Customer oversubscription levels

Arman arman at unitedlayer.com
Tue May 28 21:35:39 UTC 2002


Typically Class 4 have an over subscription ratio of 4:1, the biggest Class
4 switches can handle 40,000 DS0s like the AT&T 5Ess or DMS 500 switches.

A over subscription ratio of 100000/5000= 20 is too high for PSTN.

FYI modem to user ratios are 10:1 on the average.
ak


"Stephen J. Wilcox" wrote:
> 
> I'd look at this slightly differently.. customers wont use all their
> available bandwidth at once anyway so you will get aggregation simply by
> economy of scale.
> 
> Compare to say the PSTN, there might be say 100000 local customer lines
> attached to a particular exchange and yet the capacity out onto the trunk
> network might be say 5000 lines. Clearly there is a high degree of over
> subscription and phone customers are the first to complain when they cant
> dial out and yet it doesnt happen because not everyone uses it at once.
> 
> The same is true for bandwidth, you can achieve a good level of
> aggregation - say 5:1 and yet each customer can max out their own link
> because they dont all do it at once
> 
> The problem comes when you either just dont have trunk capacity or you try
> to put far too many customers onto a node.
> 
> I always call it aggregation vs contention - in one you achieve economy of
> scale and in the other you knowingly degrade service (within the bounds of
> an SLA)
> 
> So, to answer your question, it depends what your selling as to how much
> oversubscription you can achieve, anything for 3:1 to 20:1 depends on if
> its transit, leased line, broadband, dialup... but I think you should look
> more at whether you are actually degrading an individuals service or just
> achieving aggregation.
> 
> Steve
> 
> On Tue, 28 May 2002, Mathew Lodge wrote:
> 
> >
> > This might be a dumb question, but I can be sure that I'll be told if
> > that's the case, so here goes:
> >
> > What's a good oversubscription ratio for customer traffic to global
> > Internet bandwidth these days? I.e., if you have, say 90megs of bandwidth
> > to other transit providers, how much bandwidth, in aggregate, are you
> > selling to customers -- 90? 450? 900?
> >
> > Do customers care about this? Or do they assume that if they get a T1 to
> > the Internet from you that they have their own T1's worth of non
> > over-subscribed bandwidth to your transit providers?
> >
> > Thanks,
> >
> > Mathew
> >
> >



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