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RFC 2544: Ethernet allows for a plus or minus (+/-) .01% deviation for...

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Comment by cstuartj
Submitted on 2/1/2005
Related RFC: RFC 2544
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Ethernet allows for a plus or minus (+/-) .01% deviation for the nominal clock rate. This means that not all Ethernet devices can transmit the same maximum amount of frames per second. According to the Ethernet Specification (802.3), the nominal frame rate for 64 Byte frames at Gigabit Ethernet speeds should be 1,488,095 frames per second. But because of the +/- .01% clocking variation that a Ethernet device can have from the nominal speed the actual frame rate can be +/- 148.8 frames per second. This yields a range of maximums from 1,487,946 to 1,488,244 frames per second, or a .02% difference in total frames per second. In the real world this can translate to frame loss between Ethernet devices that have different maximum rate abilities. This frame loss does not necessarily mean test failure, but may just indicate a clock tolerance difference between the ports. It is important to account for this difference in the test setup and pass/fail criteria.-Stuart JohnsonWorld Wide Packets

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