Mac 13.5.1 (Ventura) enables Apple Private Relay by default. At a high level, Private Relay provides a kind of VPN for Safari but also tunnels the TCP traffic over a UDP-based QUIC tunnel, which bypasses the TCP acceleration built into the Viasat network. This drawing shows how Viasat TCP acceleration gets bypassed when a VPN is in use:
See VPN over Satellite - Project Faster for more.
What is the impact on performance? Here is a speedtest result using Safari with Private Relay Disabled:
And here with Private Relay enabled:
Upload speeds take much longer to reach their maximum and the maximum after 15 seconds of the test is a little lower
a. In the case without Private Relay, the speed is almost immediately at the max speed of 5 Mbps
b. but with Private Relay, the speed takes most of the 15 seconds of the test to get to 4.5 Mbps
Download speeds ramp more slowly and also top out at a speed below the maximum supported by the Viasat network.
Disable “iCloud Private Relay” in your Mac or iOS settings
Use a web browser other than Safari