 All right. Welcome back to Computer Science E1. My name is David Malin. This is lecture four, the internet. So we have talked briefly, and you've been inundated perhaps on the website with links to podcast this and podcast that. But we're at the point now where on the agenda is to discuss such things as podcasts, which begs the question, what is this podcast that we've been touting? Anyone at all? Great. Putting it to good use already, I see. Podcasting. All right. Would I help if I reminded you that with problem set one submission comes an opportunity to win this iPod shuffle and better yet, this iPod t-shirt, which we will distribute at some point over the next week or two once we've graded the problem sets? Anything. Podcast. Yes. OK, good. So it certainly refers to, in part, the ability to download audio content and video content in such a way that you can transfer it to something like an iPod shuffle or a video iPod, or if you're not even familiar with these things, just a little electronic device that's small enough these days to fit in your pocket, on your shoulder while jogging, and so forth. And perhaps podcasting is best explained by just a demonstration of precisely the term. So on E1's website, there's a link in the left-hand menu as well as via this John Harvard statue, if you haven't noticed, who's touting an iPod himself. If you go to that page, you will see just a typical web page in the same style as the rest of the website, but with links to all of this so-called podcasting content. Well, to be clear, the idea of a podcast is not to download the information necessarily through a web page. Otherwise, this is just a web page. There's really no need to call it podcasting. But really, if you look at this same content, for instance, through the view of what's called a podcasting client like iTunes, you'll begin to get a better sense of what this hype is all about. So in fact, if we follow the link on E1's website called subscribe to the feed directly through iTunes, assuming you have iTunes on your computer, you'll see a web page like this, which I brought up briefly in a previous lecture. And essentially, this just shows you exactly the same content. What is this content? Well, as you can sort of see from the small text there, we've been posting, as you probably know, videos of these lectures, audio files in the form of MP3s of these lectures, as well as the TF's fantastic work on these new series, The Videos of the Week, a couple of which we showed two lectures ago. So what then is a podcast? Well, at the end of the day, it's sort of just a new buzz phrase around a very basic idea that's long been possible on the internet, the distribution of audio, video, and other kinds of content. But it's done technologically in a way that's somewhat new. Specifically, even though you're seeing all of these videos and videos of the week via iTunes, none of that content currently is actually hosted by Apple. None of it is actually hosted by iTunes itself. This is in contrast, for instance, with a lot of the music you buy from iTunes, which presumably is hosted in some sense by Apple itself. Rather, what we did at the start of the year was signed up for an account with Apple for iTunes. They approved us because they do a manual process still these days to sort of moderate the kinds of content that's posted. And what we simply maintain in E1's website is what's called RSS, really simple syndication. There's other expansions of that acronym. But in short, it is literally just a text file, a text file with a lot of phrases and sentences that describe what is in this so-called podcast. Because at the end of the day, a podcast is just a feed, if you will, of video files and audio files and PDFs, for instance. And we'll actually spend more time in our multimedia lecture on what exactly we mean by MPEG 3s and MPEG 4s and QuickTime movies. But for now, just take it on faith that these are just videos, just audio files. So what we do every week is when we release a new lecture or a new volume of videos of the week, we simply edit this text file with a simple text editor, Microsoft Word or something much simpler, in fact. And all we do, for instance, to say that we have just released the video for lecture two is the following. We type up this short paragraph. But you'll notice, if you glance closely, even though the text is a little small, that notice that next to a lot of these words are these angled brackets, open bracket, something closed bracket. And those are examples of XML elements or tags. And in fact, what you're seeing now is a glimpse, a sneak preview, of what you yourself will be typing in just a few weeks time when we get to the website development aspect of the course. You yourselves will be developing websites, not in XML per se, but in a derivative called xHTML, or perhaps the more familiar term HTML, which is the language in which web pages are written. So long story short, every week we update this file. We say what the lecture is called. We give it a bit of a description. We say who gave the lecture, how long the lecture is. And most importantly, we tell iTunes and really anyone else that wants to look at this file where the movie file is. And what I've highlighted there is just a URL, http, colon slash slash, www.fas.harvard.edu, and so forth. So really what a podcast is, from one perspective, is just a big RSS file, an XML file that describes what's in the podcast and where you can