Srikanth Sundaresan wrote:
I'm trying to model ADSL access link bandwidth shaping. With a link of 18Mbps, I'm using a token bucket filter (tc + netem) to model 10Mbps, 8Mbps and 2Mbps access plans. I have a couple of questions:
- do ISPs typically use token bucket filters with large bursts to shape traffic? - what kind of burst sizes and latencies/limits are typically used for the filter?
You will definitely have to account for latency. For emulating cable traffic, latencies (in the USA) will be about 60-80ms to typical sites. Burst mode in my experience occurs only for about the first 15 seconds, then is throttled back (though not always; seems to depend on time of day). For DSL, I seem to recall latency being about 90-110ms (note, I haven't used DSL in many years). Burst mode was generally not noticeable or available, that is, you got the same speed regardless of downloading a 1MB jpeg or a 640MB .iso file. IMHO, IME, ISTR, YMMV... --Patrick