Hi everybody,

Just wanted to give a quick update to the community. After an exhaustive research this week, we identified a memory leak in the Linux kernel which was leading to slower performance for ProtonVPN. In the past two days, we have patched most of the most badly impacted servers, and are working to patch the rest of the server fleet over the next couple days. The problem became more noticeable over the past two months as we had increased load during the COVID lockdowns. We have now significantly improved the granularity of our monitoring to also be able to detect kernel level issues like this.

We are confident that this should improve the speeds on many servers around the world. We are also in the process of buying additional bandwidth in many locations globally which should further boost speeds. Over the course of investigating the speed issue, we also made a number of interesting discoveries which we will further leverage to improve performance further.

We discovered that on Windows, OpenVPN can be rather CPU intensive. As it is single threaded, this means that on some devices, the speed is limited by CPU and not by our server speed. This is partially due to the fact that likely many VPNs, we use AES-256 instead of AES-128 as the default. In theory, AES-128 should also be secure enough, but we like to be extra secure. We will look into making some compiler optimizations for Windows which could reduce the CPU usage and allow higher speeds to be achieved.

We also discovered that there are a small number of paid VPN servers which are sharing the same network as free servers. As free servers have become more congested, this means that some paid VPN servers are also slowing down. We are now also in the processing of separating the impacted networks to prevent free users from impacting paid user performance in these cases.

We are also aware of a macOS bug which causes brief disconnects. This is an Apple bug which has already been reported, but unfortunately has not yet been fixed, and impacts all IKEv2 VPNs: https://developer.apple.com/forums/thread/84920?answerId=252931022

When this problem manifests itself, the VPN will disconnect for a few seconds before automatically reconnecting. While the problem used to be quite rare, in recent macOS releases, it has become more frequent and noticeable.

Unfortunately, we are losing faith in Apple's ability to fix this (just like they haven't fixed the critical security issue we reported to them). We will make some changes to mitigate the impact of this from our side, involving activating the kill switch during brief disconnects (if you don't already have the kill switch activated). But as a longer term solution, we will be switching our macOS app to use OpenVPN as the default.

We're hard at work on all this and hope to have an update for the community again soon. Thanks again for your patience and understanding during this period.

Best,
The Proton Team