When debugging ICE issues it might be very helpful to be able to see from which iteration of SDP renegotiations a given ICE candidates is/was from. Example: I looked at a service which only handed Firefox ICE candidates after the very first offer-answer exchange. Once ICE was established renegotiations were done, but the remote side never provided new candidates. The ICE transport stayed up, because the renegotiations never changed the bundled ICE transport. But it took me quite some time to understand why I would see ICE candidate pairs and a working call, but no ICE candidates in the remote SDP at all. Note: if we add for example the SDP version numbers to the ICE candidate pairs table we should only take the number from the Firefox side, as most implementations fail to properly increase the number in their SDPs.