Guaranteed Bandwidth using Looped Containers in Temporally Disjoint Networks within the Nostrum Network on Chip

Abstract

In today's emerging Network-on-Chips, there is a need for different traffic classes with different Quality-of-Service guarantees. Within our NoC architecture Nostrum, we have implemented a service of Guaranteed Bandwidth (GB), and latency, in addition to the already existing service of Best-Effort (BE) packet delivery. The guaranteed bandwidth is accessed via Virtual Circuits (VC). The VCsare implemented using a combination of two concepts that we call `Looped Containers' and `Temporally Disjoint Networks '. The Looped Containers are used to guarantee access to the network -- independently of the current network load without dropping packets; and the TDNsare used in order to achieve several VCs, plus ordinary BE traffic, in the network. The TDNs are a consequence of the deflective routing policy used, and gives rise to an explicit time-division-multiplexing within the network. To prove our concept an HDL implementation has been synthesised and simulated. The cost in terms of additional hardware needed, as well as additional bandwidth is very low -- less than 2 percent in both cases! Simulations showed that ordinary BE traffic is practically unaffected by the VCs.