Suppose we need to design a stop-and-wait, reliable data transfer protocol between a sender A and a receiver B, over a direct link with the following characteris . The channel from A to B is unreliable and can lose packets. . The channel from B to A is reliable. . Neither channel will corrupt a packet (if a packet is received, it must be correct). . Neither channel will reorder packets. • The maximum RTT between A and B is known and is guaranteed to be D. For each of the following techniques for building reliable data transfer protocol, please match on whether or not, it is needed in the design of the protocol. Acknowledgement Choose... + Negative Acknowledgement Choose... + Sequence Number Choose... →

Suppose we need to design a stop-and-wait, reliable data transfer protocol between a sender A and a receiver B, over a direct link with the following characteris . The channel from A to B is unreliable and can lose packets. . The channel from B to A is reliable. . Neither channel will corrupt a packet (if a packet is received, it must be correct). . Neither channel will reorder packets. • The maximum RTT between A and B is known and is guaranteed to be D. For each of the following techniques for building reliable data transfer protocol, please match on whether or not, it is needed in the design of the protocol. Acknowledgement Choose... + Negative Acknowledgement Choose... + Sequence Number Choose... →

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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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.
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 d, s, and R denotes the length, propagation speed, and the transmission rate of link i, for i=1,2,3 . The packet switch delays each packet by d . Assuming no queuing delays, in terms of d, s , R, (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, and the propagation speed on all three links are 3125km/sec, 10000 km/sec, and 3333km/sec respectively. 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? In the above problem, suppose R1=R2=R3=R and dproc=0. Further, suppose the packet switch does not store-and-forward packets but…
Consider the following network with given line speeds and lengths: Assume the speed of light is 2×10^8 m/s, and that the processing and queuing delays are negligible. Node A sends a 1400-byte frame to node C through node B. Suppose Node A starts sending the first bit of the frame at t=0. Answer the following questions: a. At what time (t=?) node B receives the frame in full (i.e. the last bit)? b. After node B receives the frame in full, then it will start sending the frame to node C. Determine the time (t=?) when node C receives the frame in full. c. Suppose at this time node C sends a small acknowledgment back to node A. The transmission time for the acknowledgment is negligible. Calculate at what times (t=?) the acknowledgment arrives at nodes B and A. d. Assume after sending its frame, node A wait for the acknowledgment back from node C before sending the next frame. What is the average throughput (number of transmitted bits per second) of the data flow from node A to…
Segments are transmitted using GO-BACK-N ARQ over a link with RTT= 6 milliseconds with 17 Mbps transmission rate. The packet size is 3721 bytes and the window size is (static) 449. Assume there is no transmission errors and we always have data to send. Then, the link utilization is 66 x %. Note: provide a number greater without any signs.
Consider a simple protocol for transferring files over a link. After some initial negotiation, A sends data packets of size 1 KB to B; B then replies with an acknowledgment. A always waits for each ACK before sending the next data packet; this is known as stop-and-wait. Packets that are overdue are presumed lost and are retransmitted. (a) In the absence of any packet losses or duplications, explain why it is not necessary to include any "sequence number" data in the packet headers. (b) Suppose that the link can lose occasional packets, but that packets that do arrive always arrive in the order sent. Is a 2-bit sequence number (that is, N mod 4) enough for A and B to detect and resend any lost packets? Is a 1-bit sequence number enough? (c) Now suppose that the link can deliver out of order and that sometimes a packet can be delivered as much as 1 minute after subsequent packets. How does this change the sequence number requirements?
Computer A is sending a 10 MByte long file to Computer B via packet-switching over two consecutive 100 Mbps links of 2000 km length each.Assume that the signal propagation speed on both links is 2 x 108 m/s.Furthermore, assume that the maximum length of a packet is 1480 bytes and that Computer A fills each packet to the max, if possible. How long (in seconds) does it take Computer A to send out one packet of maximum length on the first link?
Computer A is sending a 100 kByte long file to Computer B via packet-switching over two consecutive 10 Mbps links of 1000 km length each.Assume that the signal propagation speed on both links is 2.5 x 108 m/s.Furthermore, assume that the maximum length of a packet is 1500 bytes and that Computer A fills each packet to the max, if possible. How long (in seconds) does it take Computer A to send out one packet of maximum length on the first link?
In this problem you will be doing some elementary calculations of transmission and propagation delays. Consider two hosts, A and B that are connected by a transmissions link of2.1 Mbps. Assume that packets are of length 2.0 Kb (Kilobits) and the length of the link is 100Km. Suppose now that that length of the link is doubled. What is the propagation delay from A to B now and what is the transmission time?
Compare GBN, SR, and TCP (no delayed ACK). Assume that the timeout values for all three protocols are sufficiently long such that 5 consecutive data segments and their corresponding ACKs can be received (if not lost in the channel) by the receiving host (Host B) and the sending host (Host A) respectively. Suppose Host A sends 5 data segments to Host B, and the 3rd segment (sent from A) is lost. In the end, all 5 data segments have been correctly received by Host B. How many segments has Host A sent in total and how many ACKs has Host B sent in total? What are their sequence numbers? Answer this question for all three protocols. The previous expert did the wrong question and the answer was incorrect. The 3rd packet is lost not the 2nd packet
hdet b) Consider sending a packet contains 1100 bits from Host A to Host B in a store and forward nerwork. There are 10 links (and 9 routers) between A and B, and the links are congested (there Is a queuing delays). Assume propagation delay over the links are negligible. As a packet travels along the route, it encounters an average of 5 packets already waiting in the queue to be transmitted when it arrives at each router, How long does it take for the packet to get to the receiver if the nodes transmit on a "first come first served" basis (in ms)?
Suppose A is connected to B via an intermediate router R, as in the previous problem. The A-R link is instantaneous, but the R–B link transmits only one packet each second, one at a time (so two packets take 2 seconds). Assume A sends to B using the sliding window protocol with SWS = 4. For Time = 0, 1, 2, 3, 4, state what packets arrive at and are sent from A and B. How large does the queue at R grow?
To ensure the quality of service, especially for multiple applications, regulating the rate at which packets are sent to the network is an important strategy. The leaky bucket is just one of such mechanisms. A flow of packets is said to conform to the leaky bucket specification (r, b), where r is the average rate and b is the burst rate, if the number of packets arriving at the leaky bucket is less than r*t + b in every time interval of t. What is the implication of that? What will happen if the number of packets arriving at the leaky bucket is equal to or greater than r*t + b?