actually go to download the actual content. So when you actually pull up a site like iTunes or a whole bunch of other programs or so-called podcast directories, all you're seeing is one company or one individual's presentation of that material. And if I double click on one of the links provided in iTunes, I'm not downloading the video from iTunes per se, but rather iTunes is directing my computer to where the actual content is so that it can be copied to my local computer and then subsequently played or transferred to my iPod or equivalent device. Well, E1's podcast is now in its second year. And last year, we would not perhaps have had some of the success that we did, not only with our own local students, but also with reaching other non-potential students via the internet. We received a good amount of attention from a gentleman that you are about to meet. Victor Cajillo is the host of a podcast called the Typical PC User Podcast. And we'll post a link on the lecture's page after tonight to his own podcast, but this was a gentleman that sought us out after E1 was cited in a number of blogs and news articles for having been among the first courses, at least within Harvard University, to provide students with access to its content via podcast. Victor, given that he does a weekly show about all things related to technology, took an interest in us and was kind enough to invite us onto his radio show for series of interviews and so forth. And so what we've done is invited here tonight to speak for just a few minutes about what it is, what it takes for a typical person, if you will, someone like Victor, someone like yourselves to actually get a podcast of his or her own up and running. And to be clear, a podcast does not need to contain video content. It does not need to contain PDFs. In fact, at the very beginning, if you will, podcasts were really just internet-based radio shows. But they were radio shows that you didn't really tune into live, but rather someone in their studio or their basement or their living room would record a radio show of sorts using a nice microphone, headset, and so forth, maybe playing music and so forth. They would save that recording as an MP3, just a computerized audio file. They would post it via their own RSS feed so that other people on the internet could download that audio file. So it's a radio show in spirit, but at the end of the day, you're not listening to these things live. You're downloading them and listening to them sort of a la tivo, but for radio and for other video content. So with that said, I thought a fun introduction to tonight's lecture on the internet would be to make use of precisely this technological tool of the internet. And one of the up-and-coming trends, certainly, is this use of not only listening to audio and watching video, but delivering video and delivering audio. So what I've pulled up here in this small window is a program called Skype. How many of you have ever used Skype before? Anyone? So two, three people. So what is Skype? What is this little thing I've pulled up here? OK, so it's pretty much a telephone in your computer. It's several things, and that is certainly one of them. One, just to be most familiar perhaps to the audience, it's a program with which you can instant message other people. But that's really just an afterthought with this program because the crux of Skype, the real value out of it, the real feature is that it does a very good job of allowing you to conduct voice over IP or VOIP, if you've heard the buzz phrase. And this essentially, as you've said, is just the ability to make phone calls via the internet. What do you need to do that? Well, you need an internet connection, obviously, and dial up doesn't really work so well these days for something like this, which is fairly bit intensive, but rather something like DSL or cable modems are wonderfully suited to this kind of technology. So in a moment, I'm going to click this big, glaring green button, which is going to dial up Victor, who's sitting in his own office far away. He's going to connect with his own copy of Skype and using this freely available Skype software. This is going to cost us 0 cents a minute. We're going to have an audio phone call with each other. And in fact, though my camera won't be turned on, since it's not so interesting to see me up here yet again, Victor's camera will be on. So you'll actually see this gentleman himself. The video quality tends never to be as good as the audio, but the wonderful thing, again, about Skype is that, and even I've used this, it's free. And if only for the audio-based phone calls, I've spoken with friends of mine in other countries for free. And even with a decent internet connection, it sounds just as good, if not better, sometimes than telephones. But it certainly depends on your connection. And I will say, we're going to use this 50-cent microphone here tonight, since, and this will actually probably suffice, we're going to use the speakers built into the lecture hall. But typically, and the only downside to using software like this is that, one, you need a microphone, and you need speakers. At least you have the latter usually with your computer. But the problem, at least for Neophytes, when it comes to using this sort of stuff, you have a desktop computer that has usually two speakers sitting right here. And you have a microphone, however, cheaper, expensive. If you keep that microphone too close to the