Method and apparatus for ensuring cell ordering in large capacity switching systems and for synchronizing the arrival time of cells to a switch fabric
AssigneeVelio Communications, Inc.
InventorsMartin Braff, Gopalakrishnan Ramamurthy, William J. Dally
Life of this patent
Estimating the term…
Abstract
Where links between a port module and plural switch fabric slices are of various lengths, a cell is transmitted from the port module to a switch fabric slice in response to a grant. The transmission is delayed by an amount based on a link round trip delay (RTD) value for the corresponding link between the port module and the switch fabric slice, and a predetermined global delay value. As a result of this delay, the cell arrives at the switch fabric slice at a fixed number of cell times (equal to the global delay value) after issuance of the grant, independent of any link lengths.
Claims44
A method for maintaining cell arrival time synchronization between a port module and plural switch fabric slices, where links between the port module and the switch fabric slices are of varying lengths, comprising:
- receiving, at the port module, a grant from a switch fabric slice;
- transmitting a cell from the port module to the switch fabric slice in response to the grant;
- and
- delaying said cell transmission by a delay amount based on a link round trip delay (RTD) value for the corresponding link between the port module and the switch fabric slice, to cause the cell to arrive at the switch fabric slice a predetermined number of cell times after issuance of the grant, independent of link length.
A method for maintaining cell order in a system having multiple switch fabric slices connected to multiple port modules, comprising, at each port module:
- maintaining a separate input queue for each destination;
- storing arriving cells into the input queues, in arrival order and according to destination;
- maintaining an output queue;
- serving grants received from the switch fabric slices by removing cells from the corresponding input queues and transmitting the removed cells to the corresponding switch fabric slices, grants received during a particular cell time being served prior to grants received during a later cell time, and within a single cell time, grants being served over links in a predetermined order;
- and
- storing, in the output queue, all cells arriving from the switch fabric slices during a particular cell time prior to storing cells arriving during a later cell time, and within a single cell time, storing cells in the predetermined order according to links on which the cells arrived.
A switching system, comprising:
- plural switch fabric slices;
- and
- plural port modules connected to the switch fabric slices via links of varying lengths, each port module transmitting a cell to a switch fabric slice in response to a grant received from the switch fabric slice, said transmission being delayed by a delay amount based on a link round trip delay (RTD) value for the corresponding link between the port module and the switch fabric slice, to cause the cell to arrive at the switch fabric slice at a predetermined number of cell times after issuance of the grant, independent of link length.
A switching system comprising:
- multiple switch fabric slices;
- and
- multiple port modules connected to the switch fabric slices, each port module comprising:
- plural input queues corresponding to plural destinations, arriving cells being stored into the input queues in arrival order and according to destination, and
- an output queue,
- grants received from the switch fabric slices being serviced by removing cells from the corresponding input queues and transmitting the removed cells to the corresponding switch fabric slices, grants received during a particular cell time being served prior to grants received during a later cell time, and within a single cell time, grants being served over links in a predetermined order;
- and
- all cells arriving from the switch fabric slices during a particular cell time being stored in the output queue prior to cells arriving during a later cell time, and within a single cell time, cells being stored in the predetermined order according to links on which the cells arrived.
A system for maintaining cell arrival time synchronization between a port module and plural switch fabric slices, where links between the port module and the switch fabric slices are of varying lengths, comprising:
- means for receiving, at the port module, a grant from a switch fabric slice;
- means for transmitting a cell from the port module to the switch fabric slice in response to the grant;
- and
- means for delaying said cell transmission by a delay amount based on a link round trip delay (RTD) value for the corresponding link between the port module and the switch fabric slice, to cause the cell to arrive at the switch fabric slice a predetermined number of cell times after issuance of the grant, independent of link length.
A system for maintaining cell order in a system having multiple switch fabric slices connected to multiple port modules, comprising, at each port module:
- separate input queue means for each destination;
- means for storing arriving cells into the input queue means, in arrival order and according to destination;
- output queue means;
- means for serving grants received from the switch fabric slices during a particular cell time prior to serving grants received a later cell time, and within a single cell time, serving grants over links in a predetermined order;
- and
- means for storing, in the output queue means, all cells arriving from the switch fabric slices during a particular cell time prior to storing cells arriving during a later cell time, and within a single cell time, storing cells in the predetermined order according to links on which the cells arrived.
Dependencies are inferred from the claim text.