[pwg]

If you have cable (i.e., Comcast/Cox) then your internet is shared with some number (how many depends upon exactly how the cable company set things up) of your neighbors, and if enough of them are using up the bandwidth, you will see your own connection slow down.

[sushidev]

Yeah. But I observed udp wg traffic 10 times slower. So I would like to know if it’s a known phenomenon to have udp traffic put on serious throttle?

[pwg]

Ten times slower than what?

A relative statement, without an indication of what you are measuring against, is of no value.

[sushidev]

Ten times slower than other types of traffic such as tcp

[pwg]

At the same time?

Then that does sound like your ISP may be de-prioritizing UDP data, or specifically throttling UDP flows to some level 10x smaller than your full bandwidth.

Are you sure, however, that the other end of the VPN connection is not where the slowdown is happening? If that end was the choke-point, you'd still see slower traffic but your ISP would not be the reason.