Analyzing actual Ethernet encoding | Networking tutorial (4 of 13)

In this video, we hook an oscilloscope up to an Ethernet link to see what's going on.
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This video is part 4 of an intro to networking tutorial: • Networking tutorial

[@nbme-answers]

I'm telling you the future of an education is on KZbin. All the best instructors, all the best explanations. Knowledge being liberated before our very eyes! Thanks Ben!

[@nickharrison3748]

Yes..but still Internet is like Encyclopedia. Its a Summary of Knowledge , not knowledge itself. You still have to goto College and Universities to get mentorship of good professors. Yes Ben will be one of them.

[@nbme-answers]

@@nickharrison3748 Any thing that can be taught can be taught on the internet. The internet is the encoding and distribution of information, and information is knowledge. Sure, you have to learn “how to apply it” but that itself is instruction and discovery, all of which is aided by the encoding of information.

[@andrisstuks595]

@@nbme-answers As long as you don't have gaps in knowledge up to the point in the topic what you are interested in - your statement is right, but as an example, you will be unable to calculate derivatives of function if you don't know basic math. So you still have to go to College or University, and when you do so - choose the best one and focus on learning, otherwise, you will become almost specialist of almost any topic without proper knowledge of any of them

[@nbme-answers]

@@andrisstuks595 There is no such thing as not having any gaps in knowledge. There are always gaps. Learning is the process of teaching yourself that gaps exist. As for learning calculus, start here: kzbin.info/www/bejne/d6a7aKGGd9Z3qtU

[@tydon19]

@@nbme-answers I think he meant for "gaps" is at least have an introductory knowledge (prerequisite) about the topic or field you are interested in specially in this type of field or you will get lost

[@misaalanshori]

"Connecting my 8-bit breadboard computer to the internet"

[@Weesy]

omg lmao. My be possible, this dude is insane

[@pcred567]

@@nickadams2361 giving a shit in this world is insane lmao. for real, though, this guy's videos are very insightful.

[@franchufranchu119]

I think the clock frequency is too low, but there might be a protocol for slower computers

[@misaalanshori]

@@franchufranchu119 *_overclock it_*

[@ethananthony94]

@M Isa haha

[@MrTrumanPurnell]

Ben Eater you are THE man

[@ScreenArtUK]

20 years working in IT and never actually visualised this so well .. thanks

[@amyjie2051]

This series is truly amazing. I watched it forever ago and couldn't find it again and was afraid it was lost forever (to me). So glad I found it again. So many tutorials deal with crufty abstractions and networking never made sense until you told me what the wires/bits/frames/packets were actually doing. Many thanks!

[@rmanjit]

Excellent way to represent physical layer data transmission.

[@worstusername22]

Just randomly searched for this, this was a great way to finally see the "physical layer". Great video, thanks. I need to see the whole series from the beginning now!

[@ozzpimp]

This was so incredibly insightful. Thank you.

[@Taha-d2f]

dude I was looking everywhere to find a video like this thank you so much ❤

[@MalamIbnMalam]

So fricken nice! I wish I was taught networking that way lol. This is definitely Networking from an EE Perspective going down another layer of abstraction that you never see when studying Computer Networking in CS.

[@aswinthraj9021]

Hey ! nice video But how do you know that the bit started there. and where are all those sign bit parity bit stop bit and stuff like that?

[@melkiorwiseman5234]

Next video. :)

[@caseylocke4474]

7:50 - "...it reverses the order of the bits." Would you please explain *why* the order of the bits are reversed? Thank you for the great video!

[@shekharnandkoemarsing158]

It's just the way he hooked up the wires to the oscilloscope. Think about it, if that is the side of the sender, then what does the receiver side get first? For example, let's say you want to send me a message in order, let's say the message is "hello". If you send that to me one letter at a time from your side you will send: h e l l o, but at my side what i get first is: o l l e h. I have to first flip the message, or flip the bits as he said, to get the correct message. The graph you see in the video is basically the "o l l e h" from my example, due to the way he hooked up the wiring. Were he to reverse the wires, he would get the correct message right away, just depends from what way you're looking.

