You should have a Internet test program in your Internet settings on your PC. If not you should look into getting one.
And a diagnostic program is in your Internet settings on your XB as standard.
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Up and down speeds (yes you need to consider them separately). NAT type. Signal latency. Data loss rates. Jitter. Also... Are you using WiFi as they are subject to interference. When was the last time you reset your router and then cleared your system's cache to refresh your Internet connection as recommended by all ISP and platform providers.