A good protocol for multiple master and one slave

[jakaranda]

If I would like to set up a protocol with multiple masters and only one slave, what would be my best option if trying to avoid very long messages (like with Modbus) and also avoiding collisions?

I was thinking an I2C bus, but I've never ste one up, so if anybody has opinions about it or if anybody has a different option, please let me know.

Thanks.