Emulating ADSL bandwidth shaping

Aria Stewart aredridel at nbtsc.org
Tue May 4 04:15:32 UTC 2010

On May 3, 2010, at 9:19 PM, Patrick Giagnocavo wrote:
>> - 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).

And queues of 1 second at line rate are not uncommon, so if you load the link, things lag. 

> 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.

Now more typically 40ms. And yeah, no bursts over normal line rate. Most turn down line rate for other plans, not shape.

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