure
• a.l arbitrary length. If an item is a.l, we
  use the first 4 bytes to store its length and
  followed by its content.

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Message Format

• MsgType (4 bytes) The message dispatcher
  dispatches this message to the appropriate module
  in term of MsgType. All content-related messages
  have MsgType1.
• OP (4 bytes) Content manager uses this type to
  perform add, delete, and lookup operations. We
  define
• OP Operations
• 1 Add a piece of content
• 2 Delete a piece of content
• 3 Lookup a piece of content

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Message Format

• P (20 bytes) P SHA(key).
•  
• Key (a.l) a string with arbitrary length. Its
  used in add, delete and lookup a piece of
  content.
•  
• SrcIP (4 bytes) the IP address of the proxy
  instance who issues the message.
•  
• SrcMsgChannel (20 bytes) The message channel
  where this proxy instance receives messages.
  Other CAN nodes who receive this message may use
  the SrcIP and SrcMsgChannel to send messages back
  to this particular proxy instance.
• SrcMsgChannel is generated by some UUID
  generation algorithm.
• Value (a.l) a byte array containing the value of
  a piece of content.

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Pseudo Code - AddContent

• byte20 UUIDUUIDgen()
• byte20 p SHA(key)
• packing message SendMsg(buf,
  IP, 1)
• bool reply RecvMsg(UUID)
• return reply(T/F)

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Pseudo Code - GetContent

• byte20 UUIDUUIDgen()
• byte20 p SHA(key)
• packing message SendMsg(buf,
  IP, 1)
• bool reply RecvMsg(UUID)
• return reply(T/F)

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Pseudo Code - DeleteContent

• byte20 UUIDUUIDgen()
• byte20 p SHA(key)
• packing message SendMsg(buf,
  IP, 1)
• byte buf RecvMsg(UUID)
• parse buf
• return content

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Return Message Format

• The operation result message issued from CAN
  nodes to Proxy
• Structure
• OP ResultCode Description value
• OP (4 bytes) It has the same meaning as the
  above OP.
• ResultCode (1 byte) 1 indicates the
  operation succeeds. 0 indicates it fails.
• Description (a.l) A description string to
  the result code. For example, if ResultCode is
  0, this string describes the error in detail.
• Value (a.l.) The value for the key, if OP
  is 3.