Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1998-05-20
2001-11-20
Kizou, Hassan (Department: 2664)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S399000
Reexamination Certificate
active
06320858
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to the field of network telecommunications, particularly telecommunications among computers.
BACKGROUND OF THE INVENTION
This invention is concerned with Asynchronous Transfer Mode (“ATM”) switches and more particularly is concerned with data bandwidth creation using cell replication within an ATM switch.
Sending cells of digitized information and data to multiple destinations, in activities such as electronic mail, video distribution or teleconferencing, is achieved in an ATM switch by cell replication. ATM cell replication in the prior art is spatial. Spatial multicast is the replication of cells on physically independent ports of the switch. Logical multicast, according to the invention, is the replication of cells on the same physical port of a switch.
It is an object of the present invention to create a cost effective, manageable process for cell replication.
SUMMARY OF THE INVENTION
Briefly, the invention is an implementation of a logical multicast process and apparatus. The process may be performed in the existing or specially designed hardware. The inventive process is carried out using hardware that includes an Asynchronous Transfer Mode (“ATM”) switch with input ports for receiving cells. Each cell has a header which includes the address fields Virtual Path Index (“VPI”) and Virtual Channel Index (“VCI”). Output ports transmit the cells to their destination. The input ports and output ports are coupled by: a routing fabric, a mechanism for adding a Control Index (“CI”) to each header to direct the received cells to their respective output ports, each CI based on the received port as well as the VPI and VCI fields of the corresponding cell; a lookup table; and use of the CI to control flow through the routing fabric and to update the VPI and VCI on the outgoing cells by use of said lookup table. The inventive ATM switch process further comprises the steps of:
Assigning a block of consecutive CIs, starting at the original base address CI of the original cell for creating new cells whereupon each new cell is assembled with individual VPIs and VCIs and is destined for the same physical output port as the original cell; blocking out N consecutive CIs (where N represents the maximum number of newly created cells, or leafs); taking a cell from a queue, for delivery to the physical port, indexing the new VPI/VCI by the CI number; directing CIs to the lookup table which provides a corresponding predetermined Logical Multicast Offset field (“LMO”) which defines the offset from the base address of the CI of the next leaf of the logical multicast; a zero value indicative that the connection is not a logical multicast connection or that the CI is the last leaf of a logical multicast connection; and repetitively adding said offset to the base address of the cell to index a second VPI/VCI and a second offset added to the first offset and the sum stored until the LMO offset from the last lookup is equal to zero.
Other objects, features and advantages will be apparent from the following detailed description of preferred embodiments thereof taken in conjunction with the accompanying drawings in which:
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King David R.
Krumpoch Mark A.
Lane Scott E.
Strubeck W. Douglas
General Dynamics Government Systems Corp.
Jenner & Block LLC
Kizou Hassan
Yao Kwang B.
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