Used in place of vendor-supplied host and switch networking code. Each module implements the syntax and state manipulation for a particular protocol. Core serves to provide state synchronization and operational context for the modules as a group. Both core and modules depend on basic services provided by libraries ELIB allows components to run on several commercially available UNIX systems. Address general purpose address manipulation facility.
Protocol facilitates flexible construction of protocol stacks.
Connections are grouped into paths which are identified by the VPI and the port on which they arrive. Each port has associated with it a signalling protocol which maintains the status of the port and handle all of the call setup transactions for that port. Uses registered address translation. Call Setup Call setup processing is divided into three pieces, a signalling head, a router and a signalling tail. The head receives the request from the incoming port.