US 5,689,499 A · Method and apparatus for managing the statistical multiplexing of data in digital communication networks

Abstract

An apparatus and method are provided for supporting a plurality of virtual channel (VC) connections within a single virtual path (VP) in a digital communications network operating in the Asynchronous Transfer Mode (ATM). The apparatus (56) is combined with the cross-connected part of a conventional VC switch (54) to form a Data Switch (40). A VP switch (42) switches and terminates incoming bandwidth-resourced VPs on lines (48), some of which are carrying non-bandwidth-resourced VCs and switched onto lines 50 on the output side of VP switch 42. VPs on lines (50) are switched and multiplexed by the Data Switch (40). Buffers (66) store cells and a VP rate server. The buffers (66) are significantly larger than in a conventional VC switch to enable smoothing of data flow peaks associated with data flowing from multiple bandwidth resourced VP tributaries into single resourced VP tributaries. Despite the large buffers in the Data Switch (40) congestion may result when data bursts occur on several converging streams. When buffer overflow is threatened, Data Switch (40) discards whole frames, i.e., whole VPI-VCI sequences marked with an end of transmission delimiter in the PTI, rather than individual cells originating from different frames as with normal ATM cell multiplexing.

Claims19

Dependent claims

A method for supporting a plurality of virtual channel connections within a single virtual path in a digital communications network operating in the Asynchronous Transfer Mode (ATM), where said virtual channel connections have no guarantees of rate at which cells on that connection can be transmitted, but also have no constraint on said rate save that inherent on said virtual path connection, said method comprising the steps of:

storing cells arriving for transmission on said virtual path in a buffer for transmission of cells on said virtual path in conformance with said constraint on said rate;
detecting whether buffer overflow is threatened by the storage of further cells arriving for transmission on said virtual path;
and,
while buffer overflow is threatened, admitting for storage in said buffer cells only on such of said virtual channel connections on which the previous cell admitted was not indicated by the header of said previous cell as being end of transmission on said virtual channel;
and,
at all times not admit for storage in said buffer any cells on said virtual channel connections for which since the previous indication of said end of transmission on said virtual channel connection there has been any rejection of cells for storage.

3 more elements

A method for supporting a plurality of virtual paths on a single physical cell transmission system in a digital communications network operating in the Asynchronous Transfer Mode (ATM), each virtual path supporting a plurality of virtual channel connections, where each said virtual path has an individual rate constraint, the method comprising steps of:

storing cells arriving for transmission on any one of said virtual paths in a common buffer for transmission on said physical cell transmission system;
scheduling the stored cells for transmission on said physical cell transmission system at time instants that conform with said individual rate constraints on said virtual paths, and preserving the order of transmission cells on a said virtual path to the order of arrival for said path;
detecting whether buffer overflow is threatened by the storage of further cells for transmission on any of said virtual paths, and detecting whether said scheduling on a particular virtual path is over a specified limit;
and for any cell arriving for transmission on a given virtual path,
while buffer overflow is threatened or the scheduling for said virtual path is over the specified limit, admitting for storage in said buffer and scheduling for transmission cells only on such of said virtual channel connections on which the previous cell admitted was not indicated by a header of said previous cell as being an end of transmission on said virtual channel;
and,
at all times not admit for storage in said buffer any cells on said virtual channel connections for which since the previous indication of said end of transmission on said virtual channel connection there has been any rejection of cells for storage.

4 more elements

An apparatus for supporting a plurality of virtual channel connections within a single virtual path in a digital communications network operating in the Asynchronous Transfer Mode (ATM), where said virtual channel connections have no guarantees of rate of which cells on that connection can be transmitted, but also have no constraint on said rate save that inherent on said virtual path connection, where said constraint on said virtual path connection is in terms of a specified shortest allowed time interval between successive cells on said virtual path, said apparatus comprising:

means for storing cells arriving for transmission on said virtual path in a buffer for transmission of cells on said virtual path in conformance with said constraint on said rate;
means for detecting whether buffer overflow is threatened by the storage of further cells arriving for transmission on said virtual path:
and,
means for admitting for storage in said buffer while buffer overflow is threatened cells only on such of said virtual channel connections on which the previous cell admitted was not indicated by the header of said previous cell as being the end of transmission on said virtual channel, and wherein said admitting means at all times does not admit for storage in said buffer any cells on said virtual channel connections for which since the previous indication of said end of transmission on said virtual channel connection there has been any rejection of cells for storage.

1 more element

An apparatus for supporting a plurality of virtual paths on a single physical cell transmission system in a digital communications network operating in the Asynchronous Transfer Mode (ATM), each virtual path supporting a plurality of virtual channel connections, wherein each virtual path has an individual rate constraint said apparatus comprising:

means for storing cells arriving for transmission on any one of said virtual paths in common buffer for transmission on said physical cell transmission system;
means for scheduling the stored cells for transmission on said physical cell transmission system at time instants that conform with said individual rate constraints on said virtual paths, and preserving the order of transmission of cells on a said virtual path to the order of arrival for said path;
means for detecting whether buffer overflow is threatened by the storage of further cells for transmission on any said virtual paths, and detecting whether said scheduling on a particular virtual path is over a specified limit;
and,
means for admitting for storage in said buffer and scheduling for transmission while buffer overflow is threatened or the scheduling for said virtual path is over the specified limit, cells only on such of said virtual channel connections on which the previous cell admitted was not indicated by a header of said previous cell as being an end of transmission on said virtual channel, and wherein said admitting means at all times does not admit for storage in said buffer any cells on said virtual channel connections for which since the previous indication of said end of transmission on said virtual channel connection there has been any rejection of cells for storage.

2 more elements

Dependencies are inferred from the claim text.

Method and apparatus for managing the statistical multiplexing of data in digital communication networks

Life of this patent

Method and apparatus for managing the statistical multiplexing of data in digital communication networks

Life of this patent

Abstract

Claims19