[@aristle_]

@@shekharnandkoemarsing158 i think you're confused. packets aren't sent all at once. when i send the message "hello," i begin by sending "h," and you *instantly* receive this (for all intents and purposes), *then* i send "e," which you instantly receive. it's not like feeding a sheet of paper with text on it through a slot where the letters are revealed one at a time in reverse order, it's more like just talking to someone where each sound is continuously received by the other party in the correct order sorry if you figured this out already i'm mostly trying to make sure nobody else gets confused reading this also sorry for being so verbose im high rn oops

[@EugeneWasSeen]

How do you know where one byte ends and another starts on the oscilloscope?

[@EugeneWasSeen]

EugeneWasSeen haha nevermind, that is answered in the next video.

[@trashpanda9075]

@@EugeneWasSeen It was also answered in this video. 6:50

[@Euroliite]

@@trashpanda9075 I rewatched that part and the question was not addressed there.

[@silviomhula5837]

This is just amazing 😉 congratulations and keep ur great work

[@hunterphillips5142]

@@Euroliite 4:50

[@miyukohai1470]

This is awesome, this is something anyone from an electronics background needs to see if they are interested in networking

[@andrewholloway-breward213]

Ben this was amazing, thank you for demystifying this aspect of networking!

[@gudimetlakowshik3617]

BEN....you realize you're giving out all this info for free right? ....excellent content man....I work on ethernet controllers(as a profession) and I never knew this much knowledge goes into these and behind their working.

[@mattt2684]

What about differences in connection speed? For example, my Ethernet connection could be 1000 base t, but my connection speed is only 890 mbps. Why is this and how can the clock still be synchronized?

[@KeithBond]

The link speed of your connection is independent of your computer's ability to transmit/receive to/from it. While your computer is not reading/writing the network the link is "idle". In your case of 1000Base-T this means special "idle symbols" are being squirted back and forth when there is nothing to do. In other words the link is 100% occupied with bits all the time but some of those bits are "filler". !00Base-T uses a similar scheme but if memory serves 10Base-T really does drop to 0v when not in use (except for some frequent link test pulses to keep the link up but they could not be mistaken for data).

[@arnonymous7211]

you sir, are amazing at explaining things. appreciate all your work!

[@wingsonthebus]

This is *gorgeous*. I have that awe-for-science feeling. The only thing I don’t understand is, how did you know where to start reading a byte? I’m guessing it’s part of the contrivance of the situation but I’m still curious how the situation was contrived. edit: haha it was the next video!

[@noweare1]

Yes, that could of been header information, data, etc.... Unless he captures a full packet and decodes it we will never know where KA came from.

[@eloyex]

excellent man !! million years working on this and first time go to physical layer and see the signals ... incredable we are SO result-driven animales !! this make my day .. very happy to see details at board level (almost)

[@cmblcdoe6669]

I have been tempted to get my oscilloscope hooked up to measure Ethernet speeds for some time. I'm glad you did it for me and I can just watch it here. My initial assumption was that when the transmitting end of the wire went high, the entire wire would be high before it changed to low, meaning that data didn't really travel down the wire, but more like the wire as a whole would reflect the current instantaneous state of the signal on it. But your scope shows it changes from high to low in only 50 nS. Assuming electricity (signal) traveling at .8c that would mean the signal would only travel 40 ft in 50 nanoSeconds. That means that a whole nibble (4-bits) can be on a 100 meter length of cable at once. That blows my mind! And that's only 10-baseT or 10mb speed. Imagine gigabit speeds and how many bytes are on the cable at once.

[@noweare1]

Do it yourself. Its not the same as watching a youtube video. KZbin videos are quickly forgotten.

