Content-Type: text/shitpost

Subject: The Physical Layer
Path: you​!your-host​!wintermute​!wikipedia​!hardees​!brain-in-a-vat​!am​!plovergw​!ploverhub​!shitpost​!mjd
Date: 2017-12-15T13:17:34
Message-ID: <>
Content-Type: text/shitpost

Gilberto: “Hey, Jo, can I ask you a question?”

Joanna: “Shoot.”

G: “In the OSI network model, why is 2 the lowest layer?”

J: “What?”

G: “Transport is layer 4, network is layer 3, data link is layer 2, and it stops there. Why 2 and not 1?”

J: “It doesn't ‘stop there’. 1 is for the layer below the data link layer.”

G: “They reserved the number 1 for future use? That seems like a clear YAGNI. What did they think they were going to come up with? And why didn't they reserve all the odd numbers? What if they wanted to stick something between 3 and 4?”

J: “They didn't ‘reserve 1 for future use’, they used it. It's the physical layer.”

G: “The what now?”

J: “The physical layer. You know, like whether you're using cables or wireless.”

G: “That's stupid. You send the same octets in the same order regardless of whether you’re using cables or wireless.”

J: “There you go. You can't actually send an entire octet at once.”

G: “Sure I can, that's how it's done.”

J: “No, because the wire can only send one bit at a time.”

G: “One bit? That can't be right. Why not?”

J: “Because the bit is represented in the wire as a pulse of high or low voltage.”

G: “Okay, so why not represent eight bits at once?”

J: “Voltage doesn't work that way. The wire only has one voltage.”

G: “Why not?”

J: “I think it's somehow connected with quantum physics.”

G: “Seriously, you want me to believe that a bit can be represented as some abstract quantum property that only physics eggheads understand? I mean, I can believe it's possible in theory, maybe as some weird kind of steganography, but why go to the trouble?”

J: “I can't believe I'm hearing this. How did you think the packets got from one endpoint to the other?”

G: “It's perfectly simple. The layer 2 peer on one side transmits the frames, and then the layer 2 peer on the other side receives and reassembles them. There doesn't need to be anything in between.”

J: “Well, that's sort of the point, isn't it?”

G: “How do you mean?”

J: “The whole point of the layer 1 – layer 2 boundary is to insulate the higher layers from having to know about the stuff in layer 1.”

G: “I guess, but then why not also have a layer to insulate the higher layers from having to know what flavor of ice cream you're eating when you send the packet? It might be related, but it isn't really part of the network.”

J: “The cables aren't part of the network?”

G: “Are they? We have wireless networks, so the cables can't be that important.”

J: “Without the cables, the bits won't get from one data link peer to the other. The data link peers think they're talking to each other, but really they're talking to the layer 1 peers on the same side.”

G: “This is very far-fetched. Why would they put in three completely unnecessary communication boundaries between the layer 2 peers? It doesn't make sense.”

J: “They're not unnecessary! Information can only be transmitted at the physical layer!”

G: “Bah, next you'll be telling me that information can only be stored at the physical layer.”

J: “Actually yes.”

G: “Okay, then answer this: how do you know it isn't actually stored at some even lower layer below the ‘physical’ layer?”

J: “That is a puzzling question for philosophers, maybe, but actual engineering practice shows that one only needs to go down to layer 1.”

G: “Oh, I get it! It's a hack!”

J: “I guess you could call it that.”

G: “I hope someone is doing research into some more elegant solution to the problem.”

J: “I would like to hear what sort of ‘solution’ you imagine there might be.”

G: “Hey, I'm a software guy. Dealing with this physical universe bullshit is not my problem, that's for the system administration department.”

Punch line: Gilberto and Joanna are brains in vats.