X25 Simulator - management of calls

The purpose of the X25 call simulator is to establish virtual circuits (switched SVC or permanent PVC) using the Signalling link or Data link and to sequence data packets transfers. The X25 call simulator uses the level 3 emulator services provided by the AS-INTERFACE.

Protocol simulation: behaviour

The X25 call simulator can use different link types:

  • a permanent link on Vseries interface (V24, V11)
  • the DL link via the call simulator on SL (ISDN B channel, V24 Hayes).
  • the SL link (ISDN) to establish a permanent logic link or a switched logic link (X31 procedure - case B - incoming access). SL-X25 simulator can be used simultaneously with Q931 call simulator on SL link

The virtual calls are:

  • outgoing if the simulator behaviour is of the Generator type.
  • incoming if the simulator behaviour is of the Responder type.

For each link, the simulator allows to generate automatically up to 50 outgoing calls specified individually and to accept up to 99 incoming calls. The total number of virtual circuits simultaneously established can be 100 (50 outgoing calls whilst accepting 50 incoming calls).
The Responder and Generator functions are not exclusive:

  • their simultaneous validation implies the generation of outgoing calls AND the acknowledge (acceptance or rejection) of incoming calls.
  • their simultaneous non-validation implies holding in the inactive state (no reaction from the X25 packet emulator).

Each call is defined by three STATES:

  • ESTABLISH state which starts with a logical channel allocation,
  • ACTIVE state which corresponds to a possible data transfer on the established virtual circuit,
  • CLEARING state to clear the logical channel.

Protocol emulation: options

The Packet emulator is initialized by the choice of the protocol used (X25/X75) and the operating options (set of parameters).

 

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updated:  27-Feb-04