Today super happy, and after-school exercise Self panel discussed the first chapter together with the feeling of flying was so cool.
Next will come and share with you, we discuss the results and simply do a study summary.
12. Consider two hosts A and B are interconnected by a link bandwidth of R (it / s), a length D (m), the signal propagation velocity is V (m / s). Assume that the host A from t = 0, the host starts sending packets to B, the packet length of L bits. Test requirements:
1) the propagation delay (delay) DP;
2) transmission delay dt;
. 3) neglecting the node processing delay and queuing delay, the end to end delay T is the number?
4) If dp> dt, then t = time dt, a first packet where?
5) If V = 250000km / s, L = 512bit, R = 100Mbit / s, so that the delay bandwidth product of exactly one packet length (i.e. 512bit) link length D how many?
answer:
1) dp = L / R (L (bit): the length of the packet; R (bit / s): link bandwidth, i.e., rate)
2) dt = D / V (D (m): the length of the physical link; V (m / s): signal propagation velocity)
3) T = dt + dp (resolved: Since the node ignores processing delay and queuing delay, transmission delay, and so only consider the propagation delay, the positive solution is the sum of both)
4) a first packet: dt * V (resolution: first propagation delay is greater than the given conditions of transmission delays, in general, should be less than the transmission delay propagation delay, in this case here, the transmission time delay can be ignored, then the packet from the beginning of time dt, the first position is dt * V, thereby to obtain the location of the first one.)
5) D = 1280 (interpreted as follows)
13. Assume that the host B to the host A to be stored - send a large file packet-switched forwarding. 3 reaches Host A has a link path segment host B, respectively, the rate R1 = 500kbit / s, R2 = 2Mbit / s, R3 = 1Mbit / s, test requirements:
1) assuming that no other network traffic, the throughput of the file transfer is how much?
2) Assuming that the file size of 4MB, then transfer the file to the host B about how much time?
answer:
1) Thr = 500kbit / s (seek certain formula is as follows: Thr = min (R1, R2, R3 .... Rn))
2) T = 64s (interpreted as follows)
14. Assume that the host L = A sends a packet to the host B 1500B, reaches Host A link segment 3 has a path from host B, the packet switch 2, 3 link segment lengths as D1 = 5000km, D2 = 4000km, D3 = 1000km; link transmission rate of each segment are R = 2Mbit / s, the signal propagation velocity is V = 250000km / s, the packet switch processing delay of each packet is dc = 3ms. Test requirements:
1) In terms of storage - forwarding the packet-switched network, the packet arrival end delay from host A to host B is the number?
2) If dc = 0, and does not take the storage - forwarding the packet-switched each packet, but the packet switch directly forwards received (ie, cut-through switching), then the packet arrives from the host a host B-end delay is the number?
answer:
1) delay is 64ms (Analysis: as packet switching, it is necessary to calculate the delay processing delay nodes have dc, transmission delay dt, well DP propagation delay, because there is only one title group L, it is not involving queuing, calculated without considering the queuing delay.)
2) delay is 58ms (Analysis: Because dc = 0, and only one packet, without regard to queuing delay, propagation delay, and therefore only the transmission delay is calculated to)
1.18 15. The network shown in FIG. A time at t = 0 starts sending a file to the 2Mbit C; B at t = 0.1 + es (e infinitely small positive real number close to 0) sending a file to 1Mbit D. Ignoring propagation delay and processing delay node (Note: k = 3 power of 10, M = 6 10 ^)
Please answer the following questions:
1) If the figure using the network storage - exchange messages forwarded, then A will be delivered 2Mbit files to C B How long will the delivery of documents to 1Mbit D How long??
2) If the network uses the figure storage - forward packet switching, and packet length is equal length 1kbit, and ignore the packet header overhead and removable overhead message, then a will be delivered 2Mbit files to C takes approximately how long B? 1Mbit files will be delivered to D takes approximately how long?
3) packet switching and packet switching compared to what exchange fairer?
