First, I noticed that a newer generation of Broadcom router SoCs have a flow cache and a Runner network packet processor according to several posts on the SmallNetBuilder forums. While the Runner network packet processor is obviously a hardware packet processor, what does the flow cache do? Does it just cache the results of previously routed packet flows so that if matching packets show up, does it use the results to speed up routing? This obviously means that Broadcom has made two generations of hardware accelerators, with cut-through forwarding and Broadcom Flow Accelerator being in the first generation, and the flow cache and the Runner network packet processor being in the second generation.
Second, does enabling IPv6 disable any of the acceleration technologies that Broadcom has sold into home routers? The reason that I suspect that IPv6 could be a possible incompatible feature on older hardware accelerators is if the hardware accelerators were designed to expect only IPv4 packets so that any non-IPv4 packets could cause the hardware accelerators to fail, forcing the router to use software routing if it is expecting to route non-IPv4 packets. If the hardware is properly designed to sort traffic so that IPv4 traffic is sent to the hardware accelerators and non-IPv4 traffic is sent to the CPU, or if the hardware accelerators can handle both IPv4 and IPv6, then this question is not quite as critical. The reason that I suspect that IPv6 could be a possible incompatible feature is if the hardware was designed to expect only IPv4 packets so that any non-IPv4 packets could cause the hardware acceleration engines to fail, forcing the router to use software routing if it is expecting to route non-IPv4 packets.
Third, the initial post mentioned that port forwarding works by disabling acceleration for affected traffic while leaving the rest of the traffic to be accelerated in hardware, at least for the first generation of Broadcom hardware accelerators. Since UPnP is basically a method of automated port forwarding, is traffic that is enabled by UPnP routed by the CPU with both generations of accelerators?
Fourth, which features entirely disable the flow cache and/or the Runner network packet processor so we know to avoid those features when using a router with these features?
I suspect that I have previously used a rented Verizon Fios Quantum Router model G1100 which has a Cortina Access SoC with its own hardware acceleration that I suspect could possibly be disabled by enabling either IPv6 or UPnP. I have since returned that router when I bought a Verizon Home Router model G3100 with a Broadcom SoC in it, so I cannot test it to determine if either feature is responsible for the poor performance that I had when I had both features turned on. Either the old router or the new router is required for enabling a Fios DVR to connect to the IP network through MoCA. I do not know which hardware acceleration features that it has since Broadcom appears to have at least two generations of actual hardware accelerated routing (generation 1 would be Flow Acceleration, and generation 2 would be the Runner Network Packet Processor), and Broadcom is usually secretive on what hardware acceleration features each SoC has.
Disclaimer: I currently work for Verizon Business as a computer security analyst for a part of Verizon that is not involved with Fios. The views expressed here are my own and are not the opinion of Verizon nor its subsidiaries.
