On Mon, 16 Mar 2009, Leo Bicknell wrote:
What appears to happen is vendors don't auto-size queues. Something
In my mind, the problem is that they tend to use FIFO, not that the queues are too large. This is most likely due to the enormous price competition in the market, where you might lose a DSL CPE deal because you charged $1 per unit more than the competition. What we need is ~100ms of buffer and fair-queue or equivalent, at both ends of the end-user link (unless it's 100 meg or more, where 5ms buffers and FIFO tail-drop seems to work just fine), because 1 meg uplink (ADSL) and 200ms buffer is just bad for the customer experience, and if they can't figure out how to do fair-queue properly, they might as well just to WRED 30 ms 50 ms (100% drop probability at 50ms) or even taildrop at 50ms. It's very rare today that an end user is helped by anything buffering their packet more than 50ms. I've done some testing with fairly fast links with big buffers (T3/OC3 and real routers) and doing FIFO and tuned TCP windows (single session) it's easy to get 100ms buffering, which is just pointless. So either smaller buffers and FIFO, or large buffers and some kind of intelligent queue handling. -- Mikael Abrahamsson email: swmike@swm.pp.se