Customer oversubscription levels

Tue May 28 22:45:32 UTC 2002

Yeah sorry should have included a disclaimer! My numbers for PSTN were
made up as I dont have any real figures to hand or in my head .. it was
more the analogy I wanted to demonstrate as people seem to understand
aggregation in local exchanges better than bandwidth contention even tho
its the same really..

Ok real life.. How about we have about 200 extensions on our PBX but only
30 lines onto the provider network and yet we never see engaged...

Steve

On Tue, 28 May 2002, Arman wrote:

> 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
> > >
> > >
> 