Google IT Cert – Week 4 – Networking

Week 4 of the Google IT Support Professional Certification course on Coursera is the networking module. Presumably this is just an intro to networking, but I can’t see the second six-week block of classes until passing the first block. There has to be more.

Coming into this week I do know a little about networking, in a broad sense. I know there is something called the OSI model, which is a way of conceptualizing network communications. I know a NIC is a “network interface card,” and I know that everyone hates their ISP.

The OSI model of network communication
By Dino.korah [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)%5D, via Wikimedia Commons

Off the top of my head I remember that there are 7 layers in the OSI model. This is the standard we use to discuss network transport and the necessary “overhead,” that is, all the information needed to route the information we are actually trying to send. There are packets in there, being sent someplace, using all these layers of information to get where they are supposed to go. The OSI model shows how a network of devices will communicate using standardized protocols–the only way any of this is possible.

Networking is a fundamental part of our lives. This is especially true if you are going to be working with computers and networked devices. Think about it.

Okay, let’s go network.

In the first video, we meet a young guy who likes IT and explains that the internet is important. He seems pleasant enough. He explains that this internet is a bunch of computers connected together. This is called a “network.” Lots of networks can be connected to each other, and this is the internet, the “physical connection of the computers and wires around the world.” This is often misconstrued as–or spoken-of incorrectly as the world wide web. The web is actually the information on the internet. Email, chat, and filesharing are other ways to access the internet, in addition to the web.

Networking is a “super-important” field in IT, the designing, building, and management of computer networks.

Your computer is a client, which connects to a network run by an ISP (internet service provider) that allows you to connect to servers that host the web pages you use.

Computers have identifiers called IP addresses, such as 172.217.6.46. Networked devices also have something called a MAC address, which is a unique, usually hard-coded identifier built into the device. In order for a device to be networked it must have an IP address and a MAC address. This is all so stuff gets where its goin’.

Data that is sent over a network is sent in “packets.” These are discrete blocks of information that move as a unit over the network. A photo may have a million ones and zeroes used to encode it, but when you email it off someplace your computer breaks it up into, say, one thousand packets with one thousand ones and zeroes in each. This is a crude example, and probably not accurate.

You don’t just send a request to Google when you need to look something up. Your computer queries other computers that are “closer” to google.com, until one is reached that can directly communicate with a server at google. These computers know to pass along your request because every packet has the IP address of the sender and the recipient. Then, once a google server has your request, it will send a response giving you access to the website. This is a crude explanation.

Networking hardware includes:

  • Ethernet cable: This kind of looks like an old-timey telephone cable, consists of copper wires, and connects directly to your NIC or motherboard.
  • Wireless Card: This is a radio signal/antenna system that allows communication through the air.
  • Fiber Optic Cable: This is the fastest networking connection. It uses pulses of light transmitted over glass fibers to move data. That is awesome.
  • Router: This is the “first” device your computer connects to. It connects many devices together and “routes” the traffic over the network. The router uses a set of rules to determine where data is sent.
  • Switches: A switch is like a “mailroom,” if the router is like the postal service. Not sure this is a great explanation.
  • Hub: a hub does not perform routing, but sends all data to everyone.
  • Network Stack: “A set of hardware that provides the infrastructure for a computer.” All the components that make up a network.

The Language of the Internet

Network Protocols are the rules that determine how traffic is routed, ensuring that packets are routed efficiently, securely, are not corrupted, go to the right machine, and are named appropriately. TCP/IP are the foundational rules of modern networking–Transmission Control Protocal/Internet Protocol. IP is responsible for delivering packets to the right computers. TCP is used to maintain reliable transmission from one network to another. This is really important, too!

The “web” is how most people interact with the internet. It is made up of “pages” (organized into “sites”) that are basically text documents viewed by browsers. Pages are found by entering the URL (uniform resource locator) into the browser. For example, typing “www.wrongtree.info” into your browser means “on the world wide web there is a domain called ‘wrongtree.info’ and I would like to view it.” The domain (wrongtree) is a unique name and is registered by ICANN (Internet Corporation for Assigned Names and Numbers).

DNS (Domain Name System) is the process that allows you to type in words like “google.com” to your browser which then translates that into IP addresses which can be used by the computer. Your computer doesn’t know what “google.com” is, but it does know what to do with 172.217.6.46. DNS allows you use the internet without memorizing IP addresses, which is a luxury we didn’t have when I was your age.

