In the real world, the hardware buffer size is rarely matched to the real BDP. There are several reasons for this, but a couple of fundamental ones are:
- BDP varies with RTT, which is in general different for flows simultaneously using the same link/queue to reach different remote hosts, and therefore cannot be accurately predicted by a hardware vendor. - Frequently, the queue size is tuned for the maximum capability of the device and a pessimistic value for RTT, but the same hardware is more often used (at least initially) at lower link speeds and thebqueue size is not adjusted to compensate. Eg. DOCSIS 2 cable but DOCSIS 3 modem, Ethernet NIC or switch capable of 1000Mbps but operating at 100 or even 10, 802.11ac wifi struggling with a marginal 802.11g link... Thus substantially oversized raw buffers are quite normal. It is AQM's job to keep the *actual* queue occupancy low; with a properly functioning AQM, the effects of an oversized raw queue are nil. - Jonathan Morton
_______________________________________________ aqm mailing list [email protected] https://www.ietf.org/mailman/listinfo/aqm
