Where can I get the address of a private network that is accessible over the public Internet? Is it appropriate to send a datagram over the public Internet if the datagram includes the address of a private network? Explanation.

Skype is a well‑known VoIP system used not only for peer‑to‑peer conversations but also for audio and video conferencing involving three or more callers. Assume a video conference with a central server on Skype has N callers, and each caller generates a constant data stream at rate r bps. How many bits per second does the call initiator need to send?  How many bits does each of other N‑1 callers need to send?

The four TCP/IP abstraction layers have me baffled.

At what point in time should inquiries into queuing protocols be initiated?