How Traceroute Works (Building a Movie Scene 'Trace' Map) - Computerphile 

Ahah, I'm starting to get a feeling that almost everything about the modern internet is a hack on top of things that weren't designed for this. Great video, thank you!

I would like to see the graphics updated with each hop being a different color. It would be clearer when there is a hop. :-)

This dude explains things very well.

Traceroute can take a little practice to use effectively, to help shorten the learning curve I will add that there are three common reasons why we don't get TTL exceeded messages from routers. 1) As mentioned in the video, some operators think sending ICMP messages to external networks is a security risk, so their routers have filters that only send these messages to other routers within their network. This thinking is mostly outdated, at least as it applies to networks meant to host publicly-accessible content, and it's not the main reason we don't get responses. 2) ICMP messages must be sourced from a specific IP address. Some IP addresses are internet routable (AKA, public) and others are not (AKA, private). Routers directly connected to "the internet" (AKA, border routers) usually source these messages from a public IP address, whereas routers within a private network usually source ICMP from a private address. Routers using a private address usually send the TTL Exceeded message, but it get's dropped at the border because of the private source address. This is the most common reason you never hear back from certain routers during a traceroute. 3) Routers can get very busy. Router software places a lower priority on sending ICMP than on routing packets, updating routing tables, etc.. Busy routers are a common reason why you sometimes get a response from a certain router and other times you don't. If you use traceroute to assess packet loss along a route, don't assume that missed TTL Exceeded messages are the result of packet loss.

I've been using traceroute for 20 years and never actually knew how it worked, fascinating!

"Makes its way down to Sydney for the final bit" That's Melbourne. Sydney is roughly where the line comes into Australia. Maybe the drawing is a little messed up, or it took a hop to Melbourne (maybe to join aarnet?) before coming back up to Sydney

Currently covering ICMP in my TCP/IP class and I'm taking a Python class as well. This video could not be more relevant! Love it.

More from this guy please, he's very good at explaining things.

Am I the only one who sees an older version of the Technology Connections guy?

Best explanation I've ever heard about traceroute. Thank you! This is great!

SHEER CO-INCIDENCE! I had begun studying the concepts of IP Packets and network troubleshooting using CMD lately. Overwhelmed to find this top notch video explaining the tracert command in Command Prompt. Thank you so much

"xtraceroute" is (or was) a more advanced version of this Python script: it displays the hops on a 3D globe. The project seems (sadly) abandoned, though.

That classic 2D map scene really reminds me one of my favorite game ever .. uplink from introversion software ..

I have just finished reading this topic. And the video arrives. What a coincidence.

Regarding the paths going through the US: there's almost certainly *more and higher bandwidth* cables running across the Atlantic, across the US and then across the Pacific than across Russia & China or Egypt/Suez & the Indian Ocean.

The person who lives in the middle of America should put up a sign outside their house that says: IP GEOLOGATION IS NOT VERY ACCURAT. and make it large enough to show up on Google maps

One of my favourite Computerphiles ever. Great stuff. I'm also a big fan of QMC. Richard's haircut may have inadvertently put him in the frame for the next Bond villain.

This guy needs to make more videos, he's a good teacher

Whey! It's Richard. I worked with Dr. Richard Clegg during my PhD at University College London. Now at QMUL. 👌

Almost all of those who participate in these Computerphile videos provide little to no background noise or "stuff to look at." Which not only serves as a security measure on their behalf but also as a way for people like me to become less distracted while trying to learn.

Excellent explanation - first time I have heard from this person - hope to hear a lot more from him.

Reminds me of the nights I've spent playing Uplink: Hacker Elite back in 2000s.

The Tor project used to have a GUI called Vidalia that showed the tor nodes on a map that your traffic was using.

Love dot-matrix green papers used in all videos to explain everything.

even if i already knew all of this, this was really interesting to watch, very well done video

That traceroute world trace actually landed in Sydney on the East Coast, then went down to Melbourne

Very good explanation and nicely rendered. I watched paying much attention while on the bus. Regards from Argentina 🇦🇷

10:18 , that a coders whole life

What a massively cool dude! Thanks for the vid.

