138) For a 1-Gbps network operating over 4000 km, the delay is the limiting factor, not the bandwidth. Consider a MAN with the average source and destination 20 km apart. At what data rate does the round-trip delay due to the speed of light equal the transmission delay for a1-KB packet

139) A group of 2n - 1 routers are interconnected in a centralised binary tree, with a router at each tree node. Router i communicates with router j by sending a message to the root of the tree. The root then sends the message back down to j. The mean number of hops per message for large n, assuming that all router pairs are equally likely will be

140) Let the clock-driven scheme for generating initial sequence numbers is used with a 15-bit wide clock counter. The clock ticks once every 100 msec, and the maximum pocket lifetime is 60 sec.How often need resynchronization take place when the data consumes 240 sequence numbers/min?