speakers, what's going to happen? You're going to get really annoying feedback, or that really high-pitched screech, if it's even close enough. And that's the only logistical issue to work out that can at least initially be sort of enough of an impediment to even bother with the technology. But for 10, 20, or more bucks, you can actually get little headsets, which if you're embarrassed to wear them on the street, you can at least wear them in the privacy of your own home. And that gives you really high-quality audio back and forth. So with that said, let's dial up Victor and ask him just what it takes for someone like him or someone like you to go about presenting your own podcast. Hi, Victor. Can you hear me? Yeah, I am well. Good to see you. This is working well, it seems. I've just put up your video when we have your audio going through the lecture hall here. Well, hello, everyone, nice to meet you. Well, Victor, I've given a quick introduction. But one question first, where are you geographically right now? I'm located in beautiful Southern California. Will this still work? Fantastic. This is actually a really good connection. So if you would, why don't you tell us a bit about your experience podcasting, what it would take for folks like these to get up and going with their own podcast? And then if you don't mind, I can try to relay a couple of questions if they come up. Yeah, if you happen to do that, thanks for inviting me. So it's all about content first, you guys. Podcasting is one of those scenarios in new media. That means that you and I have a voice, and we can let people know about what we're passionate about. Whether it's journalism, non-comparative music, comedy, couple cast, or just computers, like in my case, there is no formula today for creating a successful podcast. It's about all of us telling our stories. So the first thing you need is good content and a good story to tell. Once you have that, the rest of it is just simple technology. So let's talk about what that looks like. You're gonna need some kind of a platform to record your podcast, primarily your computer. You can start with something simple like this headset mic. You can buy one of these for $10 to $20. And you can use something like that to record your audio onto the microphone, or even a USB type mic like this sounds in here, which is like $80, which you can play directly into a PC or a Mac. So that's the first thing, a microphone. Maybe you need some kind of a sound card, and most of our computers today have a sound card, so that makes it very easy. Now you need a way to record the sound onto your computer. If you have a Macintosh, GarageBand has built-in capabilities to record your voice so you're all set. But no matter what platform you have, one of the most favorite applications for podcast users is called Adacity. And it is an open-source cross-platform application that lets you mix together the sound of your voice, some music, some sound effects, and then combine all those into a podcast as an MP3 format file. So if you record your voice, you mix those elements, you save the file as a MP3, and now you have your content ready to put somewhere for people to listen to. This then raises to kind of the next step of it is how do you get your information from your hands or your computer out into the internet? And the way that you do that is that you need to get yourself a hosting provider or a blog provider. So just like in blogging, where you're writing down your journals or your news stories and so on, there are providers that are getting podcasts. There's now the ability to save those MP3 files and upload them to their servers as well as to place for you to put your show notes and they will provide you with those services for no money. For example, switchpod.com, posting your files and people telling people where you need to go get them. They did care about all for you. You don't have to worry about running out of bandwidth because too many people have heard of your show. So it was a big problem at first because people didn't have enough bandwidth. People like Lipsen and switchpod have come to the rescue for very little money. So now we have our contact. We have our place that we have put that content and now we need to publish the show, put it out on the internet so that people can go to a URL and they can either listen to it right through the website or they can download it by using a podcatcher. I don't know if David talked to you about those, but programs like iTunes or like Juice that let you go and they look at that RSS feed, they say, oh, Victor has a new show up there. I'm subscribed to it. Go down and grab that show from that server. And so now once you have posted that podcast and get it available to the world, now it's up to you to do what I call the last part of podcasting, which is promoting your podcast. And this is an area where you're getting a lot of different opinions. At first I would say promote it with your friends and family. After all, they are the kindness to us and they'll let us know what you're doing well and in case a lot of us get used to being behind a microphone or not media professional, the media you can talk from, the newsrooms of America, we're just people that are talking. Some people do their podcasts live, stream of consciousness and don't do any editing. Other people like me do editing and add music and sound effects and things that give it a more polished preference. But it is