"Clock rate 64000" 与我们平常所说的带宽有无关系?
这个问题思科有解答：
Be aware that the fastest speeds might not work if your cable is too long, and that speeds faster than 148,000 bits per second are too fast for EIA/TIA-232 signaling. It is recommended that you only use the synchronous serial EIA/TIA-232 signal at speeds up to 64,000 bits per second. To permit a faster speed, use EIA/TIA-449 or V.35.
线缆过长，时钟速率过快，都会导致可能的丢包。
思科建议64000这个值在EIA/TIA-232信号类型的线上做设置，而更高的clock rate需要其它类型的线缆，表明clock rate与实际物理速率是有关系的，速率设置超过实际物理线缆所能承受的话，可能会发生丢包等问题。
下面还有一些简短资料可供参考：
Desired clock rate in bits per second: 1200, 2400, 4800, 9600, 19200, 38400, 56000, 64000, 72000, 125000, 148000, 250000, 500000, 800000, 1000000, 1300000, 2000000, 4000000, or 8000000.
For the synchronous serial port adapters (PA-8T-V35, PA-8T-X21, PA-8T-232, and PA-4T+), a nonstandard clock rate can be used. You can enter any value from 300 to 8000000 bps. The clock rate you enter is rounded (adjusted), if necessary, to the nearest value your hardware can support except for the following standard rates: 1200, 2400, 4800, 9600, 14400, 19200, 28800, 38400, 56000, 64000, 128000, or 2015232.