The NetMediator correlates the records of various NetCounters and converts them to a format acceptable to the back-end billing system. Libretto formed the basis for Lucent's Interprenet product. This not only provides correct sharing semantics, but also allows us to establish appropriate reservations automatically on behalf of unmodified legacy applications. Embedded Systems Pebble is a minimalistic micro-kernel from Bell Labs. Pebble is based on the notions of hardware-protected domains and portals.
Threads migrate through portals to different domains.
Portal traversal is fast because it does not involve scheduling. Portal installation in a domain implies authorization to traverse the portal. When a portal is installed, it is specialized to the given client and server entry point. For example, when a client opens a file, the file server might create in the client's domain a portal specifically for reading that given file. Consequently, many run-time checks can be avoided.