purely your preference that way. So I would let your family members with your friends know about it first, give them the URL, help them listen to it, make sure that you can download it and then, if only then, should you really go out and promote your podcast to the world. And the way that you do that is that you let podcasting directories know you're there. I'm gonna give you three major ones so they'll have literally hygrids. The iTunes Music Store, which we're all probably familiar with, they'll be happy to review your content. You give them the name of your show and where the RSS feed is located and they simply go and review that and unless the content is questionable, you're usually in their directory within about a week and they can tell your friends to look for you and your show with the iTunes. There are also podcastsally.com and podcastspickle.com. Those are two of the biggest directories and those are places where you and I as listeners can go and look for podcasts on all kinds of content and believe me, there's a lot of content. Matter of fact, there are not one but two different podcasting are curling and are knitting. So you can imagine that anything you wanna look for is out there. So once you have your show, if you put it in those directories and people will find you. Now, if you're looking for to be a star and get rich on podcasting, this is probably not the time you'll be the one for those. I think I've heard that more than, less than 10% of all podcasts have more than 100 people listening or subscribed to the podcast. So it is one of those medians that is described without a long tail of an arm which says that there are lots of people listening but there may only be a very few listening to your specific type of show because of their preferences. So do it for the passion, do it because you wanna get the message out. In my case, my shows deal with the typical PC user podcast teaches people how to use PCs. Typical Mac users for people like me just switched to a Mac year ago so I'm learning a lot from teaching and then my other podcast is called Immigration Tales where I tell people still worries about immigrating from one country to another. Those are all about passion for me. Yes, I have a few listeners in some of them but I only have them because I put a product out that I'm passionate about and even if I have 100 listeners, I will still do it. So it really becomes at the end of the day creating your content, publishing your podcasts and show notes, promoting your content, and then wrenching the P. Maybe they don't want to go too quickly but I think that's the whole lineup. No, not at all, that was fantastic. Would you mind fielding any questions if some hands go up here? I'd be happy to. All right, so I'll be the one to stand here awkwardly and look for the hands. Yes. Thank you, Victor. What do you see as the future of video podcasting is the question? Ah, well, that is a huge future. Now, the thing with video is and there are some wonderful examples of video podcasting like now is that the complexity is quite a bit more, okay? There are a lot of fun to watch and ask the ninjas out there and you have other shows that are out there rockin' for example. But the editing process and the time that it takes to make those is a lot, it's a lot deeper curve. So I see that there will be those that will look more like traditional media but I don't see it being as heavily geared towards people like you and me who combine a $10 microphone and get our message out and that's what new media to me is about. Thank you. Other questions from the audience? Yeah. As someone new to podcasting it doesn't seem like you could put a podcast out and get a large audience or get even really a significant audience right off. Is there really a huge demand out there from podcasts of all kinds? So as someone starting off his or her own podcast for the first time is there really demand out there for say one lone individual's podcast or for these podcasts in general? Well, demand is a pretty podcasting. You'd be surprised. There are some shows that take off for unknown reasons. There's a wonderful couple of shows for example called Keith and the Girl and they are kind of R rated but they got on the New York before you knew it they had a massive audience and now they do. So as a new podcast for what you need to do is get yourself into the podcasting community from within. If you listen to podcasts send them out an email and say hey I have this new show about photography would you mind playing a promo from my show on your show that I have a lot of people and so from the inside we kind of get to know each other we go into forums and into all of your forums and the podcasting community kind of organically grows. If you have good content people will come to the show. One more question. Is there a possibility for podcasting generating income in the future? Well, I should hope so. Let me tell you I think that there is people are generating income in podcast today there are plenty of podcasts out there today that have 8 to 9 million downloads a month and that are starting to generate some dollars but I think for the majority of people that is the great unanswered question of podcasting how do we turn the podcasting model and marry it with a more traditional media advertising model in a way where some people will make money and most people will be okay with maybe just paying for their hosting costs every month that 10 to 30 