NACHOS 3

Networking and encryption

Practical part

We found that nachOS already provides message delivery with this characteristics: ● Unreliable● Has fixed-size● Messages can be dropped

Networking on Nachos

This class is defined in the files post.h and post.cc in the network directory This class is like its name a postoffice or a collection of mailboxes. Here its defined two main operations:

● Send -> send a message to a remote machine

● Receive-> waits for a message in the mailbox In this class are used threads for sending messages and for receiving messages in the mailbox.

PostOffice Class

This class defines the format of the messages that will be sent and received The constructor of this class initialize only one message, by using: ● PacketHeader● MailHeader

Mail Class

Is a part of the message that is put at the begining of the message by the PostOffice before the message is sent. This header contains: ● Destination mailbox address● Number of bytes in the message

MailHeader Class

Defines a single mailbox for receiving messages. Incoming messages are placed by the PostOffice into the mailbox. So the messages can be taken by a thread of the machine that is receiving the message A mailbox is implemented as a list of messages using SynchList object

MailBox

The emulation of a physical network connection is implemented in the files network.h and network.cc in the machine directory. In this file (network.cc) is defined the class PacketHeader, which defines that, a packet header.

Network