Consider the following figure. Assuming TCP Tahoe is the protocol experiencing the behavior shown above, answer the following questions. In all cases, you should provide a short discussion justifying your answer. 45 40- 35- 30 25- 20- 15- 10- 5- 0 2 4 6 8 10 12 14 16 18 20 22 Transmission round TCP window size as a function of time a) Identify the intervals of time when TCP congestion avoidance is operating. b) What is the value of ssthresh at the 8th transmission round and 20t transmission round, respectively? c) Suppose TCP Reno is used (instead of TCP Reno), and assume that triple duplicate ACKs are received at the 18th round. What are the ssthresh and the congestion window size at the 19th round? Congestion window size (segments)

Consider the following figure. Assuming TCP Tahoe is the protocol experiencing the behavior shown above, answer the following questions. In all cases, you should provide a short discussion justifying your answer. 45 40- 35- 30 25- 20- 15- 10- 5- 0 2 4 6 8 10 12 14 16 18 20 22 Transmission round TCP window size as a function of time a) Identify the intervals of time when TCP congestion avoidance is operating. b) What is the value of ssthresh at the 8th transmission round and 20t transmission round, respectively? c) Suppose TCP Reno is used (instead of TCP Reno), and assume that triple duplicate ACKs are received at the 18th round. What are the ssthresh and the congestion window size at the 19th round? Congestion window size (segments)

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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14 The following figure shows a TCP transaction. Assume Host A always has data to send, and each packet has size 20 Bytes. Assume Host A has a sending window of 40 Bytes, that is, it can send two "in-flight” packets maximum. Answer the following questions. A. At the time marked "1", i.e., when the first packet times out, will Host A send any packet? if your answer is no, explain why not; if your answer is yes, how many packets will be sent, what are the sequence numbers of them? B. At the time marked "2", i.e., when the ACK of the 2nd packet is received by Host A, will Host A send any packet? if your answer is no, explain why not; if your answer is yes, how many packets will be sent, what are the sequence numbers of them? Host A Host B Seq=80, 20 bytes of data Seq=100, 20 bytes of data Xª 1 2- timeout
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?
Below are the two questions, so make sure to answer each part carefully and label the response for each question: 1) Why does TCP implement congestion control if it already has flow control to manage the sender's window? 2) Consider our recent reading [Chiu+89] Analysis of the Increase and Decrease algorithms for congestion avoidance in computer networks. How does this article showcases that TCP is fair?
Suppose the sequence number field on a TCP packet is 46005. The packet carries 102 bytes of (application-layer) data. The TCP header size on this packet is 20 bytes. (a) What is the sequence number of the last application byte contained in the packet above? (b) What is the value of the acknowledgment number field on the ACK that the receiver generates for the packet above? (c) Do you have sufficient information in this question to determine the value of the sequence number field of the ACK packet that the receiver generates for the packet above? If so, what is the sequence number? If not, why not? (d) If the size of the TCP header were larger (e.g., 24 bytes, due to additional TCP options), would your answers to parts (a)–(c) change? Why or why not?
Below are the two questions, so make sure to answer each part carefully: Why does TCP implement congestion control if it already has flow control to manage the sender's window? Consider our recent reading [Chiu+89] Analysis of the Increase and Decrease algorithms for congestion avoidance in computer networks. How does this article showcases that TCP is fair?
1. What is the difference between packet fragmentation (i.e., at network layer) and frame frag- mentation (i.e., at link layer) in terms of purpose? 2. Suppose that host A is connected to a router R1, R1 is connected to another router, R2, and R2 is connected to host B. Suppose that a TCP message that contains 800 bytes of data and 20 bytes of TCP header is passed to the IP function at host A for delivery to B. Show the Total length, DF, MF, and Fragment offset fields of the IP header in each packet transmitted over the three links. (Assume that link A-R1 can support a maximum frame size of 1024 bytes including a 14-byte frame header, link R1-R2 can support a maximum frame size of 512 bytes, including an 8-byte frame header, and link R2-B can support a maximum frame size of 432 bytes including a 12-byte frame header.) (*hint: the Fragment offset field is denominated by 8-bytes, not bytes) 3. What is the purpose of the path MTU discovery process (see textbook Figure 5-42) and why does…
In TCP Vegas, the calculation of Actual Rate is done by dividing the amount of data transmitted in one RTT interval by the length of the RTT. (a) Show that for any TCP, if the window size remains constant, then the amount of data transmitted in one RTT interval is constant once a full window-full is sent. Assume that the sender transmits each segment instantly upon receiving an ACK, packets are not lost and are delivered in order, segments are all the same size, and the first link along the path is not the slowest. (b) Give a timeline sketch showing that the amount of data per RIT above can be less than Congestion Window.
Consider a satellite channel running TCP/IP as shown in the figure below. Due to the long round trip time (RTT) and high bit error rate (BER) the conventional TCP congestion mechanism doesn’t work well in asatellite transmission system. 3.2: Now assume TCP spoofing is implemented in the system. When the TCPsender receives an ACK on behalf of the TCP receiver, does this mean that apacket has been successfully received by the TCP receiver? Explain youranswer in detail.
39. The figure below shows the TCP Congestion Window for various transmission rounds of a TCP connection. 20 18 16 14 12 10 4 2 2 4 6 10 12 14 16 18 20 Transmission Round How many more (or less) segments will TCP Tahoe send compared to TCP Reno between the transmission rounds 12 and 16 inclusive (i.e., t12 to t16) for the same sequence of events as shown in the graph above (i.e., loss events at t11, tl4 and t16)? a. TCP Tahoe send 13 less segments compared to TCP Reno b. TCP Tahoe send 20 more segments compared to TCP Reno c. TCP Tahoe send 13 more segments compared to TCP Reno d. TCP Tahoe send 20 less segments compared to TCP Reno e. TCP Tahoe send 28 less segments compared to TCP Reno Congestion Window (MSS) 00
Consider a long-lived TCP session with an end- to-end bandwidth of 1 Gbps (= 10⁹ bits-per- second). The session starts with a sequence number of 1234. The minimum time (in seconds, rounded to the closest integer) before this sequence number can be used again is
In TCP Fast Retransmit, if we receive three duplicate ACKS after sending out a packet that is not incrementally ACK-ed but before the time-out associated with that packet, we immediately retransmit the packet without waiting for the timeout to occur. Why do we wait for three duplicates instead of just one?
Suppose that a TCP source uses a=0.2 and b=0.25. Further assume that this TCP source has just received three ACKs for which it calculated the following SampleRTT values: 24ms, 31ms, 28ms. What are the latest EstimatedRTT and DevRTT values at this TCP source? Assume that the starting values of EstimatedRTT and DevRTT are 30ms and 3ms, respectively. Also, what is the latest TimeOutInterval at this TCP source? Two-digit precision is sufficient in your calculations.