We sometimes think of Google as a search company, but that's merely incidental—Google is really the world's biggest advertiser. That's why the antitrust case focused on Google's ad tech business could have even more lasting effects than cases focused on search or mobile apps. The court ruled against Google last month, and now both sides are lining up to present their proposed remedies in a trial later this year.

In today's hearing, US District Judge Leonie Brinkema set the beginning of that trial for September 22 of this year. Just like the search case, the Department of Justice (DOJ) is aiming to hack off pieces of Google to level the playing field. Specifically, the DOJ is asking the court to force Google to sell two parts of the ad business: the ad exchange and the publisher ad server. The ad exchange is the world's largest marketplace for bidding on advertising space. The ad server, meanwhile, is a tool that publishers use to list and sell ads on their sites.

While Google lost the liability phase of the case, it won on the subject of ad networks. The court decided that the government had not proven that Google's acquisition of ad networks like DoubleClick and Admeld had harmed competition. So, Google won't have to worry about losing those parts of the business.

The government's proposed breakup would come in phases, beginning with a requirement that Google provide real-time access to bidding data to third-party vendors. Google objects to this as it would essentially force the company to develop systems that don't currently exist and then release them as open source products. The timeline for such an effort, the company believes, makes this infeasible.

Following that move, the DOJ wants to see Google sell the aforementioned components of its advertising business. Naturally, Google opposes this as well.

"The DOJ’s additional proposals to force a divestiture of our ad tech tools go well beyond the Court’s findings, have no basis in law, and would harm publishers and advertisers," said Lee-Anne Mulholland, Google's VP of regulatory affairs.