Re: cable guy "vapor"-izes DSL 3X cable TV troll!

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#488

From: Randy S.
Date: Fri, 02 Feb 2001 22:32

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> >We're getting closer to the key metric to compare cable with DSL:
> >   *Upstream oversubscription rate*
>
> I don't think so.  Upstream oversubscription is really an issue only on
> cable, since (1) DSL has dedicated upstream to the DSLAM, and (2)
> backhaul links are symmetric (as compared to asymmetric subscriber
> connections).

Hmm, I think I see what you're saying.  Since the head end of a DSL link is
symmetrical, and only the individual links are asymmetrical, the upstream
backbone links will nearly always be considerably more lightly loaded than the
downstream links.  So the only way a DSL line will be subject to an overloaded
upstream channel is if the provider uses too high an asymmetry ratio (I think
we calculated that the effect would be seen starting at around a 10:1 ratio,
and be very serious at around 15:1).  Conversely, since cable aggregates the
channels along each segment, it can overload the upstream channel even IF each
individual asymmetry ratio is not too high.

Randy S.

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Subject: Re: cable guy "vapor"-izes DSL 3X cable TV troll!
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