🚀 go-pugleaf

> Even though bandwidth between the DSLAM and aggregation router is
> assymetric (e.g. 45Mbps full-duplex), you could still saturate upstream
> before downstream, depending on what users are doing.

I assume you meant SYMMETRIC here?  ;-)

> For example, if 5% (175) of the ~4000 ADSL users aggregated into a DS3
> ran active web servers (uploading at constant 256Kbps), you'd saturate
> the upstream.  I'm not saying that this is extremely likely, but I
> believe the best way to quantify the probablility is to quantify:
> upstream oversubscription rate

I think I was describing essentially the same thing before (at least that's
what I was TRYING to say).  But as you say, I don't think this would be very
likely on DSL.  I think John is saying that this is MUCH more likely to happen
on Cable due to the shared ASYMMETRICAL upstream channel.  At least by the time
the DSL upstream channel is shared, it's symmetrical.

> In fact we already know that the way to compare different ISPs to each
> other is to understand their downstream oversubscription policies.  What
> I find intriguing, is that you need to look at upstream as well...this
> is a real eye-opener for me.

Yes, this is the fallout of our MUCH earlier TCP asymmetry discussion (which
predated this thread).  The consequences of this are STILL raising new issues,
such as the one John pointed out.  I don't think the Internet tech community
had much considered the effect of asymmetry on Internet traffic before just
recently.

> I suspect that few considered the impacts of upstream saturation on ADSL
> throughput...or ADSL downstream traffic saturating the reverse channel
> of their T1 customers...hmmmmm.

I wonder if any Network engineers responsible for backbone maintenance are
reading this.  I bet their blood pressure just went up! ;-)

Randy S.