Cell Relay Archive

[Jon.Harley@warwick.ac.uk (Jon Harley)]

"Chan Kok Kee" <ckokkee@singnet.com.sg> writes:
>As far as I know there is no public service provider in the world that is
>selling ABR service.

I understand several of the major carriers in the USA do so.

> It is difficult to implement, provision, manage and
>most important bill.

It's easier to implement/provision/manage than UBR in that the network
no longer has to guarantee a particular cell delay variation (CDV). I
don't know how it's typically billed, perhaps flat rate.

> What REAL purpose does it serve when there is VBR-NRT
>and UBR?

The very real purpose it servers is allowing providers to sell bandwidth
twice. The first time they sell a fixed amount to someone wanting VBR,
say. Then in all the times when that traffic isn't at its peak rate,
they can squeeze some ABR traffic through any parts of the network
which aren't busy, and charge the user for doing so - selling the
same bandwidth twice. Because CDV doesn't have to be guaranteed it
can be allowed to hang around in the less busy parts of the network
if neccessary. The other advantage is that it's extra-efficient because
cell loss is guaranteed to be low, unlike UBR.


Jon

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