Rohit
http://www.herring.com/mag/issue33/atm.html
[An Excerpted Interview with former employee #1 of Sun]------------------------
THE HERRING: What are some of the major problems with ATM?
Bechtolscheim: The biggest problem is that ATM is connection-oriented: you
need to establish an end-to-end connection before you can send any data. Well,
IP is a dynamic link state protocol, which uses routers to forward packets.
There is no notion of an end-to-end connection set-up.
On the Internet, half the traffic now is Web-related. Every time you click on
one of these links, you open up a connection to another server. The average
http data transfer is about two kilobytes. At 155 megabits per second, it
takes 100 microseconds to transfer two kilobytes. With Fore's market-leading
ASX 1000 switch, the connection set-up time is ten milliseconds. So the
connection set-up time is 99% of your throughput, meaning throughput isn't 155
but 1.5 megabits, which is no better than a T1 line. This whole notion of
connection set-up is just fundamentally incompatible with increasingly dynamic
IP environments.
ATM was supposed to be great for multimedia, but it turns out, it's basically
incompatible with IP Multicast, which is the underlying technology that
people use to deliver multimedia; there is no mapping of IP Multicast to ATM
short of building a replication server that sends out little packets for each
subscriber, which is not multicast but replication. If you look at the people
trying to do video applications to the desktop like Judy Estrin's
company--Precept--they are making multimedia work over Ethernet because there
is no market for video to the desktop over ATM. Application developers have to
use what's out there, which is Ethernet. And video works just fine over
Ethernet. It's no big deal. It's just people didn't think about it before, so
nobody worked on it.
On the business side, ATM and Ethernet have completely different economic
models. Ethernet is an open, competitive , multi-vendor environment: you can
plug things in; they're cheap; and people understand how they work. ATM is
basically a vertically integrated proprietary network model: if you buy one
ATM switch from one vendor, it's not going to work with a switch from the next
guy. And there is no network management.
Bottomline, the fact is that ATM never worked as advertised. We have not
found one production installation that has deployed ATM in the way it was
intended. People have done all kinds of prototype experiments. Everybody had
to buy a switch, but in the end,the promise didn't get filled. The technology
did not deliver.