The content of the communication can be (and many times is) encrypted. Encryption is irrelevant here. You still need addresses of the local and remote to make

The content of the communication can be (and many times is) encrypted. Encryption is irrelevant here. You still need addresses of the local and remote to make the connection happen. That plus some pretty simple heuristics are all that is needed to make an informed guess into the nature of media in transit. You could spin this argument in the other direction and say that the contents in the pipe should be extremely visible and transparent to everybody. It would be a complete violation of privacy, but it will also identify (to everybody) the kinds of traffic flowing and the costs of that traffic in terms of congestion (if any).