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Phase 4: Network

Phase 4: Network. For ACM05, By Mu LI. The Goal. Implement a full-duplex, reliable, byte-stream communication with no size limits. Write a chat-room program to test your codes. The network layer of nachos. IP Address  LinkAddress Port Number  Port Number

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Phase 4: Network

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  1. Phase 4: Network For ACM05, By Mu LI

  2. The Goal • Implement a full-duplex, reliable, byte-stream communication with no size limits. • Write a chat-room program to test your codes.

  3. The network layer of nachos • IP Address  LinkAddress • Port Number  Port Number • UDP  Embedded in Machine.NetworkLink • UDP Packet  Machine.Packet • TCP  Embedded in the Network Package • TCP Packet  Network.MailMessage • TCP Network Daemon  Network.PostOffice • TCP Socket  Tuple of (SrcLinkAddr, DestLinkAddr, SrcPort, DestPort)

  4. A Graphic Example Provided

  5. Codes provided • machine.NetworkLink.java – provides ordered, unreliable, transmission of limits size packets between nodes • machine.Packet.java – transmission unit

  6. Your work • Define the message formats over Packet.java • Design a socket states transition table

  7. A sample format • The control bit (FIN, …) take one bit, resp. and is in effect when 1 • Blank is just for keeping regular

  8. Message Types • The message is the type iff all correspond control bits are 1 and the others are 0

  9. The states for socket

  10. The Events Cause Transition

  11. States Transition Table

  12. Class: MailMessage • 持有其所对应的machine.Packet格式的对象packet • 发送时使用NetworkLink.send()发送packet • 重载hashcode()使得其与对应的packet有相同的hash，以便查找

  13. Class: Socket • Socket类保存一个端对端的全双工通讯的信息 • Socket类继承自machine.Openfile

  14. Socket.Read() • 从接收缓冲队列receiveBuffer中读取字节，无等待的返回实际读到的字节数 • receiveBuffer中消息按照先后顺序存放至多16个MailMessage，顺序是PostOffice保证的

  15. Socket.Write() • 将所需要写的字节分割打包成MailMessage • 列队入发送窗口队列sendWindow • 当sendWindow满了时，列队入发送缓冲队列sendBuffer

  16. Class: PostOffice • PostOffice类是实现状态转移的核心类，它管理所有的消息的发送与接受，维护所有的socket状态 • 运行时候只有一个实例，内部维护5条进程: • 处理中断的receiveHandler和sendHandler • 收发消息的receiveThread和sendThread • 定时启动发送消息的timeoutThread

  17. Class: NetProcess • 主要任务是处理两个新的sysvcall： • syscallConnect • 首先新建相应的socket，将socket加入进程的descriptor table和PostOffice的socket table。然后维护socket状态，发送SYN，一直等待收到SYN/ACK才返回 • syscallAccept • 取出SYN，根据消息取出对应的socket，将socket放入进程的descriptor table，维护socket状态

  18. Thank you • Q & A

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