Answer the following problems.
problem 1) Consider the two basic approaches identified toward achieving multicast: unicast emulation and network-layer-multicast. Consider a sender and 32 receivers. Assume that sender is connected to the receiver through a binary tree of routers. What is the cost of sending a multicast packet, in the case of unicast emulation and network-layer multicast, for this topology? Suppose that every time a packet (or a copy of the packet) traverses a link, it incurs a cost C. What topology for interconnecting the senders, receivers, and routers will bring the cost of unicast emulation and network-layer multicast as far apart as possible? You can choose as many routers as you like.
problem 2) As a possible congestion control mechanism in a subnet using virtual circuits internally, a router could refrain from acknowledging a packet until
(i) it knows its last transmission along virtual circuit was received successfully, and
(ii) it has a free buffer.
For simplicity, suppose that routers use a stop-and-wait protocol and that each virtual circuit has one buffer dedicated to it for each direction of traffic. If it takes T seconds to transmit a packet (data or acks) and there are n routers on the path, what is the rate at which packets are delivered to the destination host? Suppose that transmission errors are rare, and the host router connection is infinitely fast.
problem 3) Why does UDP exist? Would it not have been sufficient to let applications send raw IP packets?
problem 4) Consider idealized model for the steady-state dynamics of TCP: the average throughput of connection in the period where the congestion window varies from (W*MSS)/2 to W*MSS is (0.75 * W * MSS)/RTT. In this circumstances, suppose that only one packet is lost at the very end of each period. Demonstrate that the loss rate is equal to L = 1/[ 3/8 * W*W + 3W/4]