dollars a month so right now that's the big question in podcasting and I'll look into that in the future. Well Victor, thanks so much for joining us today we'll be sure to post some links to your podcast on the course's website after tonight. It's been my pleasure and I'll thank you for having me. Take care, thanks. Bye bye. Only because we have the window up now and this might be somewhat anticlimactic rather than having audio and video up there but one of the neat things you can do with Skype as well today is if you pull up this little button here you'll see something quite similar to a telephone keypad and in fact, let's see am I allowed to type in this number or should I use a different one? That's okay? Okay. If we go ahead and type, how do I, oh wait can I do this call? Oh no, our, okay so as of a few weeks ago you were able to do this completely for free and you were able to call landline phones using Skype and I was doing this briefly or at least a friend of mine was doing this briefly and calling me all of the time from Skype because it was entirely free and he was in California thus avoiding the long distance. I do realize now and remember that they've turned back on the feature. It's still incredibly cheap and in fact I used Skype to talk with friends when I was in Argentina for a week because it was pennies per minute as opposed to dollars per minute using an actual landline phone and again you certainly have to contend sometimes with quality issues and you wanna have a decent enough setup so that you're not getting feedback but it certainly is a wonderful alternative and the upside of Skype now charging us is that I will not reveal Ray's personal cell phone number to everyone on the podcast but know that that is an option and that's one of the ways that Skype aspires to make some money and also Leo in part answered to your question about making money off of these things we can perhaps those inspiring entrepreneurs among you take some comfort in that you can even start a huge video focused business that doesn't make money e.g. YouTube and still sell yourselves to the tune of $1.6 billion as of this past week. No, that's quite true and just to summarize I mean there have long been a number of services and especially these days ever since the dot com era where you get the same idea the same technology has been around for years but all of a sudden for whatever reason you start to get critical mass around some product or around some website and there's just huge valuations put on these things YouTube being an example of one of them and long story short, if you're not familiar YouTube is just a video sharing website you sign up for a free account you upload your own personal videos that maybe you took with your little digital camera or shot with your regular camcorder and then digitized and it's really just to share videos with people and it's become incredibly popular and Google for one sees upwards of $1.6 billion value in this I will say to play the other side of the coin and devil's advocate if you will I think only time will tell if a lot of these ideas and a lot of these technologies and a lot of the sites are worth the valuations that are being put on them and one might argue that even what's happening in the past couple of years with a lot of the prices that are being tacked onto MySpace and YouTube and Facebook and so forth it almost makes me wonder sometimes if people have already forgotten the lessons of 1999, 2000 and so when it seems like there was similar money being thrown around but even then time will tell that is a perfect segue to a video that Dan brought to our attention you will recall a couple weeks ago we passed around a hard drive both one closed and one open and we showed our own animation of what goes on inside of a hard drive what Dan found on YouTube and if you're wondering what YouTube is this is YouTube so this is just a site where you're able to share and watch and play videos this is a video that someone made rather delicately by taking the lid off of their hard drive but a working hard drive that was still physically connected to a computer they just physically removed it from the box but they left the ribbon cable connected and you'll see what exactly is going on inside of a hard drive when it is actually running in your computer it's just a minute or so long here here we go let's see if I can make it a little bigger for us have you ever wondered what that sound is or that sound this is why they have lids they very quickly become an interesting but you see what's going on inside the drive but that was sort of a lot of activity and a lot of noise for deleting a folder what do you think explains the relative length of that process of deleting a folder that would seem to be a pretty atomic operation okay perhaps finding the folder seeking to the folder it looked like the reading head was doing a lot of back and forth though which would almost suggest that it didn't find the folder but it probably did why else than might have been toggling back and forth so much there could have been information on different parts of the disk the folder itself might have been fragmented in an implementation sense folders themselves don't really require a lot of storage space because they can be represented rather efficiently but what sometimes is inside of folders easy question yeah so in this case and as the gentleman i think explains in the comments accompanying this video