A user uploads a 4 GB ZIP archive over the Internet to a cloud storage service. The upload runs over TCP rather than UDP.Why is TCP the more natural choice of transport protocol for this upload?

A learning bridge connects three hosts. Host A is on port 1, host B is on port 2 and host C is on port 3. The forwarding table starts empty. Three frames cross the bridge in this order: host A sends a frame to host B, host B sends a frame to host A, and then host C sends a frame to host B.Which hosts receive a copy of the third frame, from host C to host B?

A file transfer application needs every byte to arrive, in order. A video call application needs low delay and tolerates some loss.According to the end-to-end principle, the network core should give both applications the same reliable, in-order delivery.

Figure: AS X and its neighbors (Module 4)Consider AS X and its neighbors. AS C is a customer of AS X. AS Y is a peer of AS X. AS P is a provider of AS X. Each of the three neighbors advertises a route to prefix p to AS X. The route from AS P has the shortest AS path of the three. AS X sets LocalPref according to its business relationship with each neighbor.Which LocalPref values does AS X assign to the three routes?

Figure: An input-queued crossbar with one FIFO queue per input (Module 6)Consider an input-queued crossbar switch where each input port maintains a single FIFO queue. The crossbar is scheduled using the take a ticket scheme.During the current packet time slot:The head-of-line packet at Input A is destined for Output 1.The head-of-line packet at Input B is also destined for Output 1.The scheduler awards Output 1 to Input A.The second packet in queue at Input B is destined for Output 2, which is idle.What packet does Input B transmit during this time slot?

Figure: Multibit trie with a stride of 2 (Module 5)Consider a multibit trie with a stride of 2, so each node reads 2 bits of the address. The trie was built from the following five prefixes, after controlled prefix expansion to lengths 2 and 4:Q11 = 1*Q12 = 10*Q13 = 1011*Q14 = 110*Q15 = 1111*A packet arrives with a destination address that begins with 1110.Which prefix does the search return for this address?

A backbone router carries about 250,000 concurrent flows of short duration. The router keeps a cache of recently seen destination addresses.The cache lets the router skip most lookups in the forwarding table.

A new TCP connection starts in slow start with a congestion window of cwnd = 1 segment. No loss occurs.The congestion window grows by one segment per RTT, so the window reaches 4 segments after three RTTs.

Figure: Transit and peering relationships (Module 4)Consider AS X, which has customers, peers and providers. AS X exports routes according to its business relationships. AS X learns a route to prefix p from one of its customers.To which neighbors does AS X advertise this route?

Figure: Sender S and the leaky bucket at router R (Module 6)Consider a sender S that sends bursty traffic to router R. Every 2 seconds, a burst of 80 packets arrives within 1 millisecond.Router R shapes this traffic with a leaky bucket that holds at most 50 packets and leaks 100 packets per second, one every 10 ms. The bucket is empty when the first burst arrives. Each burst is so short that no packet leaves the bucket while it arrives.The operator of router R wants the bucket to drop no packets. Does this leaky bucket meet that goal?