Hello, and welcome back to CS615 System Administration! This is week 5, segment 5, and we're going to be talking about a few of the physical aspects of the internet. We saw in the last video that there's a logistical component to the internet. There's a non-profit governance body for at least some aspects of it, and we also noted that there's a geographical division: certain IP space is allocated to specific geographical regions. --- Now this has necessarily _political_ implications, and we'll get back to those a bit later, but having moved on from the abstract structure of IP packets to how addresses are allocated, let's now take a look at just how packets flow. By that, we don't mean "how do we route packets" -- although that's also interesting and relevant and something we'll discuss in the future -- but we actually mean: "how does a packet get from A to B" -- physically. So we’ll start - down here at the bottom of the stack. --- Now if you have a point-to-point link, then it's rather obvious what path the packet takes. Packets go in here, packets come out there. You can follow the physical cable from one end to the other. --- Even if we're talking communications between your laptop and your wifi access point, it's still reasonably easy to understand the connection. Once the packet arrives at the access point, it then goes into the cable, and then from there... --- ...it is delivered from your ISP to some switchport in a machine room or data center somewhere, where... --- ...let's just say, the packets enter the matrix. At this point, most people start to lose the overview of what's going on -- even CS majors may only have an abstract idea of what the internet looks like at this level, and --- claiming that it's a series of tubes is really not that terrible an analogy as people like to ridicule it to be. After all, we _are_ hooking up cables here and there and packets flow through them, taking turns, being redirected, and so on. --- But the internet is a _global_ network. It's easy enough to imagine physical cables being run across the country between buildings, and you can of course correlate a lot of the data flow with population, which is why most of the action does happen just exactly where you see lights here on this image from NASA. But now let's think about where we find the largest spots of concentration here, and just how are we going to get our packets from - here to there? But it turns out that's really not a new problem -- we've been trying to get communications between the continents for hundreds of years now. In fact, --- we've been doing that since the 1850s, when people first started stringing reaaaally long cables across the ocean floor to enable telegraph communications between America and Europe. And just like back then, we --- still do just that, which I find fascinating. That is, we're actually running these long, loooong cables from one country to the other by dropping them on the ocean floor using these huge, special-purpose ships that have thousands of kilometers of network cables roled up in these huge coilѕ, and which are buried on the ocean floor with special submarine cable ploughs. But they are not always buried, sometimes they are just left on the ocean floor, but yeah, that's what we do. It's simultaneously high tech and yet still obviously simple -- a really long cable. And this is one of those physical aspects of the internet that is useful to keep in mind, because there are a number of implications: on the one hand, you can't possibly get a faster network connection than... well... with a distance of roughly 5800 kilometers between New York and Paris, and the speed of light being almost 300 thousand kilometers per second means that a roundtrip packet cannot possibly be faster than 40 milliseconds, though of course there's some overhead and we haven't quite reached pure light speed between any two points. --- But anyway, so we've been stringing cables between countries, cables known as the submarine internet cables. They are operated by different companies, including communications providers as well as some of the internet giants. This website here -- submarinecablemap.com -- allows you to zoom in and inspect all the various cables, which is really interesting. But think about what this means -- running a cable on the ocean floor. There's all sorts of things that can go wrong with a network cable just sitting there, right? One thing that's pretty interesting here is that of course these cables carry electrical signals, and many animals have pretty acute electrical sensors, so --- it's really no surprise that they will every now and then get curious about what this long string on the ocean floor is all about. And there have been cables that were damaged by curious sharks, because when you're a shark, and you sense something of interest, what are you going to do? You take a nibble to see just whether or not you should eat the thing - you know, might be tasty! But you know what else can happen when you have a cable sitting there out in the open? Well, think about where these cables are run: --- As we can see, these submarine cables are not only out in the open ocean, but often times are closely hugging the coastlines, where there's a lot of industrial ships carrying cargo, and what do ships do when they are waiting outside a city's harbor? They throw their anchor down, which scrapes across the ocean floor to keep the boat from moving. And such an anchor may actually _cut_ the internet cables by accident, which in turn may lead to significant internet outages. But let's take a closer look - at some of these cables here. As you can tell, there's quite a lot of them. Let's pick... this one here. "Havfrue/AEC-2", which connects Denmark, Norway, and Ireland to the United States, an almost 8000 kilometers long cable run by a consortium including Facebook and Google, able to carry 108 Terabytes / s. The landing point