What Is Hairpin?

So what is a hairpin? Well, it's not a hair accessory, so don't get too excited. A hairpin is also not a comb you use to style your hair. It's not a type of fish—though it does sound like one. It means something that helps two things come together and work together more efficiently. The name refers to the pin looping back on itself in a U-shape (which is also entirely appropriate). Hairpins are used in telecommunication to help direct calls between different providers or operators within a network. In other words, they let you send your phone back in the direction of its point of origin—like when you try to call your friend, and his phone isn't working. You can wait for him to text you back later or attempt to contact him again. Hairpins are pretty cool. You know how you go to her office when you're looking for a hairpin and can't find one in your mom's bathroom? She's got one in there, but she doesn't know where it came from? Well, that's what happens with hairpins: they appear from nowhere and then disappear into thin air. This is the same thing that happens with telephone calls! In telephony, a single call may be turned into a two-legged call. The two legs intersect at the destination number. The first leg is the call from the source to the destination number, while the second is the call redirected back from the call. The term hairpin was later used in digital data networks to denote an existing feature in some network address translations (NATs) where more than one host is placed behind a NAT. The NAT assigns each host a particular external address and port. So next time someone tells you they're "doing their hair," remember that they could be using an actual hairpin instead of just getting ready for work or school!