6.3B-5. Multiple Access protocols (5). Consider the figure below, which shows the arrival of 6 messages for transmission at different multiple access wireless nodes at times t=0.1, 0.8, 1.35, 2.6, 3.9, 4.2. Each transmission requires exactly one time unit. t=0.0 C U 1 N 3 4 5 2 3 For the CSMA/CD protocol (with collision detection), indicate which packets are successfully transmitted. You should assume that it takes .2 time units for a signal to propagate from one node to each of the other nodes. You can assume that if a packet experiences a collision or senses the channel busy and that that node will not attempt a retransmission of that packet until sometime after t=5. If a node senses a collision, it stops transmitting immediately (although it will still take .2 time units for the last transmitted bit to propagate to all other nodes). Hint: consider propagation times carefully here. Hint: consider propagation times carefully here. 6 t-1.0 t=2.0 4 t=3.0 5 6 t=4.0 t=5.0

6.3B-5. Multiple Access protocols (5). Consider the figure below, which shows the arrival of 6 messages for transmission at different multiple access wireless nodes at times t=0.1, 0.8, 1.35, 2.6, 3.9, 4.2. Each transmission requires exactly one time unit. t=0.0 C U 1 N 3 4 5 2 3 For the CSMA/CD protocol (with collision detection), indicate which packets are successfully transmitted. You should assume that it takes .2 time units for a signal to propagate from one node to each of the other nodes. You can assume that if a packet experiences a collision or senses the channel busy and that that node will not attempt a retransmission of that packet until sometime after t=5. If a node senses a collision, it stops transmitting immediately (although it will still take .2 time units for the last transmitted bit to propagate to all other nodes). Hint: consider propagation times carefully here. Hint: consider propagation times carefully here. 6 t-1.0 t=2.0 4 t=3.0 5 6 t=4.0 t=5.0

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

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. Consider a packet of length L that begins at end system A and travels over three links to a destination end system. These three links are connected by two packet switches. Let di, si, and Ridenote the length, propagation speed, and the transmission rate of link i, for i=1,2,3. The packet switch delays each packet by dproc. Assuming no queuing delays, in terms of di, si, Ri, (i=1,2,3), and L, what is the total end-to-end delay for the packet? Suppose now the packet is 1,500 bytes, the propagation speed on all three links is 2.5-108m/s, the transmission rates of all three links are 2 Mbps, the packet switch processing delay is 3 msec, the length of the first link is 5,000 km, the length of the second link is 4,000 km, and the length of the last link is 1,000 km. For these values, what is the end-to-end delay?
Consider a reliable data transfer protocol that uses only negative acknowledgements (NAKS). (a) Suppose the sender sends data only infrequently. Would a NAK-only protocol be prefer- able to a protocol that uses ACKS? Explain. (b) Now suppose the sender has a lot of data to send and the end-to-end connection expe- riences few losses. In this case, would a NAK-only protocol be preferable to a protocol that uses ACKS? Explain.
15. Consider the following plot of TCP window size as a function of time (y axis is the congestion window size (segments), and x axis is the transmission round). Assuming that TCP Reno is the protocol experiencing the behavior shown above, answer the following questions. 18 16 14 12 10 00 8 6 4 2 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 1) Identify the intervals of time when TCP slow start is operating. 2) After the 5th transmission round, is segment loss detected by a triple duplicate ACK or by a timeout? 3) What is the value of Threshold at the 7th transmission round? 4) What is the value of Threshold at the 15th transmission round?
6.3A-1. Multiple Access protocols (1). Consider the figure below, which shows the arrival of 6 messages for transmission at different multiple access wireless nodes at times t=0.1, 1.4, 1.8, 3.2, 3.3, 4.1. Each transmission requires exactly one time unit. t=0.0 O o 1 O o 1 2 3 For the pure ALOHA protocol, indicate which packets are successfully transmitted. You can assume that if a packet experiences a collision, a node will not attempt a retransmission of that packet until sometime after t=5. 4 5 t=1.0 9 2 t=2.0 45 t=3.0 6 t=4.0 t=5.0
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. B D E F G H R1 R2 Figure 1 (a) What is the transmission delay of a bit for Computer A? (b) What is the transmission delay of a DLC PDU for…
Consider a two-link network where Host A is connected to the router by a 1 Mbps link with 10 ms propagation delay and the router is connected to Host B by a 15 Mbps link with a 25 ms propagation delay. Host A sends a 1500-byte packet to Host B. What is the transmission delay (in ms) of the packet from the router to Host B?
6.3B-4. Multiple Access protocols (4). Consider the figure below, which shows the arrival of 6 messages for transmission at different multiple access wireless nodes at times t=0.1, 0.8, 1.35, 2.6, 3.9, 4.2. Each transmission requires exactly one time unit. t=0.0 1 U r 1 U 3 2 4 Again consider the CSMA protocol (without collision detection), indicate those packets where the channel is sensed busy and therefore, under CSMA, that message transmission is not attempted. [Again, you should assume that it takes .2 time units for a signal to propagate from one node to each of the other nodes. You can assume that if a packet experiences a collision or senses the channel busy and that that node will not attempt a retransmission of that packet until sometime after t=5. Hint: consider propagation times carefully here]. 5 2 3 a t=1.0 t=2.0 4 t=3.0 56 t=4.0 t=5.0
6.3B-5. Multiple Access protocols (5). Consider the figure below, which shows the arrival of 6 messages for transmission at different multiple access wireless nodes at times t=0.1, 0.8, 1.35, 2.6, 3.9, 4.2. Each transmission requires exactly one time unit. t=0.0 n [ 2 3 t=1.0 4 t=2.0 4 For the CSMA/CD protocol (with collision detection), indicate which packets are successfully transmitted. You should assume that it takes .2 time units for a signal to propagate from one node to each of the other nodes. You can assume that if a packet experiences a collision or senses the channel busy and that that node will not attempt a retransmission of that packet until sometime after t=5. If a node senses a collision, it stops transmitting immediately (although it will still take .2 time units for the last transmitted bit to propagate to all other nodes). Hint: consider propagation times carefully here. Hint: consider propagation times carefully here. t=3.0 5 6 t=4.0 t=5.0