CS415 Minithreads Project 4 Overview

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CS415 Minithreads Project 4 Overview

• Manpreet Singh
• manpreet_at_cs.cornell.edu

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What you have to do

• Implement unreliable communication
• Simulate IP/UDP protocol
• No UDP check-sum
• No UDP fragmentation
• There is an IP layer that sends and receives
  messages (see network.c)

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Networking pseudo-device (1)

• It allows communication between minithreads
  systems
• Does not control which thread processes a
  received packet
• Interrupt-driven implementation
• Network_handler
• executed for each received packet
• Uses the stack of the current thread
• It should finish as soon as possible
• Initialized using network_initialize function

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Networking pseudo-device (2)

• Network_handler receives a structure
• typedef struct
• network_address_t addr - sender
• char bufferMAX_NETWORK_PKT_SIZE - the body
  of entire message
• int size - the length of the entire message
• network_interrupt_arg_t
• Call Network_initialize function
• After clock_initialize()
• Before enabling interrupts and running threads

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Networking functions

• Network_send_pkt sends a packet
• Destination
• Header (body, length)
• Data (body,length)
• Header
• Extra information
• About the sender
• About the receiver
• As small as possible

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Minimsg Layer

• Identifies the end-points of the communication
  (ports)
• The sender assembles the header used to
  identifies the endpoints
• The receiver
• examines the header
• Identifies destination
• Enqueues the packet in the right place

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Minimsg Functions

• Minimsg_send
• Non-blocking
• Parameters
• local and remote ports
• The message and its length
• Appends the header to the message
• Sends the entire data using network_send
• Minimsg_receive
• Blocks the thread until it receives a message on
  the specified port
• Receives information about the remote port used
  to reply

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Miniports

• Data structures that represents endpoints
• Local ports
• Usually, used for listening
• Remote ports
• Created when a packet is received
• Bound to a sending remote port
• Allows the receiver to reply

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Miniports Example

• Ports 2,3 local ports
• A,B - Threads
• Sender A sends a message to Receiver B

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Miniports Example

• Creates the remote port 100
• B receives the message
• Minithreads system creates the remote port 100

Sender
Receiver
2
3
B
A
100
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Miniports Example

• B replies to A
• B uses the remote port as the destination of the
  message the message is relayed to the sending
  port

Sender
Receiver
2
3
B
A
100
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Miniports hints

• Local communication
• Be aware of miniport_destroy function called by
  the receiver
• Remote_miniport pointer to the local port
• Miniport_send implemented based on the remote
  port
• Miniports
• Identified by numbers
• Assigned them successive numbers
• Local miniports starts from 0
• Remote miniports starts from 32768

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Implementation hints

• Do not add unnecessary data to the header (ex
  header length)
• Include the address of the sender (used by the
  routing protocol later)
• Port operations must be O(1)
• Do not waste resources
• Remote miniports are destroyed by the application
• Build other test cases
• Network_initialize returns the ip address of the
  machine
• Due Date October 20, 6 pm