other subsystems is via Central Message Controllers, each provid- 32.17 DMS-Link ing up to 70 DS30 ports to the Switching Network and Input/Output Controller. The greater part of one of DMS SuperNode key elements, DMS- Link, is implemented in software. Essentially a software and proto- col structure for use on the signalling links between DMS 32.16 DMS software SuperNode applications and network nodes, DMS-Link delivers specific capabilities to end users on the telephony network to suit a The control component software system provides the software variety of requirements. DMS-Link also includes a standard set of necessary for the basic call processing decision functions; it also application and base interfaces for use in Custom Programming. provides extensive software for the administration and maintenance DMS-Link consists of sets of communicating applications and of the DMS-100 hardware and connecting facilities. There are protocol stacks where the applications are software programs that several thousand software modules consisting of several million provide end-to-end functions and services to the user and the proto- lines of program code. In order to manage the design and production col stacks provide the means of communication between the pro- of reliable software on this scale, the system has the following grams. These protocols include ISDN Access (Q.921 and Q.931) the characteristics: Network Operations Protocols (NOP and X.400) X25 for packet switched communication and Common Channel Signalling System 1. Programming in a high level language. Number 7 (SS7). 2. Programming modularity. Application programs, which can be services or utilities, interface 3. Programming structure. with the top layers of the protocol stacks, and by using special 4. Programming portability. software interfaces, customers can add their own applications to the system as appropriate. The standard software application set curren- Both the Central Control CPU (first generation) and the DMS tly includes call processing, OA&M processi