in 1984. Lack of interoperability and standardization prevented any significant Frame Relay deployment until 1990, when Cisco, Digital Equipment Corporation (DEC), Northern Telecom, and StrataCom formed a consortium to focus on its development. They produced a protocol that provided additional capabilities for complex inter-networking environments. These Frame Relay extensions are referred to as the local management interface (LMI). Datalink connection identifiers (DLCIs) are numbers that refer to paths through the Frame Relay network. They are only locally significant, which means that when device-A sends data to device-B it will most likely use a different DLCI than device-B would use to reply. Multiple virtual circuits can be active on the same physical end-points (performed by using subinterfaces). The LMI global addressing extension gives Frame Relay data-link connection identifier (DLCI) values global rather than local significance. DLCI values become DTE addresses that are unique in the Frame Relay WAN. The global addressing extension adds functionality and manageability to Frame Relay internetworks. Individual network interfaces and the end nodes attached to them, for example, can be identified by using standard address-resolution and discovery techniques. In addition, the entire Frame Relay network appears to be a typical LAN to routers on its periphery. LMI virtual circuit status messages provide communication and synchronization between Frame Relay DTE and DCE devices. These messages are used to periodically report on the status of PVCs, which prevents data from being sent into black holes (that is, over PVCs that no longer exist). The LMI multicasting extension allows multicast groups to be assigned. Multicasting saves bandwidth by allowing routing updates and address-resolution messages to be sent only to specific groups of routers. The extension also transmits reports on the status of multicast groups in update messages. Committed information rate Frame Relay connections are often given a committed information rate (CIR) and an allowance of burstable bandwidth known as the extended information rate (EIR). The provider guarantees that the connection will always support the C rate, and sometimes the PRa rate should there be adequate bandwidth. Frames that are sent in excess of the CIR are marked as discard eligible (DE) which means they can be dropped should congestion occur within the Frame Relay network. Frames sent in excess of the EIR are dropped immediately. Market reputation Frame Relay aimed to make more efficient use of existing physical resources, permitting the over-provisioning of data services by telecommunications companies to their