Emulating ADSL bandwidth shaping

Scott Weeks surfer at mauigateway.com
Tue May 4 12:14:24 CDT 2010


--- cboyd at gizmopartners.com wrote:
From: Chris Boyd <cboyd at gizmopartners.com>
On May 4, 2010, at 7:27 AM, Marshall Eubanks wrote:

> I am not sure what the point is in mixing in speed of light 
> latency. If your "typical sites" are, say, Indian cricket 
> blogs, you will typically have a high latency from the US. 
> What does that tell you about your DSL or Cable system, 
> except that it is somewhat removed from India ?

: Most of the ADSL installations I've seen in SBC 13 state area 
: had interleaving turned on, which significantly increases latency.
: I suspect that's why many cable MSOs in the same territory have 
: "cable is better for gaming" marketing campaigns running all the time.
:
: So the latency you see on an ADSL line is dependent on how the 
: carrier set up the DSLAM.


In the system I work on, which is in a state with many rural areas and an OSP that goes through a lot of very wet and very windy areas, has "Interleaved" turned on to correct errors.  This adds ~25msec between the CPE and the nearest router.  Sometimes folks ask for it to be changed to "Fast".  We explain that errors may cause resyncs to happen and then make the change if the customer still wants it.  That takes the latency from ~25msec to ~3-4msec.  So use both when doing your modeling.  I don't know how to model the error rate, though, as that would be dependent on the quality of the OSP you're modeling...

scott


ps. if you're so fast in gaming that a difference of 1/5 of a second makes a difference you're good...  ;-)




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