there are actually a whole lot of files in that folder which explained for whatever operating system he was using that it was recursively going through and deleting those files and maybe other folders as well so we'll put a link to this on the course's website as well if you'd like to take a look or at youtube in general uh... and it's worth noting too just to tie in our first two discussions of hardware with tonight the internet and also to play off of some of the things victor said in addition to this podcast being available to students by itunes it's available to really anyone with itunes uh... at least some of the lecture content in this year the videos of the week content what that's teaching staff and i spent last week struggling with was the load that was apparently being placed on this podcast this year uh... based on our these answers tonight to what is a podcast in the deafening silence that accompanied it i can only hypothesize that it was other people who were downloading the podcast this past week but long story short uh... thanks to those individuals who subscribe really thank you uh... we crippled one of the extension school servers early last week such that i got a nice email effectively explaining that we've been booted from the server that all other courses use at the extension school so that way induced the last minute scramble we then contracted with a and outside third-party host uh... company called dream host that you will see later in the semester because we'll use them for you the students when you develop your own personal websites with your own personal domain name but at dream host we have signed up for a relatively inexpensive plan they gave us plenty of disk space it's you know a few tens of gigabytes maybe a hundred or more gigabytes but storage problems are not what we have but it did offer us one point six terabytes of transfer or a bandwidth that is to say we were allowed according to this plan over the course of a month thirty days this is what our contract allowed to have people on the internet wherever they are download up to one point six terabytes of information and none of our e one videos are nearly that huge the biggest files maybe two hundred fifty megabytes well what's one order of magnitude larger than a gigabyte damn a megabyte is a gigabyte well what comes after gigabyte terabytes so terra essentially denotes what numeric value trillion so you're familiar with megabytes in terms of floppy desk one point four exactly what we did the first lecture two one point four megabytes you're familiar with uh... heart drives that you have which have twenty maybe four hundred gigabytes imagine now having access then or the ability to let people on the internet download one point six terabytes of information over one thousand gigabytes of information well we got a nice note from dream host uh... four days into our contract explaining that in the first four of thirty days of the month we had used one point four of our one point six terabytes and just like the cell phone companies today do they'll charge you if you go with every gigabyte over uh... and you know if you've ever gotten a three hundred dollars cell phone bill that the overage cost tend to be high so i passed along to the extension score estimated bill of six thousand dollars for the first month of our free podcast that we don't charge for mind you uh... so we quickly up the plan to a four terabyte plan uh... now an eight terabyte plan should hold us over uh... but again thank you all of you for tuning in remotely it's been a wonderful challenge this is honestly the first semester in eleven terms of teaching this class that i think we've even spent more than a split second even using the term terabyte and it's sort of a fascinating thing just technologically these days to now be getting into these kinds of numbers so it's only a geek and perhaps really take pleasure in that idea but uh... it's amazing what's happening and it is ideas and technologies and websites like youtube that are really driving some of this growth in data storage requirements i mean a typical video that's uploaded for you want is between twenty five and two hundred fifty megabytes contrast that with one mp3 of a song that for instance you might have downloaded back in the day from napster or these days from itunes itself three megabytes four megabytes so when you start talking about distributing two hundred megabyte video files you start to deal with a lot of interesting server side issues and that's precisely what we coped with this past week so more on those kinds of things in the future for now let's dive into the topic that we've skirted over up until now which is quite simply well the internet what is it alternate over to you since my first question of the night one over so well what is the internet but you'll see that the slides in this class because we have notes and because i like things to save rather dynamic and not follow a script i mean slides can't really get fluffier than this right a guy surfing the internet so we'll use this for ten or so minutes when we talk about the internet what is the internet it's a series of tubes it's not a truck and none of you are familiar with the quote that uh... senator watch john steward and it comes up every other night so watch john steward in that little joke will make sense so what is the internet for real so it's a large infrastructure of servers and routers and just really computers