Consider your laptop (source) is connected to YouTube's server (destination) while you are watching a video. Assume that the route between your laptop and the server is 10 hops long as shown below -

Laptop---x1---x2---x3---x4---x5---x6---x7---x8---x9---Server

Consider an IP packet going from source (laptop) to destination (server). .

a. Assume that all x1 to x9 devices are layer-3 routers. How many times the IP header is added or removed on the route from the source to the destination? Where?

b. Assume that all x1 to x9 devices are layer-3 routers. How many times the IP header is modified on the route from the source to the destination? Where?

c. Assume that all x1 to x9 devices are layer-3 routers. How many times the TCP header is added or removed on the route from the source to the destination? where?

d. Assume that x1 is a NAT box, and x2 to x9 are layer-3 routers. How many times the TCP header is modified on the route from the source to the destination? Where?

e. Assume that x1 and x9 are layer-2 switches, and x2 to x8 are layer-3 routers. How many times the link layer header is removed and/or added on the route from the source to the destination? Where?

f. Assume that all x1 to x9 devices are layer-3 routers. Assume the IP packet is lost while going from x3 to x4. Who will retransmit the packet? Where?