Why Networks Connect When Nobody Makes Them

Interoperating is not a duty imposed on operators, it is generally the most attractive option available to them.

The obvious question about a voluntary arrangement is why anybody bothers. If no rule requires a network to connect to others, and connecting costs money and effort, what stops operators from simply keeping to themselves? The answer is that a network's value to its own customers depends heavily on what those customers can reach. A network connected to almost everything is worth far more to the people paying for it than one connected to almost nothing, and the cost of connecting is usually modest against that difference. Operators interoperate because it is in their interest, and that turns out to be a sturdier foundation than obligation.

This logic compounds. Each additional network that joins makes the whole slightly more valuable to every network already in it, which makes joining slightly more attractive to the next one still outside. A convention adopted by enough participants becomes the only sensible choice for newcomers, not because anybody enforces it but because the alternatives leave them isolated. The pull towards a single interconnected system rather than many separate ones has been strong enough to overcome considerable commercial rivalry between operators who compete fiercely in every other respect.

There are limits worth acknowledging. Interest and obligation do not always point the same way. A network with overwhelming advantages might find it profitable to make interconnection difficult for smaller rivals, and the voluntary arrangement offers no automatic remedy when that happens. Defenders of the arrangement point out that such behaviour has usually proved self limiting, since customers value reach. Critics reply that this is a comforting assumption rather than a guarantee. The honest position is that the incentives have held so far and that nothing in the design ensures they always will.