The Cisco 10005 edge services router (ESR) is a high capacity Layer 3 router optimized to support selected Cisco IOS software services at wire speed performance on thousands of DS1/T1 connections. Designed primarily for use in a central office environment, it provides interfaces that connect to large numbers of subscribers using low-speed circuits, and then funnels all subscriber traffic into a small number of high-speed trunk interfaces. The chassis contains five line card slots and two slots for Performance Routing Engine (PRE) modules.