Would love to see more from Dr Clegg

I don't know if I actually learned anything, but that was really interesting.

One thing that really bugs me when people talk about traceroute is that they never bring up the fact that it does not show you the full picture of the internet routing of your packet, which leads to a lot of misconceptions and misinterpretations about what's going on. You see, packet routing on the internet is inherently asymmetrical, meaning that the path taken from A to B might differ from the path taken from B to A. The chances of A->B being different from B->A increases with the number of hops on the internet. When you traceroute from your machine to a webserver like in the video, it only shows you the A->B path. If you want to know the B->A path, you MUST traceroute from the webserver to the machine, otherwise you'll never know. This is important because sometimes you might get false-positives when, let's say, you're trying to identify which hop on the internet is messing with your packets. There's one such example in the video: when he gets * * * from some hops, one might think that those hops are the ones filtering ICMP packets, because you never see anything beyond them. In reality, those hops might be answering ICMP, but you never get to see their responses because the return path is different, going through another router that actually filters ICMP. Your only chance to pinpoint which router is filtering packets in this scenario is to have a traceroute from the destination towards yourself, and then comparing both traceroutes.

I have spent years in this industry and trying to perfect my cyber skills and no one has explained this topic to me so well.

@14:00 I’m no geographermancer, but I believe that southern point is Melbourne, Victoria.

This sent me down a mental rabbit hole of "what is the center of the USA... say we define that as the point that has minimum collective distance to all other points, yeah probably someplace in Kansas or Missouri or thereabouts... but wait, Alaska and especially Hawaii are going to pull that way off to the north and west... and what about territories, what else do we count..."

AS a computer nerd, i finally understand the asterix results, i never understood this and never googled this result. And i grew up with commodore 64 era. :D

That is an impressive number of GNOME Shell extensions in the top bar

Speaking of traceroute, hello from Lawrence Berkeley National Laboratory!

i was looking for this for quite a while and i see this in my recommended today thanks a lot

Can we get the python code?

There was an article on the news a few days ago about the guy who lives in the middle of the Netherlands, he has that same problem. He even runs an IT company from there, which makes him a more "plausible" suspect.

It's a lot cheaper and easier to put internet cables under the sea than it is to put them across land. If you go overland it's also a lot easier for someone to find and destroy the cable. Even the eastbound routes go via the Mediterranean and via Suez to the Red sea, Indian ocean. Imagine the nightmare of arranging to have super important global infrastructure go through the dozens of countries in the Middle East, with everybody wanting a cut and threatening to cut it off every other day.

Good 'ol Tracer T. Ultimate hacking tool.

You had me at Traceroute and Python 👍

I'm a little giddy to see the Steam icon on his desktop. Even very smart people need leisure

Excellent explanation!!

Is the code available somewhere? It would be a great teaching tool. Of course, so is the video, but that code would be fun to work with. EDIT: Never mind, saw the link in the comments. Damn that "SHOW MORE" - oh wait, maybe Praise that "SHOW MORE"...

This video is great I am however really sick of the adverts

Very Insightful

Maps without New Zealand on them! (the green one, not the UoA one)

Actually brilliant.

0:14 Another world map without 🇳🇿 ... sigh ... 0:37 Mentioning that he wants to ping Auckland just doubles the irony ... 0:44 ... OK, that’s a better map!

Don't be so nervous, you're doing great! :)

Great explanation!!!

We now use Akamai at work for our DNS. Using DigWeb interface you see Akamai and not our servers.

surprised he didnt mention the more useful version of traceroute, mtr.

In the Jeep Super Bowl commercial, The Middle, with Bruce Springsteen features the U.S. Center Chapel in Lebanon, Kansas

I seem to remember that there is a location in the US which continually gets law enforcement rocking up to their door, since it is used as a default location for tracking apps.

Nice explanation

11:10 is this why sometimes I log in from Prague, despite being in Jindřichův Hradec (about 100km southeast)?

