CS415 Minithreads Project 4 Overview

1
CS415 Minithreads Project 4 Overview

• Adrian Bozdog (Adi)
• adrianb_at_cs.cornell.edu

2
What you have to do

• Implement connection-based reliable communication
• IP-like/UDP-like/TCP-like protocol
• Based on the previous implementation
• Correct implementation
• Window size may be one (one packet in transit)
• An application message can have any size (not
  limited by max network datagram size)

3
Reliable communication

• Set up a connection
• Packets sent from specific local ports belong to
  the connection
• Use the connection to send/receive the messages
• Do not use miniport structures
• Use minisocket structures
• Close the connection

4
TCP-like protocol

• Every packet must be acknowledged by the receiver
• Ordered packet delivery
• The sender resends a packet
• After a specific timeout
• If it does not receive an ack
• Implements a handshaking protocol to open a
  connection
• The client sends an open connection packet to the
  server
• The server sends an open connection ACK to the
  client
• The client sends back an ACK to the server

5
TCP implementation details

• You should cope with packet duplicates
• Receiver must
• Keep track of received packets
• Suppress duplicates of received packets
• Sender must
• Suppress duplicates of received ACKs
• Specific scheme for retransmissions and timeouts
  (see project description)
• Sender stops sending a packet after 12.7 seconds
  (after 7 retransmissions)

6
Stream-oriented protocol

• A sender may send a message of any size
• The sender side fragments large messages into
  several packets
• Packet size lt MAX_NETWORK_PKT_SIZE
• Do not preserve message boundaries at the
  receiver
• Receiver side is not required to wait for all
  pieces of the message
• See project description

7
Implementation hints

• Modular-like implementation
• Do not mix the code for TCP-like protocol and the
  code for UDP-like protocol in the same function
• Protocols should communicate only using API
  defined in header files
• TCP-like protocol will use UDP-like protocol
  functionalities (send and receive functions)
• Any protocol may add its header to a message
  (minimsg and minisocket headers)

8
Implementation hints (2)

• UDP protocol (minimsg.c) must distinguish the
  type of communication
• Uses an extra field (type) in its header
• Define a function in minimsg that will be used to
  send packets for all types of communication (do
  not change API provided e.g minimsg_send
  declaration)
• Minimsg_send will use the new defined function to
  send a packet
• A control packet used by the TCP-protocol is not
  received by the application
• Minithread system
• uses a function provided by the TCP-protocol to
  process the control packet
• Does not store the control packet to a port
• Read hints from the project description

9
Compilation hints

• Minimsg.h is modified a little bit to avoid
  circular including (use it to compile the code
  properly)
• Compile the code for Jornada
• Set the two environment variables on the desktop
  that compile Jornada code (set it once for the
  entire semester)
• Read tips for compiling and running programs on
  Jornada (see web site)

10
(No Transcript)