Method and apparatus for explicit rate flow control in ATM networks

In an asynchronous transfer mode (ATM) network, in which virtual circuits (VCs) between source and destination devices establish at least one link through at least one switch, a method for determining a current communication rate (CCR) for an available bit rate (ABR) VC, said method comprising the steps of:

• computing a fair share (FS) value according to the following equation,
• FS=FS+(Av.sub.-- Bw-Ac.sub.-- Bw)/(#Ovld.sub.-- Vc),
• where Av.sub.-- Bw represents the available bandwidth at the switch for available bit rate (ABR) VCs, Ac.sub.-- Bw represents an arrival rate of ABR cells, and #Ovld.sub.-- VC represents a number of active VCs whose current communication rate is greater or equal to the fair share;
• updating an explicit rate (ER) for the VC to a value that is a function of the FS and the CCR;
• and
• updating the CCR to a value that is less than or equal to the ER.

In an asynchronous transfer mode (ATM) network, in which available bit rate (ABR) virtual circuits (VCs) between source and destination devices establish at least one link through at least one switch, at least one switch comprising:

• a VC table comprising a VC state indicative of cell transmission activity through a VC for each ABR VC routed through the switch;
• a control device coupled to the VC table for determining a fair share bandwidth (FS) for the ABR VC, said device maintaining a count of active VCs (#Active.sub.-- VC) through the switch, said fair share determined according to the following;
• FS=FS+(Av.sub.-- Bw-Ac.sub.-- Bw)/(#Ovld.sub.-- Vc), where Av.sub.-- Bw represents an available bandwidth at the switch for available bit rate (ABR) VCs, Ac.sub.-- Bw represents an arrival rate of ABR cells, and #Ovld.sub.-- VC represents a number of active VCs routed through the switch whose current communication rate (CCR) is greater or equal to the FS;
• said FS determined used by a source device to update the CCR of the VC.

In an asynchronous transfer mode (ATM) network, in which available bit rate (ABR) virtual circuits (VCs) between source and destination devices establish at least one link through at least one switch, the at least one switch comprising:

• a VC table comprising a VC state indicative of cell transmission activity through a VC for each ABR VC routed through the switch;
• a control device coupled to the VC table for determining a fair share bandwidth (FS) for the ABR VC, the device maintaining a count of active VCs (#Active VC) through the switch and using #Active VC to determine FS;
• the FS determined used by a source device to update a current communication rate (CCR) of the VC, wherein, said FS is determined according to the following;
• FS=FS+(Av.sub.-- Bw-Ac.sub.-- Bw)/(#Ovld.sub.-- Vc), where Av.sub.-- Bw represents the available bandwidth at the switch for ABR VCs, Ac.sub.-- Bw represents an arrival rate of ABR cells, and #Ovld.sub.-- VC represents a number of active VCs routed through the switch whose current communication rate (CCR) is greater or equal to the FS.

An asynchronous transfer mode (ATM) network comprising:

• a plurality of links which physically connect a source device and destination device;
• at least one switch coupled between links, wherein available bit rate (ABR) virtual circuits (VCs) are established between source and destination devices using the at least one switch and the links, the at least one switch comprising:
• a VC table comprising a VC state indicative of cell transmission activity through a VC for each ABR VC routed through the switch;
• a control device coupled to the VC table for determining a fair share bandwidth (FS) for the ABR VC, the device maintaining a count of active VCs (#Active VC) through the switch and using #Active VC to determine FS;
• the FS determined used by a source device to update a current communication rate (CCR) of the VC, wherein, said FS is determined according to the following;
• FS=FS+(Av.sub.-- Bw-Ac.sub.-- Bw)/(#Ovld.sub.-- Vc), where Av.sub.-- Bw represents the available bandwidth at the switch for ABR VCs, Ac.sub.-- Bw represents an arrival rate of ABR cells, and #Ovld.sub.-- VC represents a number of active VCs routed through the switch whose current communication rate (CCR) is greater or equal to the FS.

An asynchronous transfer mode (ATM) network comprising:

• a plurality of links which physically connect a source device and destination device;
• and
• at least one switch coupled between links, wherein available bit rate (ABR) virtual circuits (VCs) are established between source and destination devices using at least one switch and links, each virtual connection having a VC state, each VC state starting in an inactive state, at least one switch comprising;
• logic for computing the number of active virtual connections (#Active.sub.-- VC), said logic, if the VC state is inactive and a cell arrives at the switch, setting the VC state to an active state and incrementing #Active.sub.-- VC by one, and if the VC state is in a test state and a cell arrives at the switch, setting the VC state to active;
• and
• said logic, after a first predetermined lapse of time, examining each VC state at the switch, and if the VC state is in the test state, decrementing #Active.sub.-- VC by one and setting the VC state to inactive, and if the VC state is in the active state, setting the VC state to test.