请教一下下面二组组题 可以解说一下吗 还有算式 谢谢 有点长@@ =========================================================================== 1 In this problem we consider sending voice from host A to host B over a packet-switched network(for example,Internet phone).Host A converts analog voice to a digital 64Kbps bit stream on the fly. Host A then groups the bits into 48 bytes packets. There is one link between host A and B:its transmission rate is 1 Mbps and its propagation delay is 2 msec. As soon as host A gathers a packet, it sends it to host B. As soon as host B receives an entire packet, it converts the packet's bits to an analog signal. How much time elapses from the time a bit is created ( from the original analog signal at host A)until the bit is decoded(as part of the analog signal at hostB)？ ======================================================================= 2. suppose two hosts , A and B, are separated by 10,000 kilometers and are connected by a direct link of R = 1Mbps . Suppose the propagation speed over the link is 2.5 x 10^8 meters/sec. (a) Calculate the " bandwidth - delay product", R‧t prop (b) Consider sending a file of 400,000 bits from host A to host B. Suppose the file is sent continuously as one big message. What is the maximum number of bits that will be in the link at any given time. (c)Provide an interpretation of the bandwidth-delay product. (d)What is the width (in meters) of a bit in the link ?Is it longer than a football field? (e)Derive a general expression for the width of a bit in terms of the propagation speed s, the bandwidth R, and the length of the link m. ======================================================================= --

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