> On 9 Jun, 2015, at 19:11, Steven Blake <[email protected]> wrote: > > On a 10 GE link > serving 2.5 MPPs on average, CoDel would only drop 0.013% of packets > after 1000 drops (which would occur after 6.18 secs). This doesn't seem > to be very effective.
Question: have you worked out what drop rate is required to achieve control of a TCP at that speed? There are well-known formulae for standard TCPs, particularly Reno. You might be surprised by the result. Fundamentally, Codel operates on the principle that one mark/drop per RTT per flow is sufficient to control a TCP, or a flow which behaves like a TCP; *not* a particular percentage of packets. This is because TCPs are generally required to perform multiplicative decrease upon a *single* congestion event. The increasing count over time is meant to adapt to higher flow counts and lower RTTs. Other types of flows tend to be sparse and unresponsive in general, and must be controlled using some harder mechanism if necessary. One such mechanism is to combine Codel with an FQ system, which is exactly what fq_codel in Linux does. Fq_codel has been tested successfully at 10Gbps. Codel then operates separately for each flow, and unresponsive flows are isolated. - Jonathan Morton _______________________________________________ aqm mailing list [email protected] https://www.ietf.org/mailman/listinfo/aqm