[@spambot7110]

i can see how you could recover the clock frequency and most of the phase from any point in the signal, but i see two phases, 180 degrees apart, that are equally valid. one of those phases is invalidated when the bit values transition between 1 and 0, and it holds for half a cycle. but what if there was just a continuous stream of the same bit? how could it tell if it was a continuous stream of 1s or 0s?

[@spambot7110]

also curious about byte boundaries! i would assume the line code is just responsible for transmitting a string of *bits*, and there's a higher-level coding scheme that aligns the bytes. but then you decoded the line code directly into bytes you sent down the wire, how's that work?

[@titoink]

this is just marvelous !!! great! you sir, have the gift of teaching.Thank you very mucho!

[@nithyavasudevan272]

Dear Sir, I have watched almost every of your videos. I kindly request you to build a series on internet connection on the custom hardware like the 8 bit computer or the 6502 computer. I am currently building a 32 bit computer with vga output and a usb keyboard, mouse input. I am also planing to build an OS for it. From your kind subscriber. Thank you for your kind support.

[@mandaragodagama495]

So that means. I can just connect a oscilloscope to a random ethernet cable and steal data? (Just for knowledge)

[@CieMaKat]

It's worth mentioning that the letter decoding works only because he knows (guessed) which bit is the first one of a byte. If he skip three first bits and start from there he'd get ")h" which could be a valid message.

[@Ghost572]

This is really good. It makes for a good pratice example aswell for decode the signal. Really silly that most texts books i've read never really bring in some real life experiment to the theory, especially when you can do something really basic to make it more relative to a learner.

[@Locane256]

That was excellent, I love your videos. Thank you for making them, but this one especially. I feel like people really get used to understand computers and software in an abstract way and forget that they're made up of really complicated electrical signals at the heart of it all.

[@shubhamkashyap6814]

What about starting and ending bits .or this is just informative video ? How could you so sure the that is exactly the data that you are try to send ?🤔

[@8slabs692]

was searching for this video for long time. so voltage fluctuation is used to denote 0 n 1. i want to know about how 0 n 1 are denoted in all types of cable

[@42escapehatch]

How did you find K and A in the oscillometer!?

[@stupossibleify]

Every video you produce grabs my attention!

[@manzoor4687]

Your voice is really polite and easy to understand. i am impressed, keep up the good work.

[@jonamism]

I just loved this video! Super awesome..hats off to you brother. Now i'll be going back and seeing part 3 of 13 to understand Manchester coding

[@ВоронцовАркадий]

Thank you very much, great explanation!

[@train4905]

Butifull demo sir. I'm an electrician by trade. And I love networking.this is superb.keep up the great work sir.

[@ScuffedLawReview]

Is there a way to tell when the byte starts? If you started recording the bits from a different start point, you wouldn't get 75 and 65. EDIT: It's in the next video lol

[@tomaszstaniewicz7123]

great explanation :) I am curious how to detect where byte actually starts, and what happen if two devices try to transmit parallel over the wire, how is the collision detected? Thank you very much :)

[@zmarssojourner7435]

This guy does crazy/dig-in experiments that I always wanted to do in college!

[@richardwang3438]

Ben, did you write some code to keep sending KA

[@DrBouwman]

I have always wondered how this works. Thanks a million! Can you also say how it works for glass fiber? I suppose that's actually just on off of a laser, or something, right?

[@Bruno-yi4nb]

Why does it reverse the order of the bits? 7:42 - 8:09

[@nikolaikalashnikov4253]

3:38 **Now in the horizontal direction, this is telling us that each division represents 100 nano-seconds** 7:38 **We've decoded two bytes** [ 1101 0010 ] [ 1000 0010 ] 7:42 **And one thing that sorta I guess a little different about ethernet is the way is puts these bits onto the wire in this format, it reverses the order of the bits: The 128th place is sent last, and ones-place is sent first.** So the time-axis must be increasing from left to right ? Sorry, just trying to get this straight in my head. I understand now.

[@stargazer7644]

Yes the sweep goes from left to right

[@BassFenderJazz]

Great video!

