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Development and Implementation


The initial physical layer network control protocol design was done using Maisie [19], a C-based parallel programming language. It facilitates creation of entities which execute in parallel and the ability to easily send and receive messages between entities. A Maisie emulation of the entire network was developed which uses the actual NCP code. This helped build confidence that the design of the Network Control Protocol was correct.

The network control protocol code was initially tested with only the two packet radios available. Since at least three packet radios are necessary for a complete RN-ES-RN orderwire connection, the next step involved emulating the packet radios via TCP/IP over Ethernet, and completing the development of the code. The packet radio emulation also allowed testing of various configurations that helped determine if the network control protocol was scalable.

The physical layer of the Network Control Protocol is a single-unit consumable resource system. There can be no deadlock since there are no cycles. All message interactions take place with a master switch, except for the initial MYCALL packet broadcast.

The GPS system was also emulated to provide the appearance of mobility so that hand-offs of a host from one ES to another could be tested. The GPS emulation is also an important component of the Virtual Network Configuration Algorithm. The actual orderwire code is used in these emulations.

Steve Bush
Tue Nov 12 11:48:31 CST 1996