The name and the number

Ten o’clock. The button goes live under the thumb that has been hovering over it since 9:58, and Case taps it.

The phone now holds a small parcel of everything the form said, and one address to send it to: traversal.com.

Two roles, forty thousand times over

In this exchange, Case’s phone does the asking, and somewhere far away a machine belonging to Traversal does the answering. That makes the phone the clientConcept · lights on your mapclientThe application or device that asks for information or an action. A browser, a mobile app, a smart TV. It is a role in a conversation, not a kind of machine; the same computer can be a server in a different exchange. and Traversal’s machine the serverConcept · lights on your mapserverThe software or computer that receives a request, does the work, and answers. Also a role, not a species. When Traversal’s machine calls out to somebody else’s payment system, it becomes a client for the length of that conversation.. The words describe the direction of the asking and nothing else, and this morning forty thousand clients in kitchens and break rooms and one very quiet open-plan office are all turned toward the same few servers at the same time, asking.

The name is for you

traversal.com is an address written for people — a domainConcept · lights on your mapdomainA human-readable name for a service on the internet. google.com, wikipedia.org. Registered, owned, and pointed at the machines that actually provide the thing, so that people never have to know where those machines are.. It exists so that Case never has to know anything true about Traversal’s machines: not where they are, not how many there are, not that last year there were fewer.

The network does not deliver to names. It delivers to an IP addressConcept · lights on your mapIP addressA numerical identifier, like 142.250.72.14, that networks use to route information to the right destination. The number that a human-friendly name ultimately stands for., which is to say a number, and nobody involved this morning has typed one.

The directory in between

So before the parcel moves at all, the phone quietly asks a directory. The directory is DNSConcept · lights on your mapDNSThe Domain Name System, the internet’s phone book. It turns domain names into the numbers machines route by. Its answers are cached at several layers for speed, and when DNS breaks, perfectly healthy sites become unreachable, which is why it stars in so many outage stories., and the question is small: what number does traversal.com stand for? The answer usually comes from somewhere close by that remembered it. Forty thousand people asking one directory the same question in the same instant would be its own kind of race-day problem, and the remembering is how that problem never happens.

The whole lookup costs less time than the space between two of Case’s heartbeats. Now the phone has a number, and that is the entire event.

The parcel can leave. Before it does, the address on it deserves one slow read.