Woodland Hills-based United Online and Covad Communications said Thursday that the two companies are in an agreement where United Online will tap Covad for its NetZero DSL broadband Internet service. Terms of the deal were not disclosed. United Online has recently begun offering its dial up subscribers with the opportunity to upgrade their service to digital subscriber line (DSL) service. According to the companies, United Online intends to launch its expansion of its DSL service, which will now be available to 30 to 35% of its subscriber base, near the end of Q1 2007.