A company has a dedicated link of 100 Mbps. Each employee, when online, transmits continuously at 12 Mbps when active, but each user is active only 20 percent of the time. Assume packet switching is used. (a) What is the probability that more than 2 users are

A company has a dedicated link of 100 Mbps. Each employee, when online, transmits continuously at 12 Mbps when active, but each user is active only 20 percent of the time. Assume packet switching is used. (a) What is the probability that more than 2 users are

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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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. If transmission starts at time t=0, how long (in seconds) does it take until Computer B has received the last bit of the complete file transfer?Assume that the switch between link 1 and 2 is a "store-and-forward" switch. Furthermore, assume that processing and queuing delays are negligible and no other stations are using the links.
Suppose users share a 3 Mbps link. Also suppose each user requires 150 kbps when transmitting, but each user transmits only 10 percent of the time. (See the discussion of packet switching versus circuit switching in Section 1.3.) a. When circuit switching is used, how many users can be supported? b. For the remainder of this problem, suppose packet switching is used. Find the probability that a given user is transmitting. c. Suppose there are 120 users. Find the probability that at any given time, exactly n users are transmitting simultaneously. (Hint: Use the binomial distribution.) d. Find the probability that there are 21 or more users transmitting simultaneously.
Given a M/M/1 queue, if the average inter-arrival time is Z seconds, the average packet service time is P, find: a. The probability an arriving packet has to wait in the queue b. The variance (o}) of the inter-arrival time The variance (o) of the packet service time d. The average number of packets in the system (i.e., in the queue + in the NIC) c.
Consider a mobile phone user, Harry is talking to his friend, Ron at Milton Keynes,London. Harry is on the train from King’s Cross Station, London to OxfordUniversity. During his travel to Oxford, there are several base stations along therail networks to provide a cellular coverage (from one cell to another cell), so thatHarry can talk to Ron while he’s on the move. After 45 minutes, the call is suddenlyterminated. How to increase a cell area of 2km2 coverage to a bigger coverage such as10km2 ?
A TCP connection is established through 10 wireless hops in an acoustic underwater ad hoc network. Assume that each hop is 100 meter in the average, acoustic signals travel 1500 meter per second, 10 kilobit data can be sent per second over a link, the source node has one megabyte of data to send, the receiver window size is 64 kilobytes, the maximum segment size is 1 kilobyte and the average processing delay for routing at each node is one millisecond. Assume also that the following segments do not reach the destination: 67, 112, 137. What would be the average utilization of the links for this connection if there is not another communications through them? Explain an alternative approach to increase the bandwidth utilization?
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?
If you are given, that station A wants to transmit packet number 2 according to the sequence and n = 2, at the same time station B wants to transmit packet number 1 and n = 2 Calculate and explain the probability for each station and the probability for collision. Calculate a random backoff time for both stations, in the situation of station B, has priority to transmit
Consider a router that transmits bits onto a transmission medium at the rate of 2 Mbps. Let the link be 3 km in length, and bits propagate through the transmission medium at the speed of (approximately) 3x10^8 meters/sec. What is the transmission delay in seconds to transmit a packet of size 2,0o0 bits onto the link? a. 1x10^-5 seconds O b. .001 seconds с. 1 second d. -4 seconds
We have a 4 km down CSMA / CD channel with a capacity of 10 Mbps. Assume the average negotiablelength of interval is 2 ∗ ∆ and that the propagation rate is 2 ∗ 10^8 m/s, the length of frames that are transmitted is 50B. What is the efficiency of the network? The result should be rounded to 3 decimal places.
Assume that an end-to-end communications system is made up of three networks with date rate in Mbps ρ1, ρ2, and ρ3, respectively. Ignoring the other delay components, what is the total end-to-end delay to transmit a packet size of λ?
Referring to (1–6), consider a communication system with the following values for the different probabilities:(a) Find the probabilities P(Y = 0) and P(Y = 1) at the channel output.(b) Find the probability that a 1 was sent given that a 1 was received.(c) What is the probability that a 0 was sent given that a 1 was received?
A frame of 1200 bytes travel through five switches along the path. Each link has a bandwidth of 100 Mbps, a length of 100 m, and a propagation speed of 2 × 10*8 m/sec. Assuming a queuing and processing delay of 2 ms at each switch, what is the approximate end-to-end delay for this packet?