ATM Utility

Pushpendra Mohta pushp at CERF.NET
Wed Nov 9 07:28:11 UTC 1994

Curtis Villamizar writes:
> In message <9411080848.AA16753 at>, Tim Salo writes:
> > 
> > Most ATM pricing I have seen has a "committed information rate"
> > component, which assures a minimum available bandwidth.  This is not
> > the "metered" pricing to which you are responding.
> > 
> > -tjs
> Tim,
> None of us has tried to hook up a small business or our PeeCee at home
> to an ATM netwpork and see if setting up and SVC to ftp.*.* at some
> low rate is proportional to the cost of asking for a PVC at 10s of
> Mb/s, for obvious reasons (no one offers it - in case anyone can't see
> the obvious reasons).  It might end up being orders of magnitude
> cheaper to get some other type of connection to an IP provider below
> some bandwidth threshhold than an ATM connection and paying per SVC.
> For example, it is quite easy to exceed $1,000/mo using IP over POTs
> or IP over ISDN with usage sensitive billing (within the same city),
> while a leased circuit would be far cheaper.  I have existance proof
> of that (both involve home use).
> Curtis

There is a distinction to be made here between 1. IP vs ATM  and
2. IP over ATM.  I think you are talking about 1, and I agree. But 
Vadim and Tim were talking about 2.

Yes, PPP over SONET will give you better utilization of the link,
but building a 3-4 node mesh network is going to be cheaper with fast
packet services ( ATM/SMDS/Frame Relay ) than with point to point
links. We have implemented quite a few of these meshes.

The only place point to point links will be more cost effective
are when you absolutely need the entire bandwidth of each point
to point link.

As to metered vs unmetered service, it will always be cheaper
to go unmetered beyond a certain threshold of usage. Some
fast packet service vendors I know of cap their metered usage within a
few % ( ~20 ) of what they would charged if you would have opted for
flat rate unmetered service. At the IP service level, some
ISPs ( CERFnet, for example ) will offer both a metered and
flat rate version of the same switched access service.


Pushpendra Mohta              pushp at        +1 619 455 3908
Director of Engineering                             +1 800 876 2373

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