that are interconnected somehow all over the world is the network of networks and even if you're not particularly the technophile and are still taking this class you probably have an idea already that a network is simply a bunch of computers connected together well how that's done and what kinds of technologies you can use to connect those computers together will be one of the foci for tonight as well as next week's lecture but today we focus more on mostly the higher level details what is the internet what can you do with the internet and in our continuation of this lecture next week will dive down deeper and look underneath the hood so to speak at how it all actually works on a more tech technological level but let's for tonight first start off with a couple of softballs so what is a domain you've probably heard this term but give me a definition for it in layman's terms what's a domain yes so it's an address of sorts right like you've probably said out loud cnn dot com before or harvard dot edu before well that's just a domain it is sort of an english-like phrase that describes some kind of network of computers and a network of computers that's usually geographically related right it's pretty reasonable to assume that all of the computers related to harvard dot edu are kind of sort of in the same area though that doesn't need to be the case technologically well let's actually take a step back then because if we're already getting ahead of ourselves if we're already talking about the internet before talking about it's basic building blocks well this is easy right we talked about this in our first couple of lectures here is a computer you can tell even the course becomes dated when computers don't really look even like that anymore right and that's kind of sad but this is a monitor from yesteryear on top of a desktop from yesteryear i'm not very good with drawing lcd so stick with this version add two computers to the picture connect them somehow with some kind of wire who cares what what do you got you've got a network this kind of network might simply be called appear to appear network well why will you might guess because you have two peers to equivalent types of computers somehow communicating with each other appear to appear network can also involve many many other computers napster and its infrastructure was in a sense of peer to peer network because all of these peers all of these individual consumer pcs were eventually connected to one another albeit through a central server so that was peer to peer in a sense but software today that's particularly used for file sharing or more peer to peer in this sort of sense and i'm not going to draw hundreds of computers on the board here but if you can imagine a network of a whole bunch of computers really arranged in an ad hoc fashion where some computers might have direct connections with one another some can only talk to other computers through other computers that's a peer to peer network as it's usually understood today it's sort of an ad hoc network that's formed using various types of internet connections and though i draw them with lines here i don't mean that these two computers are physically connected i just mean that they have some kind of internet based connection they could be in completely different states or countries the lines just represent software type connections network connections well with that said let's actually go to a more common scenario at least it's consistent with the types of networks you use each day if i all of a sudden and just for the sake of dramatization draw one of these computers as relatively bigger just because it's stronger more powerful it's got more ram it's got a better cpu i'm gonna call this thing in this context a server and meanwhile i'm gonna call the thing on the left what uh... cpu but in this context you might have heard the phrase of the word land would describe the whole thing we'll come back to that in a second but what i'm looking for is the relationship between this server and what might be called a client computer so if you ever heard the phrase a client server relationship or really just hear these words tossed around a server a client it's pretty much just like what happens in a restaurant you sort of have one guy who's running the show the waiter the server he will answer your requests or will provide you with information or really food that you the client asked for and this is terribly representative of how most internet based applications work today for instance you sit down at your computer and you pull up internet explorer and you type in cnn dot com you in that context are acting is what's called and you're making some kind of request over the internet will expose the inner workings next week cnn dot com which is obviously the server in this case cnn dot com server or servers looks at whatever request you've sent and that request is going to be along the lines of give me your main page your home page the server is going to grab that home page or generate it and then reply just as you've received your dish at the restaurant and it's precisely that relationship sort of a subservient relationship with the client asks the server for something and get something that sort of captures in fact what we were doing with skype just now albeit only one side of it when we dialed up victor the way that skype and programs like it tend to work is clearly there's a server in the middle because even i