Large internet environments are increasing the difficulty of network management. Integrating increasing numbers of autonomous subnetworks (each with an increasing number of hosts) makes it more difficult to determine if the network managers of the subnetworks will interoperate correctly. We propose a high level, formal specification language, NMSL, as an aid in solving this problem. NMSL has two aspects of operation, a descriptive aspect and a prescriptive aspect. In its descriptive aspect, NMSL specifies abstractions of the network components and their instantiations, and verifies the consistency of such a specification. The abstractions include the data objects and processes in a network management system. These abstractions are instantiated on network elements. Network elements are grouped together in the specification of domains of administration. An extension mechanism is provided to allow for the specification of new management characteristics that the basic language cannot express. In its prescriptive aspect, NMSL generates configuration information directly from a consistent specification. This information is used to configure network management processes to make their operation consistent with their specifications. Standard management protocols (such as the emerging ISO or IETF standards) can be used to incorporate the configuration information into running management processes.

Procedure calls provide a synchronous interface to call downward through successive layers of abstraction, and remote procedure calls allow the layers to reside in different address spaces. A design is given for distributed upcalls, a mechanism for propagating upcalls across address space boundaries. Distributed upcalls provide a natural complement to remote procedure calls, allowing the user to arbitrarily place abstractions in the server or in the client. A server structuring system called CLAM, which is currently being used to support an extensible window management system, is presented. The CLAM system, including distributed upcalls, remote procedure call extensions to C++, dynamic loading, and basic window classes, is currently running under 4.3BSD Unix on Microvax workstations.>

CLAM is an object-oriented system designed to support the building of extensible graphical user interfaces. CLAM provides a basic windowing environment with the ability to extend its functions using dynamically loaded C++ classes. The dynamically loaded classes allow for performance tuning (by transparently loading the class in either the client or the CLAM server) and for sharing of new functions.