[@vurtualboy]

So what I'm confused about is it seems like your oscilloscope is reading 64KHz when measuring the wave. What I want to know is why is that? Is there something I'm missing about how ethernet works? Wouldn't 10Mbps be 10MHz? I'm curious because I want to do the same, and I want to know what quality of oscilloscope I would need to be able to accurately see the data.

[@CyrusBufkin]

you need at least 5x the signal rate to useful analysis, 10x if you want to go into intricate analysis.

[@vurtualboy]

but 64Khz is much lower than 10Mhz...

[@mushfiq814]

Hey. I know I am super late in answering this. What I think is happening is that the oscilloscope doesn't actually detect the frequency of the signal. instead that frequency is the frequency of the visible wave on the screen. It tries to look for a pattern on the screen and calculates the frequency of that.

[@kodalisaisumanthchowdary8935]

If education system hadn't killed the application curiosity in students, this video wouldn't be so underrated

[@eysterous]

короче, если сдвоенная верхушечка (впадина), то это переход от 1 к 0 (или наоборот), а если одинарная, то это "холостой" переход great video!

[@goofypettiger]

Excellent video. Just what I had been searching for!

[@Nandblow]

Best videos. I'm going to watch it all. Thakns :)

[@johnmcgiv1]

Just brilliant thank you Ben I am 70yrs and understood this short explanation first time again brilliant.

[@ligazeltina5387]

Who else went to school to study this and didn't learn it until seeing this video?

[@emiliobenavente1575]

So what is a negative voltage? Is that just electrons going in th opposite direction as originally intended by the circuit, if so how would this be possible, are we just calculating if the copper wire went left a little or right a little by electronic force?

[@jbragg33]

Amazing, thanks

[@Gabzes]

Anyone know why the voltage fluctuates from 1v to .5v or from -1v and -0.5v within a 100ns period?

[@gormster]

Not an electrical engineer but it looks familiar as an audio engineer. If you play a square wave through any high system and look at it in an oscilloscope, you’ll notice it looks “wiggly” like this - you can find plenty of examples online. That’s because of ‘band limiting’ - the process of restricting the frequencies that we send through a cable to just the ones we are interested in. In the case of audio, we’re only concerned with the frequencies we can hear. In the case of networking, we’re only concerned with frequencies that will allow our receiver to decode our signal. Our receiver can only “hear” 10,000,000 transitions per second - 10 MHz. So we don’t need information contained in frequencies much higher than that. So why does it make it wobbly? Well here’s the weird thing: all band-limited signals (which includes all sound, radio and electrical signals) can be represented as a sum of sine waves. In fact that’s more or less how they all behave in nature. So when you filter out the high frequencies, you end up seeing more of the big wobbles from the low frequencies. You haven’t distorted the signal, or made it harder for the receiver to follow - in fact, the receiver can’t tell the difference, just like your ears can’t hear the ultrasonic nuances of squeaking bats.

[@Gabzes]

@@gormster wow thanks for your response ! Makes sense !

[@Guust_Flater]

You have to do that to change 0 to 1 and 1 to 0. Without it you only can send "0" or "1". To send a different symbol (0>1 or 1>0) on the next clockpulse, you have to keep the signal high, or keep the signal low. In theory the signal would not make a little dip and it would be a horizontal line. (The little dip has to do with inflowing current, I think)

[@Gabzes]

@@Guust_Flater Yeah what I'm wondering is specifically why the little dip is occurring.

[@stargazer7644]

Gaboik this explanation is incorrect. These are not square waves. It is a 10 MHz carrier. The data is phase modulated on the sine wave. The squiggles are there because the bit waveforms don’t start at 0 volts. Look at the symbols to the right. The waveform is made up of a sequence of those symbols back to back. When the symbols alternate, you get those little squiggles. The phase of the sine wave is inverting at that point.

[@prashantb421]

I usually don't comment much, but agree with all comments here. Best video series on networking. Awesome.

