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Recent questions tagged tanenbaum

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Ethernet frames must be at least 64 bytes long to ensure that the transmitter is still going in the event of a collision at the far end of the cable. Fast Ethernet has the same 64-byte minimum frame size but can get the bits out ten times faster. How is it possible to maintain the same minimum frame size?
asked Mar 15, 2019 in Computer Networks ajaysoni1924 128 views
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An IP packet to be transmitted by Ethernet is 60 bytes long, including all its headers. If LLC is not in use, is padding needed in the Ethernet frame, and if so, how many bytes?
asked Mar 15, 2019 in Computer Networks ajaysoni1924 265 views
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Two CSMA/CD stations are each trying to transmit long (multiframe) files. After each frame is sent, they contend for the channel, using the binary exponential backoff algorithm. What is the probability that the contention ends on round k, and what is the mean number of rounds per contention period?
asked Mar 15, 2019 in Computer Networks ajaysoni1924 130 views
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A 1-km-long, 10-Mbps CSMA/CD LAN (not 802.3) has a propagation speed of 200 m/μsec. Repeaters are not allowed in this system. Data frames are 256 bits long, including 32 bits of header, checksum, and other overhead. The first bit slot after a ... the channel in order to send a 32-bit acknowledgement frame. What is the effective data rate, excluding overhead, assuming that there are no collisions?
asked Mar 15, 2019 in Computer Networks ajaysoni1924 87 views
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A seven-story office building has 15 adjacent offices per floor. Each office contains a wall socket for a terminal in the front wall, so the sockets form a rectangular grid in the vertical plane, with a separation of 4 m between sockets, both horizontally and vertically. Assuming ... to connect all sockets using (a) A star configuration with a single router in the middle? (b) A classic 802.3 LAN?
asked Mar 15, 2019 in Computer Networks ajaysoni1924 22 views
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Consider five wireless stations, A, B, C, D, and E. Station A can communicate with all other stations. B can communicate with A, C and E. C can communicate with A, B and D. D can communicate with A, C and E. E can communicate A, D and B. (a) When ... possible? (b) When B is sending to A, what other communications are possible? (c) When B is sending to C, what other communications are possible?
asked Mar 15, 2019 in Computer Networks ajaysoni1924 78 views
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Frames arrive randomly at a 100-Mbps channel for transmission. If the channel is busy when a frame arrives, it waits its turn in a queue. Frame length is exponentially distributed with a mean of 10,000 bits/frame. For each of the following frame arrival rates, give the ... frame, including both queueing time and transmission time. (a) 90 frames/sec. (b) 900 frames/sec. (c) 9000 frames/sec.
asked Mar 15, 2019 in Computer Networks ajaysoni1924 85 views
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What is the length of a contention slot in CSMA/CD for (a) a 2-km twin-lead cable (signal propagation speed is 82% of the signal propagation speed in vacuum)?, and (b) a 40-km multimode fiber optic cable (signal propagation speed is 65% of the signal propagation speed in vacuum)?
asked Mar 15, 2019 in Computer Networks ajaysoni1924 554 views
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A large population of ALOHA users manages to generate 50 requests/sec, including both originals and retransmissions. Time is slotted in units of 40 msec. (a) What is the chance of success on the first attempt? (b) What is the probability of exactly k collisions and then a success? (c) What is the expected number of transmission attempts needed?
asked Mar 15, 2019 in Computer Networks ajaysoni1924 126 views
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A group of N stations share a 56-kbps pure ALOHA channel. Each station outputs a 1000-bit frame on average once every 100 sec, even if the previous one has not yet been sent (e.g., the stations can buffer outgoing frames). What is the maximum value of N?
asked Mar 15, 2019 in Computer Networks ajaysoni1924 177 views
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A bit stream 10011101 is transmitted using the standard CRC method described in the text. The generator polynomial is x ^3 + 1. Suppose that the third bit from the left is inverted during transmission.. Give an example of bit errors in the bit string transmitted that will not be detected by the receiver.
asked Sep 3, 2018 in Computer Networks Na462 159 views
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Ques. A disadvantage of a broadcast subnet is the capacity wasted when multiple hosts attempt to access the channel at the same time. As a simplistic example, suppose that time is divided into discrete slots, with each of the n hosts attempting to use the channel with probability p during each slot. What fraction of the slots are wasted due to collisions? Ans. 1 - np(1-p)n-1 - (1-p)n.
asked Aug 27, 2018 in Computer Networks Na462 105 views
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A 1024-bit message is sent that contains 992 data bits and 32 CRC bits. CRC is com- puted using the IEEE 802 standardized, 32-degree CRC polynomial. For each of the following, explain whether the errors during message transmission will be detected by the receiver: (a) There ... bit long burst error. (f) There was a 35-bit long burst error. In the above question can anyone explain for option (c).
asked May 10, 2018 in Computer Networks Mohanakrrishna Venka 140 views
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How important it is to study the WSClock page replacement algorithm (Given in Tanenbaum OS book) for gate 2019 preparation ? May I leave this topic, and may be later if I get time, should I read it.
asked Apr 10, 2018 in Operating System Harsh Kumar 70 views
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Suppose that the clock-driven scheme for generating initial sequence numbers is used with a 15-bit wide clock counter. The clock ticks once every $100msec$, and the maximum packet lifetime is $60 sec$. How often need resynchronization take place (a) in the worst case? (b) when the data consumes $240$ sequence numbers/min?
asked Nov 25, 2017 in Computer Networks reena_kandari 101 views
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This is a screenshot from tanenbaum my question is, the frame which they are talking about in highlighted text is not an ethernet frame right? as ethernet frame is used in LAN. So which frame they are talking about in here? Is it the frame which is used when we are tansmitting in wireless medium from one network to another?
asked Nov 6, 2017 in Computer Networks Na462 96 views
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Can someone plz explain this highlighted text ? I took it from Tannenbaum. thank you :)
asked Aug 13, 2017 in Computer Networks Pawan Kumar 2 63 views
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A noiseless 4-kHz channel is sampled every 1 msec. What is the maximum data rate? How does the maximum data rate change if the channel is noisy, with a signal-to-noise ratio of 30 dB?
asked Jul 20, 2017 in Computer Networks targate2018 456 views
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what is the difference between connection oriented and connection less services?
asked May 1, 2017 in Computer Networks iarnav 92 views
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A datagram network allows routers to drop packets whenever they need to. The probability of a router discarding a packet is p. Consider the case of a source host connected to the source router, which is connected to the destination router, and then to the destination ... number of (a) hops a packet makes per transmission? (b) transmissions a packet makes? (c) hops required per received packet?
asked Apr 7, 2017 in Computer Networks anonymous 1.2k views
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Compute the fraction of the bandwidth that is wasted on overhead (headers and retransmissions) for protocol 6 on a heavily loaded 50-kbps satellite channel with data frames consisting of 40 header and 3960 data bits. Assume that the signal propagation time from the earth to ... The error rate for data frames is 1%, and the error rate for NAK frames is negligible. The sequence numbers are 8 bits.
asked Apr 1, 2017 in Computer Networks anonymous 90 views
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Consider an error-free 64-kbps satellite channel used to send 512-byte data frames in one direction, with very short acknowledgements coming back the other way. What is the maximum throughput for window sizes of 1, 7, 15, and 127? The earth-satellite propagation time is 270 msec
asked Apr 1, 2017 in Computer Networks anonymous 252 views
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