The Chewy Center of the Internet

Recall that the count-to-infinity problem in distance vector routing is when a change in the topology causes nodes to form a loop. The nodes break out of the loop only once their costs count high enough to choose a different route.

1. Can decreasing the routing cost of a link cause the count-to-infinity problem?

A. Yes, a decreasing link cost can cause the count-to-infinity problem.

B. No, a decreasing link cost cannot cause the count-to-infinity problem.

2. Can removing a link cause the count-to-infinity problem?

A. Yes, removing a link can cause the count-to-infinity problem

B. No, removing a link cannot cause the count-to-infinity problem

3. Can increasing the routing cost of a link cause the count-to-infinity problem?

A. Yes, increasing the routing cost of a link can cause the count-to-infinity problem.

B. No, increasing the routing cost of a link cannot cause the count--to-infinity problem.

4. Can removing a vertex from the graph cause the count-to-infinity problem?

A. Yes, removing a vertex from the graph can cause the count-to-infinity problem.

B. No, removing a vertex from the graph cannot cause the count-to-infinity problem.

5. Recall that BGP uses a modification of distance vector routing called path vector routing. where route advertisements include the full AS path. Can a router detect some potential routing loops by examining only a path vector?

A. Yes, using only a path vector a router can detect some loops.

B. No, a path vector alone has insufficient information to detect any loops.

6. An AS chooses to route packets for a specific prefix to another AS based on the path this second AS advertised for that prefix. Is it assured that all packets to that prefix will follow that advertised AS path to the destination?

A. Yes, all packets sent to that prefix will traverse the AS path the other AS advertised.

B. No, packets sent to that prefix may traverse a different AS path.

7. AS number 144 has two border routers BR1 and BR2. BR1 peers with AS 555. BR2 peers with AS 1977. BR1 receives a route advertisement from AS 555 for prefix 128.15.0.0/16, with path 78 11101 6294 555 555. The double listing of 555 is correct its a way for 555 to make the path seem longer. Is BR2 required to advertise a route to this prefix to AS 1977?

A. Yes, BR2 is required to advertise a route to AS 1977 for 128.15.0.0/16.

B. No, BR2 is not required to advertise a route to AS 1977 for 128.15.0.0/16.

8. Assuming that BR2 decides to advertise a route to the prefix 128.15.0.0/16, which of the following are valid route advertisements? AS 144 may have received advertisements from other ASes but received no other advertisements for that prefix from AS 555. Check all that are valid.

A.128.15.0.0/16 6294 144

B. 128.15.0.0/16 555 144

C. 128.15.0.0/16 78 11101 6294 555

D. 128.15.0.0/16 78 11101 6294 555 144

E. 128.15.0.0/16 78 11101 6294 555

F. 128.15.0.0/16 78 11101 6294 555 555 144 144

G. 128.15.0.0/16 78 78 144 144

H. 128.15.0.0/16 64393 144 144

9. Which of the following statements are true?

A. Max-min fairness is the only notion of fairness.

B. Max-min fairness always divides link bandwidth equally among flows traversing a network.

C. An allocation of rates to flows that is max-min fair may not maximize the total throughput of flows in the network.

D. In a network with only one router and for which every flow can saturate the bottleneck link on its own, max-min fairness divides link bandwidth equally among flows traversing the bottleneck link.

10. An Internet backbone link between San Francisco (SF) and New York (NY) has a data rate of 1Gb/s and an RTT of 100ms. A TCP flow starts from a host at SF to a receiver at NY. The receivers advertized window is never larger than 1MB. What is the maximum rate achievable by the sender?Which of the following statements are true?

A. ~40Mb/s

B. ~80Mb/s

C. ~98Mb/s

D. ~0.83Gb/s

E. ~980Mb/s

P.S. I don't know why it doesn't have proper spacing. :(