作者freepark (自由‧公园)
看板Network
标题Re: [问题] 如何计算frame size?
时间Sun Mar 27 02:30:58 2005
※ 引述《kheng (呆呆)》之铭言：
: 1.
: Consider a CSMA/CD network running at 1 Gbps over a 1-km calbe with no
: repeaters. The signal speed in the cable is 200,000km/sec. What is the
: minimum frame size?(note:1Gbps=1,000,000,000 bits/sec)
(1/200,000) * 2 * 1,000,000,000 / 8 = 1250 bytes
: 2.
: A TCP machine is sending windows of 65535 bytes over a 1-Gbps channel that
: has a 10-msec one-way delay.What is the maximum throughput achievable?
: what is the line efficiency?
(65535 * 8) / (0.01 * 2) = 26,214,000 bps
26,214,000 / 1,000,000,000 = 2.6%
: 3.
: If message, 01110011001, is send and a special bit pattern,01110, is applied
: as the leading flag of the message. The generator ploynomial G(x)=x^4+x^2+x+1,
: is used for CRC examination.
: 1.Is the CRC check used for error detection or error correction?
: 2.Find the checksum?
: 3.If the frame shall be transmitted as
: ---------------------------------------------
: |Leading Flag |Message body | CRC checksum |
: ---------------------------------------------
: Construct the bit pattern the frame to be transmitted(hint:bit stuffing)
error detection
0001
01110 0110100110001 0001
not very sure...
: 4.
: The mzsimum payload of a TCP segment is 65495 bytes. Why was such a
: strange number chosen?
65535 - 20 - 20 = 65495
: 请顺道寄去我信箱...谢谢
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※ 编辑: freepark 来自: 203.67.96.93 (03/27 15:12)