UDP packets loss at Israeli ISPs during peak hours

[Oleg Goldshmidt]

We are all familiar with UDP vs. TCP tradeoff, but I think it is quite
irrelevant in the context. The OP sees 50% packet loss through ISP#1
and zero packet loss through ISP#2. I do not think that one can claim
that 50% loss is "normal" for UDP and the network works "as designed".
The "upper" TCP will be able to cope with a relatively small loss rate
in the lower layer, but 50% is not reasonable.

What to do may depend on several factors (in no particular order):

1) Is VPN over TCP significantly slower (higher latency) off-peak?
2) Does changing the UDP ports (if at all possible) help?
3) Is ISP#1 a lot cheaper than ISP#2?
4) ISP#1 does not even provide reasonably reliable DNS? Hmm...
5) Can the exact reason for the loss be determined? If it is shaping
then there may be a chance that after a determined complaint things
will get better for a specific customer. If it is overcommitment and
general lack of resources any improvement is unlikely, IMHO. This may
be discovered by playing with ports.

-- 
Oleg Goldshmidt | oleg at goldshmidt.org