Network tap

A network tap is a device that copies the traffic on a network link for inspection without disrupting normal operation ¹.

Passive taps observe without interfering, for example by optically splitting the light in a fibre; active taps interact with the traffic, for instance by re-timing it or modifying headers to reduce covert channels ¹. RAND's verification framework includes mutually vetted devices that intercept data exchanged between accelerators and check it for discrepancies with declared uses ². In proposed designs such as network taps and certifiers, verifier-controlled taps hash and timestamp the traffic as cryptographic commitments rather than exporting plaintext, so that the prover's declarations can later be checked against them ^{1 3}. Cankaya describes taps on the front-end links between a data centre and the outside world as the most viable, because those links carry little bandwidth ¹. The back-end fabric between accelerators has far higher bandwidth and strict latency requirements, and may call for random sampling rather than full capture ¹.