[@generalmorozzzz]

This is not Manchester Code but rather binary phase-shift keying. I don´t know why you measured a sine wave on an ethernet cable, but usually it looks like this (it´s a square wave): mashhurs.wordpress.com/2015/11/20/manchester-coding/. IMO the changes happen between the 100 nanosecond intervals.

[@ronkessler1599]

Hi Ben, Fantastic amount of information in this video!! I want to replicate your demo for my students. I connected PC to a 10/100 switch (no gateway) and I can see incoming and outgoing packets. How did you transmit data in your example? I can continuously ping another PC but I would like to send a simple message like you did. Thanks so much for your excellent work!

[@Maxlancer]

Some audiophile claim by this video about signal from LAN cable is sine wave not square wave and not present only as binary Data (1,0) they believed High Quality LAN made sound quality better. I lack of knowledge so may I ask is it true?

[@lotethistlethwaite207]

Great vids man. You're excellent at breaking things down.

[@alchemy1]

Has anyone paid close attention to the oscilloscope? Notice that not only the so called values are binary, they are not even remotely crips and flat. Not only that but one other important thing. All lines lean forward in time. There is no quantum jump.

[@GiveMeAnOKUsername]

Can a wire have more than one value at a time - like a wave? If it’s a long wire then given that signal propagation is finite, couldn’t a cable support multiple voltages at a time?

[@DupczacyBawol]

How on earth one can send ASCII 'K' and 'A' through ethernet and catch them their binary signal on osciloscope? I feel uninformed :(

[@dano2169]

You can use Netcat to send arbitrary data

[@stargazer7644]

Send a packet full of them, and odds are you’ll catch part of the data payload.

[@user-sz8rw2pp1s]

I need some help! I'm not sure what I'm doing wrong. I have a Rigol DS1052E and followed similar settings. What do you have the other end of the Ethernet cable connected to? thanks

[@767Steel]

Man, you're awesome. Thanks a lot for these videos.

[@MrPritz007]

hi, what about the IEEE 802.3u signals of 100Mbps? Is the measurement process same?

[@XxMsrSzprzxX]

Brilliant video. No idea wtf I’m doing watching it at 4AM though.

[@bartosik321]

Im having trouble understanding voltages - when the voltage is below zero, does the current start flowing in opposite direction? Can someone explain what is happening exactly?

[@rohithjanardhan4970]

I love these videos so much, I'm not even skipping ads

[@industrialdonut7681]

Can you do this but show how the ethernet protocol actually registers itself when plugged in? Like how you made a video about USB device discovery, as well as showing the normal data transmission protocol. This is just the data transmission part so I want to see how it all starts though xD

[@marcosdelfino9695]

help because i don't understand the "inverting the bit" part if some one could help me i would be grateful: if the bit needs to be inverted for it to make sense because the router physically sended the first bit of the byte first and is being read/decoded by a human from left to right, shouldn't we also switch the bytes, because with the same reasoning the second byte has been writen first so it would be "A,K" instead of "K,A" please explain it to me i think i got it all wrong, sorry about my english.

[@calcen_]

Can someone explain why are we seeing 62.2340 Khz as the frequency?

[@Astromatric]

Is not as simple. Where is the modulation?, how could you transmite 1000bps on 250mhz ?

[@levroibak4343]

Hi, what kind of oscilloscope do you use? It would be really nice if some could tell me the tech details about it (bandwidth, channels, etc.) Thanks in advance!

[@hailsatyr]

I remember studying this at an IT school, but I was too dumb and uninterested to understand this

[@nabeelsherazi8860]

"if we wanna convert this to a REAL binary number" -- ben eater takes his stand on MSB vs LSB encoding lol

[@valenceelectron1673]

Interesting. Does this mean that the ethernet ports inside our devices rely on FPGAs to register the rising edge of a bit (which registers as a 1) and the falling edge of a bit (which registers as a 0) to decode information? FPGAs seem like a good bet because of their speed, which is definitely required for the faster (1 Gbps) protocols.

