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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Internet speed report...
Michael Dillon writes: > In the paper > http://klamath.stanford.edu/~keslassy/download/tr04_hpng_060800_sizing.pdf That's also in the (shorter) SIGCOMM'04 version of the paper. > they state as follows: > ----------------- > While we have evidence that buffers > can be made smaller, we haven't tested the hypothesis > in a real operational network. It is a little difficult > to persuade the operator of a functioning, profitable network > to take the risk and remove 99% of their buffers. But that > has to be the next step, and we see the results presented in > this paper as a first step towards persuading an operator to > try it. > ---------------- > So, has anyone actually tried their buffer sizing rules? > Or do your current buffer sizing rules actually match, > more or less, the sizes that they recommend? The latter, more or less. Our backbone consists of 1 Gbps and 10 Gbps links, and because our platform is a glorified campus L3 switch (Cisco Catalyst 6500/7600 OSR, mostly with "LAN" linecards), we have nowhere near the buffer space that was traditionally recommended for such networks. (We use the low-cost/performance 4-port variant of the 10GE linecards.) The decision for these types of interfaces (as opposed to going the Juniper or GSR route) was mostly driven by price, and by the observation that we don't want to strive for >95% circuit utilization. We tend to upgrade links at relatively low average utilization - router interfaces are cheap (even 10 GE), and on the optical transport side (DWDM/CWDM) these upgrades are also affordable. What I'd be interested in: In a lightly-used network with high-capacity links, many (1000s of) active TCP flows, and small buffers, how well can we still support the occasional huge-throughput TCP (Internet2 land-speed record :-)? Or conversely: is there a TCP variant/alternative that can fill 10Gb/s paths (with maybe 10-30% of background load from those thousands of TCP flows) without requiring huge buffers in the backbone? Rather than over-dimensioning the backbone for two or three users (the "Petabyte crowd"), I'd prefer making them happy with a special TCP. -- Simon.
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