My VOIP phone service ViaTalk recommended I disable SPI (Stateful Packet Inspection) on my router for better performance.
I did a little research and it appears that the primary purpose for this is to prevent DoS attacks which seems like overkill on a home router. Anyways, disabling didn’t seem to improve my VOIP service, but I was uploading a file today and was getting a significant upload speed improvement, maybe 20+%. Downloads seem faster as well. Nice!
Of course, if that is all this option is designed to do, it seems kind of stupid to have it on by default in a home-level router.
Note: On my DLink DIR-655 the option is under Firewall Settings on the Advanced tab.
I should mention it speeds up downloads as well. A friend of mine who lives in Chicago was already getting an astounding 29,877 kbps down and 4655 kbps up. He switched SPI off and it increased to 32, 185 kbps down and 8,328 kbps up!