Guaranteed Rate Port Scheduler Bandwidth De-rating
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Network protocols like Ethernet face under-runs (gaps) in data packet transmission when the combined bandwidth of destination ports exceeds the device's capability, leading to inefficiencies and potential data loss.
Innovation Solution
A guaranteed rate port scheduler (GRPS) that dynamically de-rates the statistical bandwidth of each destination port in proportion to the device's diminished capacity, ensuring only manageable ports are served simultaneously and introducing idle times to maintain balanced transmission rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the device serves multiple destination ports simultaneously at their full bandwidth rates, then the data transmission capacity to each port is maximized, but under-runs occur when the combined bandwidth exceeds the device's capability
Solution Approach 1:
The scheduler dynamically adjusts the service rate for each destination port based on current device capacity and port priorities. Instead of serving all ports at fixed full bandwidth rates, the system continuously adapts transmission rates to match available capacity, preventing under-runs while maximizing overall throughput through flexible rate modulation
Solution Approach 2:
The system changes the operational parameters of destination ports by de-rating their statistical bandwidth in proportion to the device's diminished capacity. This involves adjusting transmission rates, time slots, and service allocations dynamically, transforming the static full-bandwidth assumption into a flexible parameter-based allocation that prevents capacity overflow
2Reliability
If the device de-rates the statistical bandwidth of transmit ports to match available capacity, then under-runs are eliminated, but the total data transmission throughput is reduced
Solution Approach 1:
The scheduler implements partial action by serving only a subset of transmit ports at any given time based on available capacity, rather than attempting to serve all ports simultaneously at full rate. This selective partial service ensures reliable transmission for active ports while accepting that not all ports can be served at maximum capacity concurrently
Solution Approach 2:
The system uses periodic time-slicing where transmit ports are served in alternating intervals rather than continuously. Each port receives periodic service opportunities proportional to its de-rated bandwidth allocation, ensuring fair distribution of limited capacity over time while maintaining transmission reliability through structured periodic scheduling
3Reliability
If the GRPS serves only a subset of transmit ports at a given time, then the device can handle the transmission load, but idle times are introduced reducing overall efficiency
Solution Approach 1:
The scheduler performs preliminary actions by pre-calculating optimal port subsets and service allocations based on predicted traffic patterns and capacity constraints. Before idle times occur, the system proactively reconfigures which ports are active and adjusts their service rates, minimizing the transition to idle states and optimizing the use of available capacity in advance
Solution Approach 2:
The system maintains continuity of useful action by ensuring that when one subset of ports completes transmission, another subset is immediately activated. This overlapping and seamless transition between port groups eliminates true idle periods, keeping the device continuously productive by maintaining a constant stream of active transmissions across different port combinations
Data Source
AI summary
A guaranteed rate port scheduler (GRPS) is used for serving multiple destination ports simultaneously without under-runs, even if the total bandwidth of the ports is more than the bandwidth capability of the device. Certain network protocols, such as Ethernet, do not allow “gaps” (called under-runs) to occur between bits of a packet on the wire. If a network device is transmitting packets to several such ports at the same time and the combined bandwidth of these ports is more than the device can source, under-runs begin to occur within the transmitted packets. The disclosed GRPS solves this problem by: (a) the GRPS serves only as many destination ports at a given time as can be “handled”, and (b) the GRPS fairly selects new destination ports to serve after every end-of-frame data packet transmission by effectively “de-rating” the statistical bandwidth of each destination port in proportion to the diminished capacity of the device.