Flow control in a cell switched communication system
First Claim
1. A method of generating a bandwidth allocation variable for writing into resource cells by a network element in a cell switched connection system, said network element comprising a switch, said method comprising the steps of:
- (a) calculating a cell rate variable which is a function of an aggregate value of bandwidths allocated to active sources connected to said network clement which are directing cell streams to one particular output port of said network element, the bandwidth allocation of the active sources being extracted from said resource cells; and
,(b) determining an overload factor for said output port as a function of a rate of input of cells to said output port in relation to a desired rate of input of cells to said output port,wherein said bandwidth allocation variable for each active source is set as said cell rate variable multiplied by said overload factor.
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Accused Products
Abstract
In a cell switched communication system in which a source is connected to a network for transmission of cells to a network destination via a network element having a plurality of ports, said source generating resource cells containing information concerning a bandwidth allocated to the source for transmitting cells, a method of providing flow control at the network element comprises the steps of: (a) detecting a resource cell as it is received at an input port of the network element; (b) routing the resource cell to a resource cell processing means common to all the ports of the network element; (c) modifying information contained in the resource cell concerning the bandwidth allocation for the source on the basis of a determination of current utilisation of ports of the network element; and, (d) passing the modified resource cell to an output port of the network element for subsequent return to the source. Resource management (RM) cells received at an input port of a network element in an ATM communication system are routed to a centralised resource cell processing means where information in the resource cell relating to the bandwidth allocation of the source is modified to take account of the available bandwidth. The RM cell is subsequently passed back to the source to enable the source to modify its transmission rate to correspond to the modified allocated bandwidth for that source and thereby ensure that cells are not discarded by the network element due to traffic congestion.
49 Citations
7 Claims
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1. A method of generating a bandwidth allocation variable for writing into resource cells by a network element in a cell switched connection system, said network element comprising a switch, said method comprising the steps of:
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(a) calculating a cell rate variable which is a function of an aggregate value of bandwidths allocated to active sources connected to said network clement which are directing cell streams to one particular output port of said network element, the bandwidth allocation of the active sources being extracted from said resource cells; and
,(b) determining an overload factor for said output port as a function of a rate of input of cells to said output port in relation to a desired rate of input of cells to said output port, wherein said bandwidth allocation variable for each active source is set as said cell rate variable multiplied by said overload factor. - View Dependent Claims (2, 3, 4, 5)
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6. A network element comprising a switch having a plurality of input ports and output ports for use in a cell switched communication system of the type where network sources generate resource cells containing information relating to a bandwidth allocation for said network sources which may be modified by said network element and passed back to said source to control traffic congestion at said network element, wherein said network element further comprises a computer programmed to generate a bandwidth allocation variable for writing into said resource cells in accordance with a method of generating said bandwidth allocation variable for writing into resource cells by a network element in a cell switched connection system comprising the following steps:
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(a) calculating a cell rate variable which is a function of an aggregate value of bandwidths allocated to active sources connected to said network element which are directing cell streams to one particular output port of said network element, the bandwidth allocation of the active sources being extracted from said resource cells; and
,(b) determining an overload factor for said output port as a function of a rate of input of cells to said output port in relation to a desired rate of input of cells to said output port, wherein said bandwidth allocation variable for each active source is set as said cell rate variable multiplied by said overload factor. - View Dependent Claims (7)
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Specification