4 ms·

Wait, who blocks UDP? I've worked many different angles of the technology world and never heard of anyone blocking something so ubiquitous.

obscurette 4y ago
Many network owners block UDP at borders. It helps a lot in case of amplification DDOS attacks.
p_l 4y ago
It's "useful" trick to force clients to pay extra for "multiplayer gaming support"
- ycuser2 4y ago
  Isn't Youtube using UDP to transfer their video data?
  - steelegbr 4y ago
    They are and there's old firewalls out there that report Youtube traffic as a UDP DoS attack.
  - p_l 4y ago
    Youtube will at the very least fallback to HTTP over TCP for watching (no idea about live streaming). I did a lot of funky things to get around the "drop all UDP" firewall at my first student dorm :)
  - rasz 4y ago
    nope, https from https://rr6---sn-xxxxnel.googlevideo.com/videoplayback?expire=1661275959&ei https://rr6---sn-xxxxnel.googlevideo.com/videoplayback?expir... ......&sig=xxxx&lsig=xxxx&n=xxxx either mp4 or two separate audio/video streams
cpurdy 4y ago
"who blocks UDP?" In the world of virtual machines, UDP is always the first thing to die. Xen on Amazon, for example, would often (and almost always, if there was any load at all?) silently discard most UDP traffic, and this was true for years. VMWare (back when it was still being actively developed and supported) had fairly atrocious support for UDP as well, and the "atrocious support" level was only if you explicitly enabled it and carefully configured it in the first place. In one VM implementation (15+ years ago, so I can't remember which, but probably VMWare or Xen), we determined that the UDP buffer size was a total of one packet (~1500 bytes). So if you wrote a test that sent or received a burst of more than one packet, only one packet out of the entire burst would have greater than a 0% success rate and the rest were lost. Back then, I was testing with UDP on EC2 before EC2 was open to the public. I was working with UDP-based server clustering tech (previously used by Amazon, since acquired by Oracle). Still have the scars. It's been many years, so my guess is that reasonably decent UDP support has slowly crept into EC2 and other common cloud and virtualization environments, and may even be decently supported by now. It needs to be very good to support the transition to HTTP/3 (which coincidentally I'm currently working on).

obscurette 4y ago

Many network owners block UDP at borders. It helps a lot in case of amplification DDOS attacks.

p_l 4y ago

It's "useful" trick to force clients to pay extra for "multiplayer gaming support"

ycuser2 4y ago
Isn't Youtube using UDP to transfer their video data?
- steelegbr 4y ago
  They are and there's old firewalls out there that report Youtube traffic as a UDP DoS attack.
- p_l 4y ago
  Youtube will at the very least fallback to HTTP over TCP for watching (no idea about live streaming). I did a lot of funky things to get around the "drop all UDP" firewall at my first student dorm :)
- rasz 4y ago
  nope, https from https://rr6---sn-xxxxnel.googlevideo.com/videoplayback?expire=1661275959&ei https://rr6---sn-xxxxnel.googlevideo.com/videoplayback?expir... ......&sig=xxxx&lsig=xxxx&n=xxxx either mp4 or two separate audio/video streams

cpurdy 4y ago

"who blocks UDP?" In the world of virtual machines, UDP is always the first thing to die. Xen on Amazon, for example, would often (and almost always, if there was any load at all?) silently discard most UDP traffic, and this was true for years. VMWare (back when it was still being actively developed and supported) had fairly atrocious support for UDP as well, and the "atrocious support" level was only if you explicitly enabled it and carefully configured it in the first place. In one VM implementation (15+ years ago, so I can't remember which, but probably VMWare or Xen), we determined that the UDP buffer size was a total of one packet (~1500 bytes). So if you wrote a test that sent or received a burst of more than one packet, only one packet out of the entire burst would have greater than a 0% success rate and the rest were lost. Back then, I was testing with UDP on EC2 before EC2 was open to the public. I was working with UDP-based server clustering tech (previously used by Amazon, since acquired by Oracle). Still have the scars. It's been many years, so my guess is that reasonably decent UDP support has slowly crept into EC2 and other common cloud and virtualization environments, and may even be decently supported by now. It needs to be very good to support the transition to HTTP/3 (which coincidentally I'm currently working on).