发明名称 |
Remapping of ATM cells for multicast transmission |
摘要 |
Improved methods and apparatus are disclosed for remapping Asynchronous Transfer Mode ("ATM") cells in an ATM switch to convert a single Virtual Path Identifier ("VPI")/Virtual Connection Identifier ("VCI") address pair to multiple outgoing VPI/VCI pairs for multicast transmission. An incoming cell is examined to determine the ports through which the cell will exit and a local header is generated which includes a field specifying the I/O modules ("IOMs") through which the cell will exit. The VPI/VCI pair of an incoming multicast cell is mapped to a global multicast identifier ("MID") which is written into the local header. The cell, including the local header is then forwarded to the IOMs specified in the header. A first lookup table on each IOM is employed to provide a port bitmask indexed by MID to direct the cell to the previously identified ports, and to map the MID into a connection identifier ("CID"). A second lookup table is employed to map the CID provided from the first table to a destination VPI/VCI. The second table is shared among all ports on the IOM. Memory utilization efficiency is improved by using global MIDs and by distinguishing multiport-multicast cells from single-port-multicast cells. If the cell is being sent to a single port within the IOM then a single location is allocated in the second table. If the cell is being sent to multiple ports within the IOM then multiple locations are allocated within the second table.
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申请公布号 |
US5917819(A) |
申请公布日期 |
1999.06.29 |
申请号 |
US19960638117 |
申请日期 |
1996.04.26 |
申请人 |
CASCADE COMMUNICATIONS CORP. |
发明人 |
YANG, BING;HEBB, ANDREW T.;GOSS, GREGORY;MALLOY, PHIL |
分类号 |
H04L12/56;(IPC1-7):H04L12/56 |
主分类号 |
H04L12/56 |
代理机构 |
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代理人 |
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主权项 |
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地址 |
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