CS415 Minithreads Project 4 Overview

1. CS415 Minithreads Project 4 Overview Adrian Bozdog (Adi) adrianb@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 =< 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. User application TCP-like protocol UDP-like protocol Network 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)