On Thu, May 10, 2012 at 3:02 AM, David Woodhouse <[email protected]> wrote: > > If we overload the DSLAM, it drops one ATM cell out of N, which nixes > fairly much *every* IP packet by dropping a tiny part of each one, and > results in almost zero throughput. We don't let the DSLAM do > buffering :)
<tangent> Can't they turn on Early Packet Discard or something similar? This seems like a no-brainer. Dynamics of TCP Traffic over ATM Networks (1994), Allyn Romanow , Sally Floyd http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.30.7647 "We investigate the performance of TCP connections over ATM networks without ATM-level congestion control, and compare it to the performance of TCP over packet-based networks. For simulations of congested networks, the effective throughput of TCP over ATM can be quite low when cells are dropped at the congested ATM switch. The low throughput is due to wasted bandwidth as the congested link transmits cells from `corrupted' packets, i.e., packets in which at least one cell is dropped by the switch. We investigate two packet discard strategies which alleviate the effects of fragmentation. Partial Packet Discard, in which remaining cells are discarded after one cell has been dropped from a packet, somewhat improves throughput. We introduce Early Packet Discard, a strategy in which the switch drops whole packets prior to buffer overflow. This mechanism prevents fragmentation and restores throughput to maximal levels." </tangent> _______________________________________________ Bloat mailing list [email protected] https://lists.bufferbloat.net/listinfo/bloat
