Comcast Corp. filed suit against the Federal Communications Commission Thursday to overturn the agency’s decision to sanction the company for blocking certain Internet traffic. The lawsuit involves a 3-2 decision the FCC handed down in early August that found Comcast’s practices violated so-called net-neutrality principles, and ordered the company to provide more details of its network-management policies within 30 days. The FCC also ordered Comcast to stop by the end of the year blocking traffic related to specific applications, such as file-sharing software that allows users to swap videos. It was the first time the FCC had found a company in violation of the commission’s net-neutrality principles, which lay out consumers’ Internet rights.