ATM adaption layer traffic scheduling for variable bit rate connections

Apparatus for transmitting messages associated with a plurality of variable bit rate connections, each of which is associated with a traffic contract which defines compliance thereto as conformance to a leaky bucket algorithm, said apparatus comprising:

• transmission equipment for receiving multiple messages, said transmission equipment including a segmentation means for segmenting each received message into one or more data units and a multiplexing means for multiplexing such data units from various connections into a single stream for transport over a physical interface at an output transmission rate;
• bandwidth allocation means associated with the transmission equipment for dynamically allocating a portion of the output transmission rate to any connection;
• and
• a scheduler, connected to the bandwidth allocation means, for scheduling the transfer of messages to the single stream of the transmission equipment by one of (a) receiving the messages directly from the connections and transferring the messages to the segmentation means which substantially immediately transfers the messages to the multiplexing means;
• and (b) receiving the data units from the segmentation means and transferring groups of data units to the multiplexing means, wherein each such group corresponds to a message;
• the scheduler being enabled to transfer the messages according to an order corresponding to the level of a leaky bucket associated with each corresponding connection in order to reduce the interleaving of data units from various connections over said single stream.

A method for transmitting multiple messages associated with multiple variable bit rate connections over a network, each such connection being associated with a traffic contract which defines compliance thereto as conformance with a leaky bucket algorithm, said method comprising the steps of:

• segmenting each message of each connection into one or more transportable data units;
• multiplexing the data units from various connections into a single stream for transport over a transmission media to a destination;
• scheduling the transfer of messages from the multiple connections to the multiplexing step and;
• allocating a portion of the transmission media bandwidth to each connection substantially when its message is transferred to the multiplexing step, said portion of the transmission media bandwidth for a given connection being substantially equal to 1/T, T being computed as T ← max ⁡ ( T S + X - τ S N - 1 , T p , T L ) , if ⁢ ⁢ ⁢ N > 1
• and
• T←max(Tp, TL), if N=1
• where TS is a period corresponding to a constant sustained transmission rate, Tp is a period corresponding to a peak transmission rate, τS is a burst tolerance, N is the number of data units in the message, X is a fill level of the leaky bucket associated with the given connection, and TL corresponds to all unused bandwidth allocated to a service class to which the given connection belongs.

A method for transmitting multiple messages associated with multiple variable bit rate connections over a network, each such connection being associated with a traffic contract which defines compliance thereto as conformance with a leaky bucket algorithm, said method comprising the steps of:

• segmenting each message of each connection into transportable data units;
• multiplexing the data units from various connections into a single stream for transport over a transmission media to a destination;
• scheduling the transfer of messages from the multiple connections to the multiplexing step;
• and
• wherein the scheduling step comprises one of:
• (i) scheduling the transfer of groups of data units from the segmentation step to the multiplexing step, wherein each such group of data units corresponds to a message, and
• (ii) scheduling the transfer of messages from the multiple connections to the segmentation step, wherein the segmentation step substantially immediately transfers the data units to the multiplexing step;
• and
• wherein the scheduling step is enabled to transfer the messages according to an order corresponding to the level of a leaky bucket associated with each corresponding connection in order to reduce the interleaving of data units from various connections over said single stream.

Apparatus for transmitting ATM adaption layer (AAL) service data units (SDUs) associated with a plurality of variable bit rate connections, each of which is associated with a traffic contract which defines compliance thereto as conformance to GCRA(TS, τS) and GCRA(Tp, 0), said apparatus comprising:

• segmentation means for segmenting each AAL SDU into at least one AAL segmentation and reassembly protocol data units (SAR PDUs);
• ATM layer means for multiplexing the SAR PDUs of various connections into a single stream having an output transmission rate;
• physical transmission means, connected to the ATM layer means, for transporting the single stream of SAR PDUs over a physical interface;
• bandwidth allocation means for dynamically allocating a portion of the output transmission rate to any connection, and
• a scheduler, connected to the bandwidth allocation means, for scheduling the transfer of SDUs to the ATM layer means, and for allocating a portion of the output transmission rate to each connection at the time its SDU is transferred to the ATM Layer means, said portion of the output transmission rate for a given connection being substantially equal to 1/T, T being computed as T ← max ⁡ ( T S + X - τ S N - 1 , T p , T L ) , if ⁢ ⁢ ⁢ N > 1
• and
• T←max(Tp, TL) if N=1
• where TS is a period corresponding to a constant sustained transmission rate, Tp is a period corresponding to a peak transmission rate, τS is a burst tolerance, N is the number of data units in the message, X is a fill level of a leaky bucket associated with the given connection, and TL corresponds to all unused bandwidth allocated to a service class to which the given connection belongs.

Apparatus for transmitting ATM adaption layer (AAL) service data units (SDUs) associated with a plurality of variable bit rate connections, each of which is associated with a traffic contract which defines compliance thereto as conformance to a leaky bucket algorithm, said apparatus comprising:

• segmentation means for segmenting each AAL SDU into at least one AAL segmentation and reassembly protocol data units (SAR PDUs);
• ATM layer means for multiplexing the SAR PDUs of various connections into a single stream having an output transmission rate;
• physical transmission means, connected to the ATM layer means, for transporting the single stream of SAR PDUs over a physical interface,
• bandwidth allocation means for dynamically allocating a portion of the output transmission rate to any connection;
• and
• a scheduler, connected to the bandwidth allocation means, for scheduling the transfer of SDUs to the ATM layer means, the scheduler being enabled to transfer the SDUs according to an order corresponding to the level of a leaky bucket associated with each corresponding connection in order to reduce the interleaving of data units from various connections over said single stream.