[@Dygear]

5 years later your answer is - dedicated hardware inside of an Ethernet port is called an ASIC, application specific integrated circuit. FPGAs are nice when you are not sure of the target or if you are not sure that you are finished optimizing. But ASICs are much cheaper to produce so they are used for large scale productions.

[@jdaniele]

As great as simply! You ROCK! Thanks for sharing. 🙏

[@paulodecimo5436]

Hey @BenEater in simple words, what is difference between Encoding and Signalling?

[@MillennialMonk]

This is what I've been looking for. Thank you.

[@coevad3961]

I'm a little confused, you said that the 128th bit was sent last, but if I'm reading left to right, wasn't the 128th bit sent first?

[@SunshineFromWithin]

What's incomprehensible to me is how a device can change voltage over a wire 10 million times per second. How is that possible?

[@vimalathithand917]

Holy shittt ! Now I understand why we need manchester coding ! Thanks a lott!

[@tushar18]

hi Ben, you say; you were trying to send KA. How did you determine that? of all the data that goes out from a laptop OR was it just an assumption?

[@GamalMahdaly]

Tushar Goel apparently, it was programmed to send a specific massage.. Look at the computer, there was a program running

[@egor.okhterov]

I can see the change in the graph with my eyes, but how does this transition actually becomes 0 or 1 when received by receiving device? 🤔

[@und3rgr0undfr34k]

very well explained. Thanks! Subbed!

[@MrPritz007]

When i set 10mbps, all ok but signals are not visible on oscilloscope rather some spikes are visible. What to do?

[@EightCounts]

I thought oscilloscopes go right to left? IE: data on left side of screen occurred before data on right side.

[@seymurmammadov3868]

This video is awesome. Also, can anyone explain to me the concept of the flip? Why does it need to reverse the order of the bits in the first place?

[@devenderbhardwaj6331]

Hii it was great running through these videos. but how do we that now new byte of data will be starting ? how you selected that these two bits will start from that point ? we may mix the bits

[@galahad38]

7:45 Why is the bit order reversed? Is it convention or is there a reason?

[@mayankshrivastava3554]

What does he mean by "ethernet flips the byte", how is least significant bit the most significant one when we write the data?

[@typedeaf]

A year ago when I started watching your videos, I skipped these because I thought it was some Networking turorial... like ...Network+. I thought that was odd, and since I already know that kind of networking, I ignored it. Now, I have built the 6502 computer with a PS2 keyboard, a BB with CRC encoding using logic ICs to xfer serial data to two Nanos, a simple adder, and other fun things from your channel. After doing the PS2, USB and CRC tutorials, I decided to watch these. So glad I did. This stuff is great!

[@jasondefaoite7732]

10Base-T voltage levels should be +2.5V and -2.5V. 100Base-TX is +1V, -1V

[@TheDarkToes]

1000base-t?

[@nngnnadas]

Btw, you are aware you can just reverse the time axis instead, right?

[@KiranBV1]

Thank you. that was really cool !

[@Thulgon]

Your ability to read the decimal numbers after seeing their binary version for a split second left me speechless. I, for one, can't even add 22 + 41 (in decimal) without using my fingers like a first-grader.

[@aurorajunior6328]

Next up ... running Ai on my breadboard computer.

[@mishun]

Hmm, I don't understand how it discriminates whether very long chunk of 10MHz sine wave is a bunch of zeroes or ones (ethernet doesn't have clock line). I haven't actually read 10base-t specification, but from looks of it I'd guess that zero is transition followed by transition 50ns later and one is transition followed by no transition 50ns later, or something like that.

[@silviomhula5837]

I’m in awe of what I just watched

[@labibbidabibbadum]

Why do I think "yeah, it's late - I'll just give Ben a minute and then skip through to the end" and always, always ALWAYS watch every second? Like, this video is a guy talking about a fkn ETHERNET cable, not Pulp Fiction. Why can I not look away?