Problem 2
A group of \(\mathrm{N}\) stations share a \(56-\mathrm{kbp}\) s pure ALOHA channel. Each station outputs a 1000 -bit frame on average ance every \(100 \mathrm{sec}\), 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?
Problem 3
Consider the delay of pure ALOHA versus slotted ALOHA at low load. Which one is less? explain your answer.
Problem 6
What is the length of a contention slot in CSMALCD for (a) a 2-km twin-lead cable (where signal propagation speed is \(82 \%\) of the signal propagation speed in vacuum)?, and (b) a \(40-k m\) multimode fiber optic cable (signal propagation speed is \(65 \%\) of the signal propagation speed in vacuum)?
Problem 8
In the binary countdown protocol, explain how a lower-numbered slation may be starved from sending a packet.
Problem 10
Sixteen stations, numbered I through 16, are contending for the use of a shared channel by using the adaptive tree-walk protocol. If all the stations whose addresses are prime numbers suddenly become ready at ance, bow many bit slots are needed to resolve the contention?
Problem 11
A group of friends gets togcther to play highly interactive CPU- and network- intensive video games. The friends play together using a high-bandwidth wireless network. The wireless signal cannot propagate through walls, but the friends are all in the same room. In such a setup, would it be best to use nonpersistent CSMA or the token ring protocol? Please explain you answer.
Problem 12
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 \(A\) is sending to \(\mathrm{B}\), what other communications are possible? (b) When IB is sending to A what other communications are possible? (c) When \(\mathrm{B}\) is sendiag to \(\mathrm{C}\), what other coenmunications are possible?
Problem 17
A 1-km-long, 10-Mbps CSMA.CD 1.AN (not \(802.3\) ) has a propagation speed of \(200 \mathrm{~m} / \mathrm{jecc}\). 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 stot after al saccessful transmission is reserved for the receiver to capture the channel in order lo send a 32-bit acknowledyement frame. What is the effective data rate, excluding overhead, assuming that there are no collisaons?
Problem 19
An IP packet to be transmitted by Ethemet 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?
Problem 20
Ethernet frames must be at least 64 bytes long to ensure that the transmiitter 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?
