When using my Roku box via the Mikrotik (wired), apps are much slower than if I do it directly to the fiber box(wirelessly). I do have the fiber interface in bridge mode. For example, peacock takes almost a minute to load to the mail screen via the Mikrotik, well it takes about 20 seconds directly. Bandwidth looks fine on the Roku box and bandwidth and ping tests look fine using other devices.
Any idea where to start on this one?
Thanks

Packet capture shows a lot of resends.

Is your fiber line using PPPoE or anything that might have the lower MTU on the WAN?

If you had another cable that might also be worth a try. And/or perhaps the Mikrotik is using 100Mb/s speed.

Doing a ping from my Raspberry Pi, (directly connected to the router), 1472 was the highest MTU that succeeded.

Which interfaces and which MTU settings do I change the MTU on?

Thanks!
(The router definitely is not at 100, as I get speed tests at over 300)

1472+28 = 1500, so I guess that's not it.

Is it slow just on startup?

I have seen issues with rokus and RSTP. If you are using RSTP, or RSTP is enabled on your device/bridge, set the bridge port that the roku is on to edge=yes

/interface/bridge/port/set edge=yes interface=etherX

Somehow, the Roku delay was caused by the drop !LAN firewall rule. Once that was removed, the Roku is fine and I tested by re-enabling the rule again and the delay came back. I still have a drop WLAN rule and I am still unable to get into the router web screen from the internet using my external IP. Has such, I hope that I am secure still.

I still do see the packet resends, but I see the same when I connect to the fiber gateway. Has such, I need to follow up regarding the gateway.
Thanks

Beyond the firewall stuff...

I'd also be checking IPv6, a lot of streaming services prefer it...and the more recent defaults enable it by default. So could be trying IPv6, then failing back to IPv4... (or it uses IPv6 because IPv4 was being blocked by !LAN)

Very weird, when I disable the drop for !LAN many dns queries fail. They succeed once I re-enable it. Any ideas?

Thanks

It sounds like the issue might be related to the firewall settings on your Mikrotik router. Try disabling the firewall on the Mikrotik temporarily and see if the DNS queries succeed. If they do, then the issue is likely related to the firewall settings.