# Recent questions tagged tanenbaum

1
How many frames per second can gigabit Ethernet handle? Think carefully and take into account all the relevant cases. Hint: the fact that it is gigabit Ethernet matters.
2
Some books quote the maximum size of an Ethernet frame as 1522 bytes instead of 1500 bytes. Are they wrong? Explain your answer.
3
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?
4
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?
5
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?
6
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?
7
Sketch the Manchester encoding on a classic Ethernet for the bit stream 0001110101.
8
What is the baud rate of classic 10-Mbps Ethernet?
9
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?
10
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?
11
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.
12
How long does a station, s, have to wait in the worst case before it can start transmitting its frame over a LAN that uses the basic bit-map protocol?
13
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)?
14
In an infinite-population slotted ALOHA system, the mean number of slots a station waits between a collision and a retransmission is 4. Plot the delay versus throughput curve for this system.
15
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?
16
Consider the delay of pure ALOHA versus slotted ALOHA at low load. Which one is less? Explain your answer.
17
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?
18
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.
19
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.
20
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).
1 vote
21
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.
22
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?
1 vote
23
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?
1 vote
24
Can someone plz explain this highlighted text ? I took it from Tannenbaum. thank you :)
1 vote
25
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?
1 vote
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what is the difference between connection oriented and connection less services?