Really interesting video!

You have also forgotten to mention that the hop location depends on where the IP address was registered. The test is a good general illustration of how the internet works but the traceroute path is is totally inaccurate.

That was cool indeed

Hey, that was actually really nice. Thanks for sharing :)

The geolocation people should maybe randomize the latitude and longitude to be somewhere within the geographical area generally indicated by the IP address.

Doing great right up to the point he points on the map at Melbourne and calls it Sydney.

What about the box on Big Ben ? The museum at Porthcurno is superb for anyone vaguely into communications

Note that i the modern age, we use IPv6 more frequently. TTL (time to live) has been renamed to hl (Hop Limit)

Awesome video

Sir thanks for clear explanation....I want the videos how wires harkand putty tool works please keep a video on that.....

Geo center of America is unpopulated. Geo center of either South Africa or a specific city was for a while a dude's house. Interesting interviews on RU-vid about the phenomenon described at 12:00 that don't and haven't happen(ed) for geo center of US!

The asterisk more often then not are the huge data centres converging major internet traffic. Ping is rejected there for load reasons you simply don't want any unnecessary overhead. Security reasons are obvious.

Very nice...

7:28 Look at all the 10.* addresses up to step 7. That’s a lot of ISP-internal routing going on!

Thank you

Well explained 🔥

I've tried looking up that longitude and lattitude in the USA (latitude":37.751,"longitude":-97.822) and found it to be somewhere in the middle of Cheney Reservoir, located west of Wichita, Kansas.

My goodness, I thought for a moment he was Ronnie Barker in his 40s. Incredible likeness.

You'll have to update your script to show a 3D view once Starlink comes into common usage ;)

Why does the computer take so long to determine if password is correct at login? Windows and Linux, at least, even when the password is literally blank, takes awhile to come back rejected.

more videos Dr Richard G Clegg

Quick question about Geo tag, Geo fence, etc.. is Geohash a good way to work as unique key for a dataset? I mean it is strong enough to a hash collision etc..

Rooter? Like the drain cleaner ?

On line 74 at 12:42, there is a comma after the word line. Does anyone know why? As far as I can tell, it does nothing but I don't have much experience with python.

Is there not an ICMP trace route functions that is used instead of the time exceeded ICMP message?

Does pathping have the full functionality of both ping and traceroute?

14:12 Cape Town is on the coast, not in the middle of South Africa. The undersea fibres are not over the land.

Hello, Can you guys make a video on pagination? I believe it is an interesting topic and I haven't been able to find relevant videos on your channel. I would be great if you consider that :) Thankyou

I remember back in the day running a traceroute from here in east-coast Australia to... that MP3 website in Russia of dubious legality. I can't remember the name and I guess they're long gone now. Anyway, the route went across the pacific, across the U.S., across the Atlantic into Amsterdam, A few stops through Europe, and into Moscow. Not the quickest route because the internet was and is still very U.S.-centric.

Potwin Kansas... ip center of the US and I can assure you that no one from there is hacking or spamming anyone but they do have some pretty crazy stories as a result. Google the article for an interesting series of unfortunate events.

spaces please around those assignment = signs

Looks like Sydney Uni has moved to Melbourne :)

❤️

When I use my phone as a hotspot (EE network), websites think I'm in Croydon for some reason. I'm not in Croydon. But when I use my home broadband websites know exactly where I am, down to about half a mile, which is a bit creepy.

That last point is very interesting. If we start to have more solar based power, I wonder if the machines will intelligently reroute traffic through routes that are in maximal solar and/or wind green energy while avoiding paths on the shadow side of the planet? Thoughts anyone?

Very cool

a video on why the first 7 hops shown at 8:26 are all private IP ranges could be interesting. You're on a mobile broadband connection, aren't you?

I wish he was a professor at my uni

no captions and autocaptions disabled, sad! Can't watch with audio and no headphones nearby

Gratuitous comment to boost engagement. Plus a duck. 🦆