Denne uken skal vi ta for oss litt mer avanserte servere, som kan håndtere flere forbindelser samtidig. Vi ser nærmere på fork- og select-baserte servere, med eksempler.
The applications running on your computer can only send messages to applications running on another computer when the Internet address of that computer is known. We prefer to use names instead of these addresses, e.g. the name fimm.ifi.uio.no instead of the address 129.240.65.205, but sometimes we need the address. You can use the programs host and nslookup to find names for addresses and addresses for names. If they are not installed on your computer, log in to login.ifi.uio.no to test the commands. What interesting things do you find out when you try, for example, www.ifi.uio.no and login.ifi.uio.no?
When you program distributed applications, your programs will usually use the services of the transport layer. The layer makes use of the lower layers, including the network layer, The program traceroute (often /sbin/traceroute) can be used to show you the path that messages from your computer to another computers take. To do this, it lists the names and addresses of the routers between the two end systems.
How many routers are used to forward packets to www.ifi.uio.no, www.uio.no, www.usit.no, www.ntnu.no, www.kth.se, www.fokus.gmd.de, www.cmu.edu?
Which other information does traceroute give you? (check the man pages)
Why are network functions organized in layers?
- Which layers do we distinguish in the Internet?
- What are the tasks of these layers?
- Which additional layers exist in the OSI model?
- What additional services do they offer?
- How are these services offered in the Internet?
How would you characterize the differences between circuit switching and packet switching?
Each unit on one layer of the protocol stack adds a header to messages that are sent to another unit of the same layer.
- Why is this necessary?
- Why is it typical to add it at the front of the packet?