| 摘要 |
An inter-machine trunk (IMT) is provisioned between two witches through an ATM network. The IMT includes a number of virtual connections (VCs) and cell slots within each VC for carrying telephone calls. The IMT is established by multiple repetitions of an inter-switch signaling process, each resulting in the creation of one VC. The number of VCs and cell slots for the IMT is selected based on provisioning information from a network operator. The IMT may be either a pre-established IMT ("PIMT") or an on-demand IMT ("VIMT"). A PIMT is a quasi-permanent connection set up and torn down by an operator to provide some guaranteed data-carrying capacity on the IMT. A VIMT is created automatically upon receipt of a call when no connections are available on the IMT. An IMT can use both a PIMT and a VIMT. When a call request is received at a switch, a call processor determines whether the IMT is to carry the call. If so, a VC of the IMT is selected, and a call request message identifying the called user and the selected VC and cell slot is forwarded to the remote switch. Each switch establishes a connection between the selected VC/cell slot and a respective telephony interface circuit to the calling or called party, as appropriate. The VC/cell slots are identified in both switches by Trunk Circuit Identifier Codes (TCICs) allocated when the IMT is established. |
