MPCs leverage the Junos Trio chipset to deliver the industry's highest Ethernet densities, as well as the flexibility of modular interface cards (ATM/Sonet/Ethernet) across the MX Series portfolio. These advanced capabilities allow customers to flexibly mix and match interfaces to create service-specific and "pay as you grow" configurations. The MPC houses the PFEs to deliver comprehensive Layer 3 routing (iPv4 and iPv6), MPLS, and Layer 2 switching. These MPCs also support inline services and advanced hierarchical quality of service (HQoS) per MX Series slot.