Network Scheduler Port FIFO Packing for Small Data Units
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Solution Overview
Problem
Network devices face inefficiencies in handling smaller data units due to constraints on the maximum service rate of schedulers, which can lead to underutilization of port bandwidth and potential burst behavior.
Innovation Solution
Implementing a scheduler that temporarily increases the service rate for ports when serving smaller data units by using port FIFOs and pseudo-ports, allowing for back-to-back scheduling of these units while reverting to the default rate for larger units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the scheduler enforces a default maximum service rate for all ports, then the system maintains stability and simplicity in scheduling, but smaller data units cannot be transmitted at full line rate causing bandwidth underutilization
Solution Approach 1:
The invention segments the scheduling mechanism by introducing a separate port FIFO buffer for each port that operates independently from the main scheduler. This FIFO handles smaller data units at line rate while the main scheduler continues to enforce default service rates for larger units, thus segmenting the bandwidth allocation based on data unit size without complicating the overall scheduling architecture
Solution Approach 2:
The port FIFO acts as an intermediary component between the scheduler and the transmission interface. It receives smaller data units directly from the scheduler and transmits them at line rate without being constrained by the default maximum service rate, thereby mediating the conflict between maintaining scheduler simplicity and achieving full bandwidth utilization for small packets
2Productivity
If the scheduler allows back-to-back scheduling of smaller data units at increased service rate, then throughput for small packets improves, but burst behavior may increase causing network instability
Solution Approach 1:
The invention applies local quality by allowing increased service rate exclusively for smaller data units that fit within the port FIFO buffer capacity, while larger data units continue to be scheduled at the default maximum service rate. This localized adjustment improves small packet throughput without causing system-wide burst behavior that would compromise network stability
Solution Approach 2:
The port FIFO dynamically adapts its transmission rate based on the size of data units available for transmission. When smaller data units are present, the FIFO transmits them at line rate to maximize throughput; when larger units are present, it reverts to the default service rate, thus dynamically balancing throughput optimization with network stability
3Productivity
If the scheduler services ports at higher frequency for small data units, then bandwidth utilization increases, but the complexity of rate management and control logic increases
Solution Approach 1:
The invention extracts the rate management complexity from the main scheduler by creating a separate port FIFO for each port that independently manages transmission of smaller data units at line rate. This extraction removes the burden of dynamic rate adjustment from the scheduler, maintaining its simplicity while achieving high bandwidth utilization through the FIFO's autonomous operation
Data Source
AI summary
A scheduler in a network device serves ports with data units from a plurality of queues. The scheduler implements a scheduling algorithm that is normally constrained to releasing data to a port no more frequently than at a default maximum service rate. However, when data units smaller than a certain size are at the heads of one or more data unit queues assigned to a port, the scheduler may temporarily increase the maximum service rate of that port. The increased service rate permits fuller realization of a port's maximum bandwidth when handling smaller data units. In some embodiments, increasing the service rate involves dequeuing more than one small data unit at a time, with the extra data units temporarily stored in a port FIFO. The scheduler adds a pseudo-port to its scheduling sequence to schedule release of data from the port FIFO, with otherwise minimal impact on the scheduling logic.