Lisa's PC, at EPFL, receives an IP packet from a server in the US. If we look into the frame that finally reaches Lisa's PC, the source MAC address in its header is the MAC address of ...

All network masks are 255.255.255.0. Which of the following are valid choices for A's IP address ?

Bart's smartphone, at EPFL, receives an IP packet from a server in the US. The IP source address in the packet, seen at Bart's smartphone, is the IP address of ...

We sniff the packets containing a request sent by Bart to a web server. Inside the IP packet header we can read:

An application program at a computer A transfers an object to a computer B over the internet, using TCP. Some data is lost on the way. 

The IP layer uses packet switching rather than message relaying because (we did not discuss this in class, but try to think about it and we will discuss next week)

Lisa's PC sends a request to the EPFL DNS server. We sniff the packet with wireshark at Lisa's PC and find that the destination port number is 53, which is the well known port number for DNS servers; the source port number is 13235. Then the DNS server responds to Lisa's request. We also sniff the response from the DNS server, also at Lisa's PC. What port numbers should we see in the response packet ?