Method for providing connectionless data services over a connection-oriented satellite network by associating IP subnets with downlink beam identifiers

A method for transferring a data message in a connectionless manner between a selected source terminal and a selected destination terminal, in a communications network which uses the Asynchronous Transfer Mode (ATM) and a preselected ATM Adaptation Layer (AAL) Protocol for data message transfers and supports connection-oriented communications, the communications network having a plurality of source terminals, destination terminals and satellites having uplink and downlink antenna beams with one of the uplink antenna beams covering the selected source terminal and a selected downlink antenna beam covering the selected destination terminal, the method comprising the steps of:

• assigning a selected downlink beam identifier to said selected downlink antenna beam which uniquely identifies the selected downlink antenna beam within the network;
• assigning an address to the selected destination terminal of which a preselected portion includes the selected downlink beam identifier of the selected downlink antenna beam covering the selected destination terminal;
• formulating a data packet comprising said data message and said address of said selected destination terminal;
• segmenting said data packet into one or more cells in accordance with said AAL Protocol to generate a plurality of cells, each of which has a predetermined length of which a first predetermined portion comprises a cell header and a second predetermined portion of which comprises a cell body;
• identifying fields within each cell header in accordance with said AAL Protocol, said fields comprising a virtual path identifier (VPI) field, a virtual communication identifier (VCI) field, a header error correction (HEC) field, a cell loss priority field and a payload type identifier field;
• retaining said cell loss priority field and said payload type identifier field in each cell header;
• deleting said VCI, VPI and HEC fields in each cell header;
• identifying new fields in each cell header comprising a cell type identifier field and a downlink beam identifier field;
• formatting each field of each said cell header with sufficient information to route said cells from said select source terminal through said network and to said select destination terminal comprising the steps of:
• placing a predetermined value in each said cell type identifier field in accordance with said AAL Protocol to identify that each said cell is to be treated in a connectionless manner,
• placing a predetermined value in each said cell loss priority field in accordance with said AAL Protocol to indicate a priority of said cell,
• placing a predetermined value in each said payload type identifier field to indicate a last cell of a message in accordance with said AAL Protocol,
• copying the selected downlink beam identifier from the address of the selected destination terminal,
• placing said copied downlink beam identifier into the downlink beam identifier field of each of the cell headers;
• transmitting said cells through one of the uplink antenna beams to one of the satellites;
• using value in said downlink beam identifier field to route the cells in the network to the satellite having the selected downlink antenna beam corresponding to the selected downlink beam identifier;
• broadcasting said cells over the selected downlink antenna beam;
• and,
• receiving said cells by destination terminals located within said selected downlink antenna beam, one of the destination terminals being the selected destination terminal.