The ground controllers of NASA re-established its contact with International Space Station in just less than 3 hours after the computer failure had blocked their communication.
The flight controllers of Houston were updating the ISS software when the data relay system broke down. But ISS was able to irregularly contact NASA through the Russian stations. Usually, NASA communicates to ISS from Houston through three communication satellites.
Interruptions like these have happened certain times in past.
The main problem was that the primary computer that has the responsibility of controlling the critical functions of the ISS defaulted to the backup computer. But it did not allow the ISS to communicate with the Tracking and Data Relay Satellites of NASA.