International Business Machines Corporation

Alain Saurel

Alain R Blanc

Bernard Brezzo

Pierre Debord

Michel Poret

Patrick J Jeanniot

Sylvie Gohl

Jean-Claude Robbe

A flow control process for a switching system having at least one switch core connected through serial communication links to remote and distributed Protocol Adapters or Protocol Engines through Switch Core Access Layer (SCAL) elements. For each input port i, the SCAL element contains a receive Protocol Interface corresponding to the adapter assigned to the input port i and a first serializer for providing attachment to the switch core by means of a first serial communication link. When the cells are received in the switch core, they are deserialized by means of a first deserializer. At each output port, the cells are serialized again by means of a second serializer and then transmitted via a second serial communication link, to the appropriate SCAL. The SCAL contains a second deserializer and a transmit Protocol Interface circuit for permitting attachment of the Protocol Adapter. The flow control process permits two flow control signals, a flow control receive (FCR) from the core to the SCAL, and a flow control transmit (FCX) from the SCAL back to the core. For transmission of the FCR signal in response to the detection of local saturation in the switch core, the process causes transfer of an internal FCR signal to the serializer located within the saturated core. The FCR is introduced in the normal data flow to be conveyed through the second serial link to the remote SCAL corresponding to the saturated input port of the core. An internal control signal can be transmitted to the Protocol Interface that is originating too many cells which results in the overloaded input port of the core. For the transmission of the FCX signal in response to the detection of a saturated Protocol Interface element at one output port, the process generates an internal control signal to the serializer located in the SCAL element. The serializer can introduce a FCX signal in the normal data flow which is conveyed to the core and then decoded by the deserializer in the core. Thus, the core can be informed of the saturation condition that has occurred in the considered output port. Particular adaptations are provided in which the switching system is arranged in a set of individual switching structures mounted in a port expansion mode.

Flow control process for a switching system and system for performing the same

A switching system having at least two switch fabrics. Each fabric has a switch core and a set of SCAL (Switch Core Access Layer) receive and transmit elements. The switch cores are preferably located in the same physical area but the SCALs may be distributed in different physical areas. Port Adapters distributed at different physical areas are connected to the switch fabrics via a particular SCAL element so that each switch core can receive cells from any port adapter and conversely any port adapter may receive data from either switch core. Control logic assigns a particular switch core to one port adapter for normal operations while reserving the other switch core for use when the first core is out of service. Each switch core has a mask mechanism which uses the value in a mask register to alter a bitmap value which controls the routing process. The mask registers in the two switch cores are loaded with complementary values.

Switch system comprising two switch fabrics

A switching system receives a data cell from a set of n input ports for routing to one or more output ports in accordance with the contents of a bitmap value retrieved from the cell upon its receipt. The system has a module comprising a shared buffer for storing the cells which are to be routed and a mask mechanism with a mask register for altering the value of the bitmap before it is used for controlling the routing process. As a result of operation of the mask mechanism, a cell is either transported to an output port or discarded. Two switching systems are combined in first and second switch fabrics, each having a switch core and a set of switch core access layer (SCAL) elements. Each SCAL element respectively comprises a SCAL Receive element and a SCAL Xmit element for permitting access to input and output ports of one of the switching systems.

Switching system including a mask mechanism for altering the internal routing process

A method and apparatus for managing contention in a self-routing switching architecture based on a set of n&times;n individual switching structures that are connected in a port expansion mode by means of fan-out and fan-in circuits providing access of the Switch Core Access Layer (SCAL) to the different input and output ports of the switching core. The fan-in circuits use an arbitration mechanism for providing a token to the switch that is allowed to deliver the next cell and the arbiter operates from a detection of a special comma character in accordance with the 8B/10B coding scheme which is introduced in the data flow between the individual switching structures and the fan-in circuits. This provides a compensation for the difference in transfer delays of the cells even when high switching speed and long length of the physical media are involved.

Method and apparatus for managing contention in a self-routing switching architecture in a port expansion mode

A switching system comprising a switching structure for routing cells from a set of M input ports towards a set of M output ports. The system includes a set of distributed individual Switch Core Access layer elements which communicate with one input and output port of the switching structure by means of a set of serial communication links. Each SCAL element provides attachment to at least one Protocol Adapter and comprises a set of circuits. The receive part of each circuit, which includes at least one first FIFO storage for storing the cells being received, receives the data cells from the attached Protocol Adapter and introduces at least one extra byte to every cell. Each transmit part of the destination circuit, which includes at least one second FIFO storage having a greater capacity than the first FIFO storage, receives all the cells that are generated at the corresponding output port and uses the at least one extra byte for cell buffering. Additionally, each distrubuted SCAL element comprises control means for performing Time Division Multiplexing access of the FIFOs.

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Nice, France

Alain Saurel