计算机网络原理第一章习题
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第一章习题
1. What are the two types of services that the Internet Provides to its applications? What are some characteristics of these services?
2. Briefly describe how the Internet’s connection-oriented service provides reliable transport?
3. Suppose that between a sending host and receiving host there is exactly one packet switch. The transmission rates between the sending host and the switch and between the switch and the receiving host rate R1 and R2, respectively. assuming that the router uses store-and-forward packet switching, what is the total end-to-end delay to send a packet of length L (Ignore queuing, propagation delay, and processing delay) ?
4. What are the five layers in the Internet protocol stack? What are the principal responsibilities for each of these layers?
5. This elementary problem begins to explore propagation delay and transmission delay, two central concepts in data networking. Consider two hosts, Host A and B, connected by a single link of rate R bps. Suppose that the two hosts are separated by m meters, and suppose the propagation speed along the link is s meters/sec. Host A is to send a packet of size L bits to Host B.
a. Express the propagation delay, d prop in terms of m and s.
b. Determine the transmission time of the packet, d trans in terms of L and R.
c. Ignoring processing and queuing delays, obtain an expression for the end-to-end delay.
d. Suppose Host A begins to transmit the packet at time t=0. At time t=d trans, where is the last bit of the packet?
e. Suppose d prop is greater than d trans. At time t=dtrans, where is the first bit of the packet?
a.Suppose d prop is less than d trans. At time t=dtrans, where is the first bit of the packet?
f. Suppose s=2.5*108, L=100 bits, and R=28 kbps. Find the distance m so that d prop equals d trans.
6. Consider the queuing delay in a router buffer (Preceding an outbound link) . Suppose all packets are L bits, the transmission rate is R bps, and that N packets arrive to the buffer every LN/R seconds. Find the average queuing delay of a packet.
7. Consider the queuing delay in a router buffer. Let I denote traffic intensity, that is I=La/R. Suppose that the queuing delay takes the form IL/R(I-1) for I<1.
a. Provide a formula for the total delay, that is, the queuing delay plus transmission delay.
b. Plot the total delays as a function of L/R.