1. TCP-Unfriendly.TCPs congestion control mechanism relies on users to respond appropriately to network congestion by backing off their sending rate. One potential problem with this mechanism is whats called (by economists) the tragedy of the commons. Suppose Alice knows that everyone else obeys TCPs congestion control mechanism. Then if she continues sending at the same rate, ignoring congestion control, everyone else will slow down a little bit more and she will get better service from the network. So Alice has no motivation to obey TCP congestion control(other than the fact that not doing so involves finding or writing her own TCP stack -details,details) and in fact neither does anyone else. But if no one obeys the mechanism, the network(commons) becomes useless,a tragedy.

(a - 10 pts) Bob the Network Builder has an idea about how to solve this problem. He reasons that congested routers can see the exact state of a TCP connection. So if a particular connection does not slow down in response to dropped packets, or speeds up its sending rate too quickly,the router can send a RST packet to the host that is not obeying the Additive Increase, Multiplicative Decrease rules. This will cause the connection to close, much more painful than just dropping an odd packet or two. From a security standpoint, whats the problem with Bobs idea that is, if Im an adversary intent on sending at a high rate, can I circumvent this mechanism? Are there adjustments to this mechanism that might limit the number of instances where your attack is viable?