ACK vs. NAK

When we are sending messages — messages of any sort, be they SMS, morse code, messages in a bottle, waving hello across a crowded street — we need a protocol, a set of expectations for how the exchange of messages will play out.  Key to such protocols are two types of protocol messages, NAK and ACK.

NAK, or “negative acknowledgement,” is a protocol message sent when something’s gone wrong. “I can’t hear you.” “Noise on the line.” “I don’t understand.” “Please explain.” 

ACK, or “acknowledgement,” is a protocol message that signifies ”okay, got that, next…”

NAK and ACK can be used together, but, more often than not, their use anchors two fundamentally different methods for communicating.

Think of giving your credit card number over the phone. You can simply rhyme out the digits — “4111 1111 1111 1111” — and wait for the other party to interrupt or to reply, when you’re done, “could you repeat that.” A NAK, in other words. Or simply to proceed. Which allows you to assume they got the number.

Or you could spool out the credit card number digit by digit, waiting for confirmation from the other party. “4” (they say “4” or “OK”), “1” (they say “4” or “OK”), and so on. ACK ACK ACK.

These protocol messages are not only part of human communication, but also part of the very lifeblood of the Internet upon which you read this post. It comes to you, down in the engine room, via TCP/IP, a “reliable, ordered, and error-checked delivery of a stream of octets between applications running on hosts communicating over an IP network.”

Which is to say, a way of getting these words from my server to your browser in a way that works out for all concerned.

In the human realm the messaging systems we use most often, outside of face to face communication, are email and texting, and in both of these there is a fog of confusion surrounding whether we’re expected to use ACK protocol messages or NAK protocol messages.

I notice this fog most often with generations younger than mine: I will send a text message or email and never receive a reply. I’ve deduced that this isn’t because the message isn’t received, nor because it isn’t read, taken to heart, acted on. It’s simply that younger people than I have switched to only sending NAK when needed, and never sending ACK: they’ll let you know when there’s noise on the line, but otherwise it’s faith-based communication.

The contrast with my generation, which is more ACK-based, is more palpable because many of my peers over-ACK. So they not only reply to messages that cry out for an ACK, but they will often add a coda message, something like “Have a Great Day!” or “Thanks for doing this!” or “Great.” The youngers consider this, from the first ACK onward, wasteful over-communication.

As I sit almost exactly in the DMZ separating the ACKers and the NAKers, I have the most confusing position of all, as I need to decide, on a message by message basis, which way to go. And, especially in recent years, as I try to trend younger and fight off my impending agedness, I opt for NAK. Which is a mistake when there’s a clear expectation of ACK.

This all came to a head in March during a protracted, stressful flurry of ACKnessless for which I was socially called to task.

As a result, I’ve jumped over to the other side, going so far as to not only always ACK, but to prophylactically establish an expectation of impending ACK by engaging in pre-message messaging. “I’m heading to the train station now. I will text you once I’m on the platform and then, again, when the train arrives.” That sort of thing.

If you’re going to commit messaging faux pas, I ration, it’s better to err on the side of being annoyingly over-communicative than annoyingly under-communicative.

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