phase. Connection C,'s RTT is 50 msec and connection C,'s RTT is100 msec. Assume that when the data rate in the link exceeds the link'sspeed, all TCP connections experience data segment loss.a. If both C, and C, at time t, have a congestion window of 10 segments,what are their congestion window sizes after 1000 msec?b. In the long run, will these two connections get the same share of the band-width of the congested link? Explain. P50. Consider a simplified TCP's AIMD algorithm where the congestion windowsize is measured in number of segments, not in bytes. In additive increase, thecongestion window size increases by one segment in each RTT. In multiplica-tive decrease, the congestion window size decreases by half (if the result isnot an integer, round down to the nearest integer). Suppose that two TCPconnections, C, and C,, share a single congested link of speed 30 segmentsper second. Assume that both C, and C, are in the congestion avoidance

phase. Connection C,'s RTT is 50 msec and connection C,'s RTT is 100 msec. Assume that when the data rate in the link exceeds the link's speed, all TCP connections experience data segment loss. a. If both C, and C, at time t, have a congestion window of 10 segments, what are their congestion window sizes after 1000 msec? b. In the long run, will these two connections get the same share of the band- width of the congested link? Explain.

phase. Connection C,'s RTT is 50 msec and connection C,'s RTT is 100 msec. Assume that when the data rate in the link exceeds the link's speed, all TCP connections experience data segment loss. a. If both C, and C, at time t, have a congestion window of 10 segments, what are their congestion window sizes after 1000 msec? b. In the long run, will these two connections get the same share of the band- width of the congested link? Explain.

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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Suppose two TCP connections share a path through a router R. The router's queue size is six segments; each connection has a stable congestion window of three segments. No congestion control is used by these connections. A third TCP connection now is attempted, also through R. The third connection does not use congestion control either. Describe a scenario in which, for at least a while, the third connection gets none of the available bandwidth. and the first two connections proceed with 50% each. Does it matter if the third connection uses slow start? How does full congestion avoidance on the part of the first two connections help solve this? 10:33 am Type a message Dorcon 1 tahir re
Consider a client connecting to a web server via a router as shown in Fig.Q2. Client A sends a request to the server to retrieve a 7.5 Mbytes file. Given that the segment size is 50 Kbytes, the round trip time (RTT) between the server and client is 10 ms, the initial slow-start threshold is 16 and the client's buffer always has a storage space of 1 Mbytes. Assume that TCP Reno is used, there is no loss during transmission and the headers of protocols are ignored. 400 Mbps 200 Mbps 400 Mbps Link a Link b Link c Client Web Server Fig.Q2 (a) Describe how the value of sending window changes as a function of time (in units of RTT) during the whole connection time. 2.
In TCP connection, congestion occurs if the load on the network is greater than the capacity of the network. TCP uses the following algorithm to handle congestion. The algorithm is based on the size of the congestion window (cwnd) which starts with one maximum segment size (MSS). The MSS is determined during connection establishment. At each time the whole window of segments is acknowledged (one transmission), the size of the window grows exponentially. To stop this exponential growth, the sender keeps the track of a threshold. The threshold is set to 16 MSS. After reaching the threshold, the size of the congestion window is increased by 1. After how many transmissions the congestion window size will be 22 MSS?
Consider a modification to TCP's congestion control algorithm. Instead of additive increase, we can use multiplicative increase. A TCP sender increases its window size by a small positive constant a(0
Assume that when establishing a TCP connection, the threshold for the Congestion Window (cwnd) is 1& segments. The congestion control algorithm is TCP Reno. In the oth round, a time out occurs.The ACK packets are then received correctly until the 1 Pth round. In this round, a triple duplicate ack occurs. Then until the 1Sth round, the ack packets are received correctly. Show these steps by plotting (the vertical axis is the congestion window capacity (cwnd) and the horizontal axis is the round number). Also specify the threshold value change each time it occurs. Graph the chart in any software you want and upload the file
3. Consider a simple application-level protocol built on top of UDP that allows a client to retrieve a file from a remote server residing at a well-known address. The client first sends a request with a file name, and the server responds with a sequence of data packets containing different parts of the requested file. To ensure reliability and sequenced delivery, client and server use a stop-and-wait protocol. Ignoring the obvious performance issue, do you see a problem with this protocol? Think carefully about the possibility of processing crashing. State conclusion: Provide Proof: Solution:
Q3.Suppose a client is communication with a server via a TCP Reno connection. The client has sent the data up to sequencenumber 120. The client has received acknowledgment number 80 from the server, and the received window is 50 in the lastmessage received by the client from the server. Moreover, the client has estimated the congestion window as 36 for the server.If the client receives two more acknowledgment number 80, then how much maximum data the client can send to the server?
Consider one TCP connection on a path with a bottleneck link with capacity L. We have a file of size F(assume F is a very large file size). If TCP segment size is B bytes, the two-way propagation delay is tp and connection is always in congestion avoidance phase, find the following: A. Maximum window size that TCP can achieve B. Average window size and average throughput in this TCP connection C. Time it will take from connection establishment to reaching the maximum window size.
Consider a simple congestion-control algorithm that uses linear increase and multiplicative decrease but not slow start, that works in units of packets rather than bytes, and that starts each connection with a congestion window equal to one packet. Give a detailed sketch of this algorithm. Assume the delay is latency only and that when a group of packets is sent only a single ACK is returned. Plot the congestion window as a function of round-trip times for the situation in which the following packets are lost: 9, 25, 30, 38, and 50. For simplicity, assume a perfect timeout mechanism that detects a lost packet exactly 1 RTT after it is transmitted.
Following a timeout occurrence, we considered the possibility of doubling the timeout interval. This method can be thought of as a type of congestion control. The question is why TCP requires a window-based congestion-control method in addition to the doubling-timeoutinterval approach described above.
Suppose a client is communication with a server via a TCP Reno connection. The client has sent the data up to sequence number 120. The client has received acknowledgment number 80 from the server, and the received window is 50 in the last message received by the client from the server. Moreover, the client has estimated the congestion window as 36 for the server. If the client receives two more acknowledgment number 80, then how much maximum data the client can send to the server? Justify your answer via proper references and procedure. (coding required)
Phases of TCP congestion control. Consider the figure below, which plots the evolution of TCP's congestion window at the beginning of each time unit (where the unit of time is equal to the RTT); see Figure 3.53 in the text. In the abstract model for this problem, TCP sends a "flight" of packets of size cwnd at the beginning of each time unit. The result of sending that flight of packets is that either (i) all packets are ACKed at the end of the time unit, (ii) there is a timeout for the first packet, or (iii) there is a triple duplicate ACK for the first packet. At the end of which units of time does TCP detect a triple-duplicate-ACK? Congestion window size (in segments) 40 35 25 20 10 5 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 Time unit (in RTT)