Credit-based Shaping Research Articles

Load-balanced Routing Heuristics for Bandwidth Allocation of AVB Flow in TSN

Time-Sensitive Networking (TSN) is a new technology developed from Ethernet that guarantees deterministic transmission of various types of flows, such as Time-triggered (TT) flows and Audio-video-bridging (AVB) flows, in the same network. Currently, Time-aware Shaping (TAS) and Credit-based Shaping (CBS) are widely used for scheduling hybrid flows, where the credit value in CBS is directly linked to the logical bandwidth value idleSlope , which affects the real-time performance of AVB flows. However, as the network scale increases, existing bandwidth allocation methods result in higher computation times and lower allocation success rates. In this paper, the aforementioned problem is addressed by two-step: first, we design a load-balanced routing heuristic (LBRH) to improve the allocation success rate; second, we accelerate the CBS bandwidth allocation by using unified bandwidth allocation scheme, which integrates LBRH and further improves the allocation success rate. Performance evaluation in multiple test cases shows that LBRH can improve the success rate of bandwidth allocation, and the unified bandwidth allocation scheme integrating LBRH significantly reduces the overall execution time while improving the success rate of bandwidth allocation, which is more suitable for large-scale TSN networks with complex routing.

Bandwidth Allocation of Stream-Reservation Traffic in TSN

Time-Sensitive Networking (TSN) evolves from Ethernet AVB in which the Credit-Based Shaping (CBS) is employed to guarantee the deterministic transmission of traffic. In CBS, the real-time performance of traffic associated with the credits can practicably settle the uncertainty of queueing and forwarding for stream-reservation traffic. Hence, the optimization of bandwidth allocation under the CBS becomes a key point to ensure guaranteed performance in the network. In this paper, a bandwidth allocation method is proposed for stream-reservation traffic while the real-time requirements are satisfied. We first illustrate the significance of appropriate bandwidth allocation for traffic under the CBS and construct a general schema for its bandwidth allocation. Also, the influences of the protected window for Control Data Traffic (CDT) on stream-reservation traffic are considered in our method. Further, mathematical models are constructed to analyze the delay bounds and backlogs of traffic to form the feedback for the optimal bandwidth allocation process. Finally, two node-level cases with different bandwidth utilization and a synthetic industrial networking scenario are carried out to demonstrate our method. The results confirm that the excessive reserved bandwidth does not necessarily decrease the delay bound, especially under the high traffic loads scenario. A more desirable bandwidth allocation strategy under the CBS mechanism is that the reserved bandwidth should be just enough according to the traffic loads to ensure the deterministic transmission of traffic.