Addressing Out-of-order Issue of Congestion-aware Adaptive Routing in Subnet based NoC

Adaptive routing that dynamically selects a less congested output port from a set of minimal or non-minimal paths aids in preventing the network from saturating at an early stage of increasing packet injection ratio. However, routing packet to an alternate route rather forwarding them to the priority fixed shortest route may lead to a situation of delivering packets in out-of-order sequence at the sink node. Here, sorting and reordering all disordered packets at the sink node end becomes impossible due to unbounded buffer size at higher packet injection ratio. This work presents a method of guaranteeing packets' in-order delivery after employing an window based end-to-end flow control policy when the priority fixed minimal route is not available due to congestion of adjacent link or router node. Proposed mechanism shows guarantee on packet's delivery ordering sequence without heavily degrading its network performances. Experiments over several synthetic and parallel benchmark traffics reveal that the proposed mechanism may still achieve higher throughput after increasing their packet length which is very close to the throughput, achieved by the adaptive routing that follows reordering mechanism at the destination node end.