To support intersite connectivity, enterprises are in the midst of migrating from legacy services like private line, Frame Relay (FR), or asynchronous transfer mode (ATM) to IP (Internet protocol)-based services. Based on key requirements like performance, security, availability, and accessibility, organizations tend to standardize around one WAN topology and interconnect to others as required. For example, organizations with extremely distributed intranetworking requirements often use public multiprotocol label switching (MPLS), IP VPNs, or a hybrid MPLS-IP VPN service infrastructure, whereas firms with fewer and larger locations and higher performance or security requirements tend to favor private MPLS or Ethernet services.