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UNCLASSIFIED Future Issues in Router Security Version 1.0g  UNCLASSIFIED 207   7.2.  ATM and IP Routing Asynchronous transfer mode (ATM) switched networks are popular for backbones and long-haul high-speed network links.  ATM is a very big topic, most of which is out of the scope of this guide.  Sometimes, the boundary between switched ATM and routed IP will be a switch or router with one or more ATM interfaces and one or more traditional LAN or WAN interfaces (e.g. Ethernet, Frame Relay). Cisco routers support three mechanisms for sending IP traffic over ATM switched networks. 1.     Classical IP –   This is the oldest technique, and offers very simple configuration at the cost of flexibility and performance.   2.     LANE –   LAN Emulation (LANE) is a fairly general, standardized technique for extending an IP LAN over an ATM switched network.  It offers a great deal of flexibility, but requires a great deal of configuration to deploy. 3.     MPOA –   Multi-Protocol Over ATM (MPOA) is a highly flexible set of mechanisms for transporting IP and other protocols over ATM switched networks.  Used with LANE, MPOA allows routers and other network devices to take advantages of advanced ATM facilities (like ATM quality-of-service). The security implications of choosing one of these modes over another are not yet entirely clear.