Hi there, as I stated before: up to my point of view there is no difference between “ip telephony” and “voice over ip”. These are two expressions for exactly the same thing, where “voice over ip” is the more technical expression.
That’s why I was asking for the exact topic of your homework, because I don’t understand why anyone should write a homework to explain a difference that doesn’t exist:-).
Because these two expressions mean the same, they (of course) refer to the same technologies, use the same protocols and have the same advantages or disadvantages compared to traditional telephony, respectively.
Best regards
Frank