Problem 3 Consider the problem of deciding whether to implement a virtual- circuit or a datagram network. Assume a network protocol that allows the system to operate as either a virtual circuit network or a datagram network. That is, its packet header format is specified such that it incorporates both a VCI (Virtual Circuit Identifier) and an arbitrary source/destination addresses. When operating as a virtual circuit, it requires a 4-byte header. When operating as a datagram network, it requires a 40-byte header. Assume that there are 4 hops from source to destination, and that a set up or tear down request packet is 80 bytes (including the header). The total message length is 4096 bytes, the data rate is 9600 bps on all links and the packet size is 256 bytes (including the header). i) If we operate in the datagram mode, how long does it take for the first packet to reach the destination? If we operate in virtual-circuit mode, how long does it take for the first packet to reach the destination? Compute the end-to-end delay for datagram transmission? Compute the transmission? ii) iii) iv) end-to-end delay for virtual-circuit

In modern packet-switched networks, including the Internet, the source host segments long, application-layer messages (for example, an image or a music file) into smaller packets and sends the packets into the network. The receiver then reassembles the packets back into the original message. We refer to this process as message segmentation. Figure 1.27 illustrates the end-to-end transport of a message with and without message segmentation. Consider a message that is 8. 106 bits long that is to be sent from source to destination in Figure 1.27. Suppose each link in the figure is 2 Mbps. Ignore propagation, queuing, and processing delays. a. Consider sending the message from source to destination without message segmentation. How long does it take to move the message from the source host to the first packet switch? Keeping in mind that each switch uses store-and-forward packet switching, what is the total time to move the message from source host to destination host? b. Now suppose that…

Consider a TCP connection with the following parameters:  a) Initial ssthreshold = 8 b) Round Trip Time (RTT) = 10 milliseconds c) Retransmission Timeout period = 40 milliseconds d) Segment size = 2700 bytes The TCP connection was used to transfer 19 data segments, numbered 1 through 19. While sending the segments, data segment 10 was lost the first time it was sent (but arrived at the receiver properly upon being retransmitted). There were no other segment losses apart from the aforementioned. Assume that data segments received out-of-order are buffered at the receiver. What is the average throughput obtained in sending all the data segments (in bytes/sec)? Draw a diagram to show the transmission of the segments in detail.

TCP congestion control example. Consider the figure below, where a TCP sender sends 8 TCP segments at t = 1, 2, 3, 4, 5, 6, 7, 8. Suppose the initial value of the sequence number is 0 and every segment sent to the receiver each contains 100 bytes. The delay between the sender and receiver is 5 time units, and so the first segment arrives at the receiver at t = 6. The ACKs sent by the receiver at t = 6, 7, 8, 10, 11, 12 are shown. The TCP segments (if any) sent by the sender at t = 11, 13, 15, 16, 17, 18 are not shown. The segment sent at t=4 is lost, as is the ACK segment sent at t=7. TCP sender t=1 T t=2 t=3 t=4+ t=5- t=6+ t=11 t=12 t=13 t=14 t=15 t=16 t=17 t=18 I data segment data segment data segment data segment data segment data segment data segment data segment ACK ACK ACK ACK ACK ACK Ty A A V V htt TCP receiver t=6 t=7 t=8 t=9 t=10 t=11 t=12 t=13 What does the sender do at t=17? You can assume for this question that no timeouts have occurred.