in the US is right around the corner from Stevens, in the illustrious Wall Township, New Jersey, run by the New Jersey Fiber Exchange or NJFX, where several cables land: The CONFLUENCE-1 cable, running down the East Coast, for example, as well as the SEABRAS-1 cable, which goes all the way down to Brazil, over 10,000 kilometers in length! Over here on the other side of the US, we have cables crossing the Pacific Ocean, such as the Japan-US cable, which makes a pitstop in Hawai`i. And over here, in... Karachi, Pakistan, we see the "South East Asia-Middle East-Western Europe" cables, which run from Singapore to France, and which, in a major global internet outage taking place in 2008 were accidentally cut, leading to several countries at least partially losing internet connectivity. So as you can tell, there's a significant risk of severe impact if these major communication lines are disrupted, whether by accident or by intent. --- Now of course you may have heard this quote by John Gilmore: "The Net interpreted censorship as damage and routes around it." which attempts to stress the benefits of the by and large distributed nature of the internet, but unfortunately, this is not entirely true. That is, - if you are committed, in a position of significant power, and willing to accept the consequences, then you certainly _can_ censor or disrupt the internet for a large portion of your citizens, and dictators and authoritarian governments have been increasingly making use of their powers here. As I'm sure you're aware, people in power are quite afraid of the common people's ability to communicate freely, and so the internet necessarily represents a great threat to them. Whenever there's a revolt, an uprising, or political upheaval, you can bet that the government in power will try their best to suppress the people's ability to communicate with one another. --- Just yesterday, there was an example of Myanmar cutting off its people from the internet amidst the public protests of the coup d'etat by the Myanmar military in February. What you see here is a graph of the average network connectivity in Myanmar. Since early February, the local ISPs had been ordered by the military to block Facebook, amongst other sites, with increasing blocks since then. --- But this is not a rare occurrence: every day, governments are willing to pull the plug and cut off their own people off the internet, such as Iran in 2019, when the Supreme National Security Council ordered a complete blackout during the ongoing protests there at the time, which was one of the biggest, complete shutdowns for a large country like Iran. But it's not just authoritarian countries like these; --- India, the world's most populous democracy, is currently the sad - leader in the number of internet shutdowns, where the government frequently orders parts of the internet to be turned off or restricted. India holds the sad record of having imposed - the longest shutdown in history, when the Jammu and Kashmir region was put into a "pre-emptive lockdown", which - after 6 months incurred a cost of over 2.4 billion dollars and half a million jobs, illustrating that access to the internet at this point really is a basic human right that governments are unfortunately increasingly willing and still able to restrict at will. If you control the legal entities in charge of physically moving packets back and forth, you _can_ restrict people's access. But such power does not merely extend to a binary on-or-off state off the internet. --- Rather, you are able to access all of the communications flowing through the physical devices that you control. And so if you have the legal power to force even a private enterprise to eavesdrop on all packets zipping by, then it's no surprise that governments like that of the United States also do this. What you see here is "Room 641A", a secret network closet in AT&T's SBC Communications Building in San Francisco. Or rather, it _was_ secret until an employee at AT&T noticed that for some reason there was this locked room that apparently all network traffic was mirrored in. The employee who noticed this was - Mark Klein, who then became a whistleblower alerting the public to the fact the the US government performed warrantless spying on not only global communications -- as just about any large intelligence agency does -- but also wiretapped and data-mined US citizen's communications. And all of this is to once more iterate the point that no matter how much we may focus on bits and bytes and software and system administration, at the end of the day - we are still all operating on layer 9 up here. All the work we do is inherently political: work on the internet enables or prohibits the free flow of information, connectivity and routing and network protocol design all must take into account accidental or intentional abuse, and we must understand the impact and abilities of powerful actors such as your own government, and -- as Mark Klein showed -- at times we must make difficult decisions with consideration of the political impact above that of your job security. Because even if we don't ourselves run the cables between different jurisdictions, the physical aspects of the internet remain an ever present factor in our work. We'll pick up the ethical dilemmas we may encounter in our line of work in future videos, and in our next segment we'll look a bit more at network ownership and how we can see the political structure of the physical internet. Until then, please make sure to check out the various links included in the slides, read up on the various internet outages, and perhaps research some of the other major, disruptive events on the internet. I'm sure you'll find a lot of interesting information that perhaps so far you hadn't considered in much detail, and perhaps you begin to see the internet as more tangible, physical thing. Thanks for watching - see you next time. Cheers!