How Washington Mutual divided its Multi-protocol Label Switching network into six layers.Back to WaMu banks on MPLS1. Metropolitan-area network: Each of WaMu's 3,000 locations feed\u00a0LAN\u00a0traffic into one of multiple\u00a0MANs. Connectivity from MAN to MAN is achieved using\u00a0dense wave division multiplexing\u00a0and\u00a0SONET\u00a0ring technologies.2. Supercore: A supercore provides a gateway for handoff of MAN traffic into the wide-area\u00a0MPLS\u00a0network. Supercores connect to the\u00a0MCI\u00a0network for primary service via two SONET OC-3 (155M bit\/sec) trunks and to back-up carrier\u00a0AT&T\u00a0over a single OC-3 circuit. With each of these consolidated nodes, WaMu can partition the MPLS\/WAN backbone to make upgrades, to contain security breaches, and to activate new sites without affecting overall performance of MPLS and desktop traffic.3. MPLS\/WAN backbone: MCI-based MPLS network handles supercore-aggregated traffic and consists of nine nodes that collapse into a three-node backbone.4. Access layer for business partners. WaMu provides MPLS partners AT&T,\u00a0Cisco,\u00a0Juniper\u00a0and MCI access to back-office systems running administrative, billing and management applications. This layer is firewall-protected.5. Disaster-recovery layer. Details largely undisclosed, but this layer provides excess capacity, backup and storage in the event of network failure.6. Dial back-up layer\/ISDN: Provides a connectivity option should the MPLS network or MCI's infrastructure as a whole go down.