I want to direct your attention to this quite excellent post by /u/Aerandir. The context he wrote that was for a discussion about what the definition of tribe is/should be.

I don't believe the concept of 'tribal federation' is really addressed in that comment, nor is the comment really meant to address it. However, since I have mentioned him by name, it might draw his attention here and he may be able to contribute something on the topic now.