Are there any advantages to disabling FastTrack on firewall?

RouterOS Beginner Basics
1

I know that you need to disable FastTrack in order to use simple queues, but if you’re just running a plain vanilla setup with the exception of running cake in queue trees on the bridge and wan with no marks, is there any “accuracy” (or other!) advantage to letting the router’s cpu handle everything, rather than enabling FastTrack?

I have FiOS 1 gig internet up/down with an RB5009 connected to the ONT. The RB5009 handles all routing with ethernet running from 5 of its ports to various locations in the house which go into switches for various tvs/etc. and to 3 plume pods which handle wifi for the house.

It all works fine… nothing is broken… I should just leave it alone… this is all just for my edification and to satisfy morbid curiousity… but I’m curious if it’s potentially “better” to disable FastTrack if your router is able to handle the internet speeds without FastTrack, or if it’s always better to keep FastTrack enabled if you’re not using any options that would not work along with FastTrack.

Put another way… are there any potential disadvantages to enabling FastTrack if your router can handle its work with its cpu(s)?

2

It’s not entirely clear what exactly ROS device does when processing fasttracked packet. Most likely nothing much (replacing IP addresses and port numbers for NATed traffic might be it). So by enabling fasttrack you may loose some minor functionality that stateful firewall might provide (e.g. tracking TCP sequence number or detailed flags tracking). So possibly you may become more vulnerable to some MITM attack (a simple L4 firewall that ROS comes with doesn’t really protect you as sophisticated MITM attacks mostly work on higher layers).

If your gear can handle traffic without enabling fasttrack, then you probably want to leave it disabled. At least you’ll have same IPv4 and IPv6 performance (IPv6 fasttrack doesn’t exist yet).