Minimum Bandwidth, Latency and Keep Alive for a Tunnel Client Connection

Question:

What is the absolute minimum amount of bandwidth and the maximum amount of latency required to maintain a successful tunnel client connection to an appliance?

Answer:

An idle tunnel client connection carries only keepalive traffic, which is a small message exchange of one byte per second between the client and server. For regular tunnels, the server sends the Keepalive every 300 seconds and for ESP based tunnel it is the UDP Keepalive interval of 20 seconds. So any latency beyond that would cause problems. Realistically, any network that can provide more than a 9600bps connection should function normally with the tunnel clients, although its low speed may not provide the best user experience.