What's the difference between OPAL transfer and forward methods?

Question

Both work on an existing connection, so to me it seems that they do essentially the same thing, only that one works before the call is accepted? Documentation for the ForwardCall method, http://files.opalvoip.org/docs/opal-v3_14/d4/d8c/classOpalConnection.html#a74974e1d155b636e2f157c0e15c32d67

Is there a way to tell opal to forward all incoming calls, without using the *72 or 21 numbers?

Answer 1

You usually talk about a call transfer if the full call is already established (including audio and or video), while a call forward moves a call that is currently being established (eg. alerting). Both kinds will work on an existing signalling connection.

That being said, in the real world, forwards sometimes work on established calls and transfers also work on alerting calls...