The rapid growth of Internet-enabled user applications has led to a dramatic growth in the bandwidth provisioned through service provider networks. To accommodate this growth, service providers are consolidating their various existing network architectures that deliver traditional Layer 2 WAN transport, such as Frame Relay and ATM, with architectures that deliver Layer 3 WAN services, such as high-speed Internet access and Layer 3 virtual private networks (VPNs). This consolidation optimizes service providers' capital investments so that all such expenditures simultaneously benefit all network services.Achieving network consolidation is particularly challenging at network aggregation points. The devices at these network aggregation points must be able to deliver a wide variety of Layer 2 and Layer 3 services, while providing efficient transfer of network traffic from customer access nodes to the core network and back. Therefore, these aggregation devices must simultaneously provide scalable bandwidth and interface density between the access and core networks; support a wide range of network protocols, as well as quality-of-service (QoS), security, and accounting features; and be compatible with existing SONET infrastructure.The Cisco 7600 Series Routers meet these requirements because it provides the performance, density, and features that are needed for network aggregation devices in consolidated network architectures.To provide aggregation services over an existing SONET infrastructure, the Cisco 7600 can be configured to support various SONET interface cards, such as OC-3c STM-3 Packet-over-SONET (POS) Optical Services Modules (OSMs). These interface cards include both the original OSMs and the new enhanced OSMs, which deliver advanced IP and Multiprotocol Label Switching (MPLS) services based on the Cisco Parallel Express Forwarding (PXF) network processor.