In March 2015, we tried to change the default MTU to be 1400 instead of 1500, to help with achieving more reliable connections across different connection types. This was done by changing the openvpn.json config file on the provider, like this:

diff --git a/provider_base/services/openvpn.json b/provider_base/services/openvpn.json
index 11cb0dc..127f589 100644
--- a/provider_base/services/openvpn.json
+++ b/provider_base/services/openvpn.json
@@ -25,7 +25,7 @@
       "cipher": "AES-128-CBC",
       "keepalive": "10 30",
       "tun-ipv6": true,
-      "fragment": 1500
+      "fragment": 1400
     }
   },

Unfortunately, this wasn't supported by the android client, so it meant that android users were broken.

At one point someone said that this option wasn't supported by the android API, but maybe this has changed?

(from redmine: created on 2015-10-20)