I would very much appreciate any help with this issue. I'm struggling to understand why my MacBookPro running macOS Big Sur is seeing such a slow connection to my Synology DS1815+ NAS. I have connected the MBP directly to the NAS over Ethernet (no switch, no router). I can access the NAS and mount a shared folder. WireShark outputs an apparently large number of TCP Dup ACK errors while I do that: WS01.pcapng
I can access the mounted folder, and running a LAN_SpeedTest shows ~600Mbps/~700Mbps rates, which seems pretty good. The issue is when I try to run a TimeMachine, CarbonCopyCloner, or Chronosync backup. All those processes just crawl - at best I'm seeing ~10Mbps rates. And WireShark continues to stream large numbers of TCP Dup ACK errors. I'm at the limit of my troubleshooting ability at this point - internet searches haven't helped.
Any advice would be very much appreciated. Thanks in advance.
