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Lack of scalability hampers efficiency, raising costs When ATM was first unveiled many people pointed to link inefficiency as a glaring issue. Supporters of ATM re¬butted this argument by pointing out the operational efficiencies achievable by the consolidation of all services into one platform. Unfortunately, as networks grew with ATM deploy¬ments, this claim did not hold water. ATM switches and lP routers were overwhelmed by the large volume of PVCs generated by DSLAMs & lADs.

The scalability problem ATM technology created caused the need for platforms to optimize, aggregate and concentrate edge network traffic. Hence ATM edge switches, edge routers, concentration routers, and PVC aggregation platforms came into service. This proliferation of platforms designed to deal with ATM's scalability issues quickly eroded the profits of those who deployed it. The approach of using ATM throughout the network, including the edge, forced the superimposition of an additional layer of encapsulation, usually in the form of PPP tunneling, to more effectively move traffic around. This encapsulation process added to traffic overhead and further reduced link efficiency.



With the addition of aggregation platforms, the need for management systems to control and configure these solutions followed. The impact on the service provider goes beyond the cost of adding and maintaining the additional management system. The greatest expense is in the integration of the management platform with existing ass systems. This became easier as vendors incorporated the management system of aggregation equipment into their existing management platforms by creating multi-module management system. However, this also created a huge disincentive to acquire "best of breed" equipment from different ven¬dors, forcing a reduction in choice for the operators.

ATM has proven to be cost prohibitive for smaller markets to deploy for numerous reasons. Even today, with lower DSLAM costs, the capital required to deploy ATM in many medium-sized markets far outweighs the return. To deploy an ATM-based DSLAM solution, the service provider needs to acquire an ATM PVC aggrega¬tion platform and edge routing equipment needed to convert from Asynchronous transfer mode WAN interfaces to typical Ethernet-based LAN interfaces, requirements that significantly add to the cost-per-port equation when a small number of ports are involved. This likewise translates into additional costs in the form of more employee training, multiple management platforms, multiple service and support contracts, numerous spares, and elevated network engineering efforts required to address multi-layer redundancy issues. The resulting costs outstrip the benefits of providing the service.