title: A future that never was

A future that never was

By Scott Bradner

Many people seem to consider me an ATM opponent. I consider myself an ATM realist. Wearing whichever hat you place on me I'd like to engage in a bit of an ATM post mortem.

Once upon a time the future was to be 'all-ATM, all the time.' For years I saw projections of X billion dollars worth of ATM sales N years in the future. X and N varied depending on the consulting firm that was putting out the projection but the values of X and N seemed to stay consistent year after year from any individual consulting firm. In absolute terms ATM has grown into a reasonable sized business but it remains a very small part of the overall networking market.

It is a bit of a cheap shot to talk about the fate of desktop ATM so I'll let dead dogs lie and move on to two places where ATM was expected to take over the market: backbone and access networks.

With all the speed that they can muster telephone companies have been rolling out ATM-based service at a glacial pace. Many places in the country you can get ATM VC-based connections, some even have distance-insensitive pricing making them very attractive indeed. Many companies are signing up for these services but I think this will be a short-lived phenomena. I expect that IP-based services, including IP-based VPNs will take over this market. In addition I don't see much future for ATM in supporting IP backbone services. ATM is good at splitting up links into smaller pipes but this does not seem to be all that useful a function when ISPs are growing to the point where they need full OC48 and OC192 links between POP locations. I expect that MPLS will be used instead of ATM in the places where links still need to be subdivided.

That leaves access networks. This may come as a surprise to some of my regular readers but I think ATM functionality is a good match for the requirements of access networks. Links to individual locations tend to be small and if there is a desire to multiplex multiple services over that link ATM seems to me to be a better technology than IP. For example I expect to see a lot of ATM-supported integrated access devices (IADs) being deployed as part of telco-based DSL services. This is partly because much of the telco world hungers for any way to maintain the circuit-based philosophy of the telco networks. ATM will not give them much satisfaction in this case because the ATM VC will only span the access link and not be end-to-end.

ATM proponents irrationally assumed that a single technology would meet all networking requirements and a lot of money was lost to that assumption. I wonder if some IP proponents are guilty of the same hubris.

disclaimer: Harvard and hubris in the same article? No way, so the above must be my own opinion.