[vlovich123]

There are other ways of accomplishing this like doing staged rollouts without giving up the cost efficiencies of implementing your own network only once and avoiding a combinatorial explosion in testing complexity.

You can sometimes play this game with vendors because you want them to give you an interoperable interface so that you avoid vendor lock-in and have better pricing, but that’s a secondary benefit and staged rollouts should still be performed even if you have heterogenous software.

[kortilla]

Staged rollouts do not protect you from long lurking bugs. Even in this ATT case they most certainly did do a staged rollout just because they couldn’t just shut off the entire phone network to run an update across all systems.