Hello Davide
that nowaday IP is used instead of ax.25.
Well in the AMPRNet standard, IP sits on top of AX.25 rather than instead of AX.25.
You need to ask yourself whether your particular application needs the added complexity of IP at all. Academically, I am sure it would be nice to be able to route the traffic, but do you _need_ to do that?
For AX.25 in space use, ask yourself whether you need connected frames at all, or could you just deal with UI frames? That would simplify further your implementation.
One problem with connected protocols under the marginal conditions of an amateur link in space (ie, consider fading!) means that the channel can become clogged with retry frames and re-establishing connection. Depending on your application, a UI frame model can circumvent this to some extent, allowing you to implement your own protocol on top of AX.25 UI frames.
73, Howard G6LVB