Integration story

Fresh laptop: DHCP gives IP, mask, gateway, DNS server; ARP finds the gateway's MAC; DNS (UDP 53) resolves the name; TCP 3-way handshake to port 80; HTTP GET → 200 OK. On the way, NAPT rewrites source IP/port, routers do longest-prefix match, frames are rebuilt per hop with CRC, fragments reassemble only at the destination. Cached case: 2 RTT + transmission (+ DNS).

1. NAT · 1 mark

   DNS 6 ms, RTT 20 ms, page transmission 4 ms. Time to receive the page (ms)?

   Write your answer before opening the key.

2. MCQ · 1 mark

   ARP translates:

   1. name → IP address
   2. IP address → MAC address on the LAN
   3. private IP → public IP
   4. port → process
3. MSQ · 1 mark

   Which travel over UDP during a page load?

   1. DNS query
   2. HTTP GET
   3. DHCP request
   4. TCP SYN
4. MCQ · 1 mark

   Which item stays the same from the laptop to the server in a network without NAT?

   1. Source MAC address
   2. Destination IP address
   3. Frame CRC
   4. TTL
5. NAT · 2 marks

   Persistent connection, pipelining, base + 6 objects, RTT 25 ms, DNS 15 ms, transmission ignored. Total ms?

   Write your answer before opening the key.

6. MCQ · 1 mark

   Which mechanism ensures a slow receiver is not overwhelmed during the page download?

   1. Congestion control (cwnd)
   2. Flow control (rwnd)
   3. DNS caching
   4. ARP
7. MCQ · 1 mark

   A DNS reply was lost. Which layer is responsible for asking again?

   1. TCP
   2. The DNS client (application) after a timeout
   3. The data link layer
   4. IP
8. MSQ · 1 mark

   Which happen at every router hop?

   1. A new frame with new MAC addresses
   2. Longest-prefix match on the destination IP
   3. TCP handshake
   4. TTL decremented