Answer True or False and justify your answer in both cases 1. (2 Points) The only service that DNS provides is the translation of hostnames to IP addresses. 2. (2 Points) DNS uses UDP. If a DNS packet is lost, there is no automatic recovery by UDP, thus application simply retries. 3. (2 Points) IMAP is a mail protocol used for sending mail from sender to recipient. 4. (2 Points) HTTP requires multimedia data to be ASCII encoded. 5. (2 Points) HTTP sends its control information out-of-band. 6. (2 Points) With the selective repeat (SR) protocol, it is possible for the sender to receive an ACK for a packet that falls outside of its current window. 7. (2 Points) With Go-Back-N, it is possible for the sender to receive an ACK for a packet that falls outside of its current window. 8. (2 Points) rdt3.0 receiver FSM (lossy channel with bit errors) can be identical to rdt2.2 receiver FSM (channel with bit errors only, no loss).

rdt_rev (revpkt) && notcorrupt (revpkt) &&has_seq0(revpkt) rdt_rev (revpkt) && (corrupt (revpkt) || has_seql (revpkt)) extract (revpkt, data) deliver_data(data) sndpkt-make_pkt (ACK, 0, checksum) udt_send(sndpkt) C sndpkt-make_pkt (ACK, 1, checksum) udt_send (sndpkt) Wait for 0 from below Wait for 1 from below rdt_rev (revpkt) && notcorrupt (revpkt) &&has_seql (revpkt) extract (revpkt, data) deliver_data(data) sndpkt-make_pkt (ACK, 1, checksum) udt_send(sndpkt) Figure 3.14 rdt2.2 receiver rdt_rev (revpkt) && (corrupt (revpkt) || has_seq0 (revpkt)) sndpkt-make_pkt (ACK, 0, checksum udt_send(sndpkt)