Nielsen NetRatings and comScore have agreed to attend a summit organized by the Interactive Advertising Bureau to sort out differences over online audience measurement practices, according to IAB. Since IAB president and CEO Randall Rothenberg issued his critique of the companies’ respective measurement models in two open letters last month, both NNR and comScore have agreed to undergo an independent audit by the Media Ratings Council audit, and in NNR’s case, full accreditation. During the summit, the IAB said it will continue to press both for full MRC accreditation and ask for a definite timeline on that process.