METRODATA LTD
WCM1100 / WCM3100 / WCM-Serial
User Manual
76-02-082 Rev J
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5.2.5 Rate Limiting Mode
Each port supports rate limiting to police the input traffic stream. This configuration items
determines the method of calculating the traffic stream bandwidth. The options are as
follows:
Utilisation
User frame, (DA to FCS) + Pr IPG
Information Rate
User frame, (DA to FCS)
L3 Rate
User frame, (DA to FCS)
– 18 ( - 4 if tagged )
For Ethernet to operate correctly, each frame is transmitted with an 8 byte preamble to
allow for clock synchronisation, and a minimum interpacket gap (IPG) of 12 bytes.
Thus, for a wirespeed packet stream of 1488095, 64 byte packets per second, the three
different bandwidths calculate as follow:
Utilisation
( 64 + 8 + 12 ) * 8 * 1488095 = 999,999,840bps
Information Rate
64 * 8 * 1488095 = 761,904,640bps
L3 Rate
( 64
– 18 ) * 8 * 1488095 = 547,618,960bps
