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Is TCP or UDP better for VPN ?

Generally, TCP is more reliable than UDP, however, UDP performs better than TCP.

TCP is a stateful protocol requiring acknowledgement "ACK" packet to be received for every packet sent. This causes greater overhead on TCP connections, but does make them more reliable.

UDP, on the other haand is a stateless protocol. As such, packets are assumed to be received with no retries or acknowledgements. This reduces overhead and makes UDP quicker, but less reliable than TCP and more prone to packet loss.

Generally, VPN UDP is better for VoIP, media streaming and gaming traffic, as well as high capacity broadband connections where packet loss is unlikely. TCP is better for overall reliability of transmitted data, and slower/unreliable connections (3G/4G/Wireless, Satellite, etc.)

  User Reviews/Comments:
by anonymous - 2014-02-25 03:40
Since you tunnel complete IP packets (including TCP/UDP) inside the tunnel, this makes no difference at all, since all protocols work the same way inside the tunnel and outside. Therefore, you should prefer UDP at all times, since it reduces overhead. The only use for TCP is getting around restrictive firewalls, it has only drawbacks.
by anonymous - 2015-01-22 10:49
As far as broadband connections are concerned, I would agree UDP configuration is fine. I've successfully used a VPN composed of 3 sites, the 2 "leafs" being 20 km and 300 km away from the "centre".
I then ran experiments other 3G network and it's a totally different story. Working with wireless network on a daily basis, I already noticed services over UDP weren't that reliable, for example DNS over UDP is often impaired by "Quality Of Service" : either packets simply get dropped, or round trip takes forever (several seconds, more than what DNS clients generally accept in my embedded context).
So, if you're using a 3G link inside your VPN, and your provider uses QoS to loose or slow down UDP packet, run the VPN in TCP mode. For me it went from useless to perfectly fine.
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