VPN ISIMA / LIMOS✯
We provide 2 ovpn files - Which one to choose? 👇 CLICK HERE 👇
Overview✯
Our OpenVPN servers allow you to connect to ISIMA/LIMOS resources from outside the establishment. This service is intended for teacher-researchers, administrative staff, PhD students, and students.
The documentation has been validated for the following systems:
- Windows 10
- Debian 11/12
- Ubuntu 18.04, 20.04, 22.04
- Mac OS X Ventura
The OpenVPN service for students does not allow outgoing internet access. This is a decision by the ISIMA Management due to security incidents.
The setup is done in 3 steps:
Client installation✯
An up-to-date version of OpenVPN is recommended. We advise you to update your client if you experience connection issues. As of today, the latest client version is 2.6.6
Do not download OpenVPN Connect as it is not the same product
Retrieving OpenVPN configuration files✯
Connect to https://my.isima.fr/ovpn with your account and download the ovpn files:
You can download all the .ovpn files you have access to by taking the ZIP. Alternatively, you can simply download the file you need.
You will find 2 versions of this OVPN file. One uses a TCP connection, the other UDP. It is good to have both installed on your machine to be able to choose which one to use based on what you plan to do on the network or the conditions under which you connect to the internet.
If you experience issues with one file, start by testing the other. Please verify that you have the latest version of your OpenVPN client.
TCP or UDP - How to choose?
Too long; didn't read:
| TCP | UDP | |
|---|---|---|
| My connection is stable (quality home connection, good Wi-Fi reception or wired) | X | |
| I am connected to a low-speed network or with an unstable connection (phone hotspot, poor Wi-Fi reception, old internet setup) | X | |
| I am in a hotel, airport, train station, or on public Wi-Fi | X |
For more precision to make a better choice:
TCP✯
Advantages✯
- High reliability: TCP's error control ensures successful downloads and prevents connection interruptions.
- High compatibility: This means most networks and firewalls work well with it, ensuring broad compatibility. Even in highly controlled networks.
Disadvantages✯
- Lower speed: TCP's error correction mechanism comes at the cost of speed. For each packet sent, the sender must receive an acknowledgment from the recipient before sending more data. This creates overhead and significant delays in a VPN connection.
- Latency / Lag: If you use a somewhat unstable internet connection, latency may occur. For most static data (websites, file downloads, etc.), this latency is both acceptable and preferable. However, for time-sensitive applications such as VoIP, video or audio streaming, it is better to use the VPN in UDP.
UDP✯
Advantages✯
- Handling slow connections: In some circumstances, the overhead created by VPN encryption can result in very low connection performance. Using UDP instead of TCP can speed things up by reducing the additional processing and error correction delays that come with the latter.
- Transmission of time-sensitive data: If you send or receive VoIP traffic (phone call) or live video (videoconferencing) via your VPN connection, it is preferable to opt for UDP. The same applies to video and audio streaming. In all these cases, the UDP protocol is perfectly suited.
Disadvantages✯
- Less reliability: Sending information using the UDP protocol carries the risk of missing or corrupted data when network conditions are not ideal. This can lead to download failures or connection interruptions when errors accumulate to the point of becoming unmanageable.
- Compatibility issues: In some network environments, incoming and outgoing traffic is restricted to maintain network security. The UDP protocol is generally more restricted than TCP. Using it in such circumstances may result in OpenVPN connection failures (hotels, public Wi-Fi, etc.).