Legacy Copper Access Networks based on Plesiochronous Digital Hierarchy (PDH) and Optical Metro Networks based on Synchronous Optical Network (SONET) or Synchronous Digital Hierarchy (SDH) technologies set the standards for reliability capacity and efficiency transporting time-division multiplexing (TDM) traffic and carrying voice and data services. Service Providers and Carriers are nonetheless faced with many challenges and limitations imposed by these legacy networks and need alternatives for migrating their circuit-switched transport networks to future-proof packet-based network.

The Cisco® ASR 900 Series address the legacy network inefficiencies by delivering a cost-effective modular solution based on a protocol-independent fabric architecture. The Cisco ASR 900 Series as part of the Cisco Evolved Programmable Network (EPN) architecture is capable of delivering unbounded scale and unmatched Circuit Emulation (CEM) and Optical Transport Network (OTN) capabilities in addition to Carrier Ethernet business services over a redundant and protected packet-based network (Multiprotocol Label Switching [MPLS]/FlexLSP).