Next, we switch presenters to some other clean-cut Google guy, who is here to give us a little history of the internet. He goes through his version of the “I like computers and was also a child who liked computers and now I work at Google” speech, at the end of which he informs me that even if I’m not a great test-taking student I can still make it in IT with a little “preserverence.” Great.

Computers used to be huge, they were slow, the government started DARPA which invested in computer research and built ARPANET. These were rudimentary computer networks, mostly between university computers, I believe. Then, in the 1970s, Vint Cerf and Bob something invented TCP/IP which is still the foundation of computer networking. Sometime in the early 1990s or so Tim Berners-Lee invented the world wide web. That was awesome.

Because the internet and its technologies are so old, there are some inherent limitations to it that affect us today.

IPv4 (Internet Protocol Version 4) consists of 32 bits in four groups: 10.10.10.10 which means that there are only 4 billion+/- usable IP addresses. We basically ran out of IP addresses a long time ago, so there is now IPv6, which consist of 128 bits, or 4 times more than IPv4. An example of an IPv6 address could be 385f:4e7d:4126:2220:6123:8721. That gives us 2^128 IPv6 addresses, which is a number so large the presenter has a very clumsy and painfully vague explanation involving grains of sand. Let’s just say it is enough so that everyone can have like, two phones and a laptop and still have trillions of addresses left over.

In addition to IPv6, NAT (Network Address Translation) allows an organization to have one public IP address and multiple private addresses withing that network.

This week’s discussion is about imagining a world with a fixed number of IP addresses. Obviously this has been overcome in the real world, but a scenario is easy to imagine:

Every system has limitations of some kind. That will always be true. Imagining a world where the internet has limited "real estate" is not that difficult if you imagine a world that has actual real estate, such as the actual world we live in. 
If there were always to be a finite number of IP addresses, I suspect you would see a very competitive market develop for trading those addresses. Naturally, large corporations and the rich would dominate, and the commoners would be left with whatever scraps the scale and the scope of the market had left over. 
It is not hard to imagine a world where only the rich and large corporations had the resources necessary to acquire and maintain internet-connected devices. 

I have to say, I am also ready to imagine a world where the chat forum discussion-as-a-class format leaves something to be desired. But I murdered the 6 question quiz, so, great.

Now we come to a rather amusing video about the impact of the internet. I feel like I should warn the credulous student that listening to some dude from Google explain what globalization is in ten seconds is possibly giving you an incomplete explanation of the subject. I know this is an IT training course, not a geopolitics or economics course, but please don’t take too seriously what this enormous, tax-evading, data-collecting marketing-by-surveillance monolith says about globalization. The point, apparently, is that the only constant in tech is change.

Which brings us to a reading on the Internet of Things. IoT is one of the most common themes in tech news today, along with blockchain technology and, oh, probably Facebook, for some reason.

About the reading, I kind of already know what IoT is, and why it is an important subject for technology workers and consumers. I do usually like Wired magazine–maybe it is the consumer-level explanations–and recommend it for anyone casually interested in learning about technology in a broad, consumer-level way. I am interested in learning much more about security, and the proliferation of IoT devices will add to the already disturbing amount of breaches, vulnerabilities, exploits, and hacks that happen with IoT devices. Think twice about buying that internet-connected piece of crap that does not need to be internet-connected. Do we really want giant corporations listening to us in our homes and using the data they collect to sell more crap back to us? Yeah, some of us do, I guess. I don’t, but, on its face, a button in my house that mails me snacks is not the worst idea I’ve ever heard.

That brings us to the last video in this module and it is a tight 3 minutes about privacy and security. Personal data, spending habits, copyright, etc., etc., all are on the internet. I assume there is a lot more to this course regarding security because this video kind of only says that security is an issue. Believe me, I know, I read an article in Wired.

And then there’s the quiz. I got one question wrong because I was not thinking it through. It asked if a series of IP addresses were valid and I said that they all were, including one that had 345 in it. This value is more than 255, therefore it is not a valid IP address. Only values of 0 to 255 are valid. This is important to remember, even if you know it already. Another lesson, read the question carefully.

Onward to week 5 – Software!


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