Service providers are searching for ways to expand the capacity of their networks to meet the growing demand for IP–based services. The primary alternatives for IP transport include IP over PPP over SONET/SDH networks (sometimes referred to as PoS), and IP over ATM over SONET/SDH (IP over ATM).

PoS is a high-speed method of transporting IP traffic between two points. IP over ATM offers a feature-rich environment for the provision of value-added IP–based services such as IP–based virtual private networks (VPNs), including definable classes of service (CoS) and support for deterministic service-level agreements (SLAs).

Service providers that wish to sell IP–backbone services to customers with similar service needs (that is, those in the public arena that do not want to offer service guarantees) may benefit from using PoS. Those that wish to sell differentiated services to gain a competitive edge in an overcrowded IP–transport market will want to consider the superior bandwidth management and quality of service (QoS) guarantees available using IP over ATM.

In the majority of cases, each service provider will use a mix of these technologies to provide the best solution for the variety of markets that are part of its service base.