Is it the master cylinder or the brake booster causing these issues

I am suspecting the master cylinder has failed but then again I am suspicious about the brake booster. If I have the hose off the booster and feel suction with engine running, what would this indicate? This would be good, correct? Then reconnect to the booster. The pedal goes to the floor and pumping doesn't change anything. The fluid is always full in the reservoir and I have no brakes. I am not understanding how to get the pedal pressure back so I have brakes. I can appreciate any advice. Thank you.