while I was working today on router, My senior said that since VoIP protocol works on UDP, it doesn't support load balancing, which I couldn't quite understand. Can someone enlighten me on this. We have tunneling/ connection from India office to Australia office, we have 2 ISPs to connect to that location, one ISP as a backup. Because of we use VoIP calls, we cannot use load balacing or something similar.

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The problem with UDP is that it is a simple, connectionless, fire-and-forget, best-effort protocol that has no ordering or guarantees. VoIP and other real-time protocols need to have a reasonably steady data stream that arrives in order.

Load balancing of packets causes jitter and out-of-order packet arrival, both of which are VoIP killers. VoIP can tolerate a fair amount of delay, but it simply can't tolerate much variation in the delay (jitter), not can it tolerate out-of-order packet delivery. Instead of hearing, "Hello," you may hear what sounds like, "Oh, hell."

It may be possible to load balance individual flows.

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