Asynchronous transfer mode switching network using waiting buffers for routing high service grade cells during congested traffic

Claim 3

An asynchronous transfer mode switching system for serving user stations belonging to different service classes according to different grades, each of said user stations transmitting a cell indicative of a service class of the associated user station, comprising: a plurality of line circuits associated respectively with said user stations, each of said line circuits being capable of translating a channel identifier contained in a cell from the associated user station to a logical channel number; a plurality of first buffer; self-routing switch means having a plurality of incoming line terminals to which said line circuits are connected and a plurality of outgoing line terminals to which said first buffers are connected, said switch means routing said cell to any one of said outgoing line terminals depending on the logical channel number of said cell; a second buffer connected in a circuit leading from one of said outgoing line terminals of the self-routing switch means to one of said incoming line terminals thereof; overflow detector means connected to said first buffers to determine whether a storage level of one of the first buffers desired by said cell is higher or lower than a predetermined storage level when said cell is indicative of a service class of higher grade than that of a predetermined service class; routing control means associated with said line circuits for receiving cells from said user stations for determining logical channel numbers of the received cells according to information contained in the received cells, changing the logical channel number of a subsequent cell indicative of the service class of higher grade when the storage level is determined by said overflow detector means as being higher than said predetermined storage level so that said subsequent cell is routed from a respective line circuit through said self-routing switch means to said second buffer, and changing the logical channel number of the cell in said second buffer when the storage level is subsequently determined by said overflow detector means as being lower than said predetermined storage level so that said cell is routed from said second buffer through said self-routing switch means to said one of the first buffers.

Claim 4

An asynchronous transfer mode switching system for serving user stations belonging to different service classes according to different grades, each of said user stations transmitting a cell indicative of a service class of the associated user station, comprising: a plurality of line circuits associated respectively with said user stations, each of said line circuits being capable of translating a channel identifier contained in a cell from the associated user station to a logical channel number; a plurality of first buffer; self-routing switch means having a plurality of incoming line terminals to which said line circuits are connected and a plurality of outgoing line terminals to which said first buffers are connected, said switch means routing said cell to any one of said outgoing line terminals depending on the logical channel number of said cell; a second buffer connected in a circuit leading from one of said outgoing line terminals of the self-routing switch means to one of said incoming line terminals thereof; overflow detector means connected to said first buffers to determine whether a storage level of one of the first buffers desired by said cell is higher or lower than a predetermined storage level when said cell is indicative of a service class of higher grade than that of a predetermined service class; routing control means associated with said line circuits for receiving cells from said user stations for determining logical channel numbers of the received cells according to information contained in the received cells, changing the logical channel number of a subsequent cell indicative of the service class of higher grade when the storage level is determined by said overflow detector means as being higher than said predetermined storage level so that said subsequent cell is routed from a respective line circuit through said self-routing switch means to said second buffer, and changing the logical channel number of the cell in said second buffer when the storage level is subsequently determined by said overflow detector means as being lower than said predetermined storage level so that said cell is routed from said second buffer through said self-routing switch means to said one of the first buffers.

Claim 5

As asynchronous transfer mode switching system as claimed in claim 2, wherein said overflow detector means further detects a total volume of the storage levels of said first buffers, and wherein said control means is responsive to the detected total volume of the storage levels for rejecting a cell indicative of the service class of higher grade if said total volume exceeds a predetermined value.

Claim 6

An asynchronous transfer mode switching system as claimed in claim 2, wherein each of the user stations which belong to the service class of higher grade transmits each subsequent cell following reception of a cell from a destination user station acknowledging receipt of a previous cell.

Claim 7

An asynchronous transfer mode switching system is claimed in claim 4, wherein said second buffer is capable of storing cells substantially equal in number to the number of user stations which belong to the service class of higher grade.