Historically, many enterprises leased SDH/SONET connectivity from service providers for their TDM traffic. However, IP/Ethernet is now ubiquitous for services and applications, with MPLS as the WAN transport technology. With the dramatic cost, footprint and power reduction offered by MPLS over SDH/SONET, if enterprises migrate their TDM services to run on these MPLS networks they can dramatically reduce their leased connectivity costs.
Circuit emulation provides the mechanism to achieve this, with direct E1/DS1, DS3, and STM-1/4, OC-3/12 interfaces allowing existing services to be connected directly to the packet network. The packet network is able to provide a variety of resilience options, allowing it to achieve the same level or better service resilience than was provided by the legacy SDH/SONET network:
- G.8032v1: Recommended for access protection
- MC-LAG (Multi-Chassis Link Aggregation Group): Allows the traffic to be shared over multiple chassis, as well as providing redundancy in the event one of the chassis fail
- LDP (Label Distribution Protocol): Used to provide end to end protection
Moving to a packet network has the added advantage of simplifying enterprise access. Running the SDH/SONET services on the packet network gives operators the opportunity to consolidate all enterprise services onto a single CPE, simplifying the expenses and complexity associated with running two networks. In addition, transitioning services from SDH/SONET to IP becomes far simpler for the Enterprise