2. Consider a slotted TDM hierarchical network in which there are 8 computers sharing a 10 Mbps channel to a router R1, sending packets to R1 which must all be forwarded by R1 over an outgoing link (called the MAN link), as shown in Figure 1. Computers A-H always have packets waiting to be sent, so no timeslot on the shared LAN is idle. Ignore the propagation delay on the LAN. The MAN link outgoing from R1 is a 100 Mbps link. The network layer protocol in use has a PDU with exactly 40 bytes of header and exactly 200 bytes of payload (SDU). The DLC layer protocol in use on the LAN has a PDU with exactly 40 bytes of header and 20 bytes of trailer. The DLC layer protocol in use on the outgoing link from R1 has a PDU with 40 bytes of header and no trailer. The physical layer does not impose any bit overhead in either channel. Use 1 Mbps = 1000000 bps.

1. Consider a path from host A to host B through a router X as follows: A- -X-B The capacity of the link AX is denoted Ra, while the capacity of the link XB is denoted Rb in units of [bits/s]. Assume that Ra Ri. Is it possible that the second packet queues at input queue of the second link? Explain. Now suppose that host A sends the second packet T seconds after sending the first packet. How large must T be to ensure no queueing before the second link? Explain.