Tunnels change the network topology. They let routers A and B be logically adjacent even if they don’t have a physical connection. They also let you run one type of network over another type of network.
Example uses:
1. Run IPv6 network over IPv4-only infrastructure.
2. Connect “internal security zone” networks over “external” routers.
3. Logically connect slave devices (such as access points) to a controller.
A VPN tunnel is a tunnel with encryption. So it has all the features of a tunnel while adding data secrecy.
Low latency and low jitter are not on the tunnel or VPN tunnel feature list. The act of encapsulating /encrypting /decrypting may increase latency and jitter. The encrypted traffic may also cause QOS flags in the original traffic to not be visible to the underlying network infrastructure.