Others have suggested a talking stick, and I'll improve on that - a talking stick + timer. Because you need to enforce both 1 person talking at time, and time box them.
Even better, you make the timer be the talking stick. Every time you hand off the timer, you reset it for the next person. They say their piece and reset/handoff to the next person.
I've done this for daily standups/sprint meetings where things were getting out of control, it works well.