personally had no idea where in the u.s. at the moment victor was apparently he was in california well if i wanted to make a direct connection like a peer to peer connection to his computer let's sort of a chicken and the egg problem how do i contact victor if i don't know where i should contact him and so that's why a lot of technologies a lot of websites a lot of software products use central servers so in effect what happened when i double-clicked on skype on my computer well my version of skype made a connection to the server and it wasn't just this one time request response it rather is a persistent connection like calling up skype's main server on the phone and just maintaining an open connection technologies different but the spirit is the same meanwhile guess what happened over well if this is victor's client it too made some kind of connection to skype server skype now knows where david is skype now knows where victor is and skype server can effectively put us to in contact with one another how many of you use a well instant messenger pretty much the same exact design for that right when you sign on to a well instant messenger you're running a little client on your computer it connects to a i m's main server which is called i think oscar dot a well dot com is the host name the address they use for it something like that and then your friends connect to a i m server as well and then all of you can instant message each other because you're all using a well instant messenger server intermediary now this sort of implies what about the privacy of your instant messages not very right literally all of your instant messages for the most part go through a well instant messengers and a well's main servers which certainly means they can do what with them if they so chose read them certainly store them in perpetuity certainly it's really up to them whether they do this i don't know but this is certainly an issue when it comes to say uh... current proposed legislation which i think we touched upon briefly in lecture one or two were i s p's which are not a well instant messenger per se but your i s p's can certainly look at all of the emails and all of the web pages that you're accessing from your computer right after all who who do you use to connect to the internet these days comcast so if your computer in that sense is the client and you're using comcast servers to access the internet well that's just that they in that case are the intermediary between you and everyone on the internet now for the most part i s p's don't retain data they don't retain data on what websites you visited and what emails you've sent or the content at least of them just because that sort of more legal trouble than it's worth if they're not required it just cost money to store this data and what do they really needed for they maintain logs of that you sent an email likely and maybe who it was to but usually not the content but if you pay attention to current media goings on one of the proposals from at least this country's government is that they want to keep around information for at least three months six months and this is a huge deal for the i s p's and others because it's just expensive if nothing else and remind all the civil liberties issues that it might raise but that said back to technology these two basic relationships either a client server relationship or sort of a tiered model where you have multiple clients connecting to a central server now consider what victor and i and when we were doing we were transmitting not only audio but video as well and what do we already know from our brief chat about podcasting that's implied by the distribution of video in general sort of a leading question but which let's all make it more frank which is which costs more in terms of space to send a little a well instant message like a smiley face or to send your smiley face over the internet it's a your smiley face in the form of a video so if all of a sudden these very popular services like skype and a well instant messenger are usually using these centralized server models you would think this quickly becomes problematic especially for video right consider the issue of our podcast we had one central server originally at the extension school and it was just serving content to clients it was not even serving as an intermediary to other clients will now imagine skype do you think that skype routes all of our audio and all of our video content through skype server does a well instant messenger do that when you can do a direct connection quote unquote and send someone a really big file or really big image on theory no and ideally no because what the server simply does as i sort of suggested in the voice over is it informs this client and in this client how they can directly contact each other and thereby circumvent the intermediary because once the servers put those two clients in touch what do you really need him for after that now that's a slight simplification because that is actually problematic these days because how many of you with your dsl or cable modem connections have home routers or firewalls if you know what that how many of you have not only your modem plugged into your cable line but also a black or blue box that lets you share your internet connection among multiple computers in your house well if you have one of those things more hands are going up and we'll come back to this either tonight or next week you are sharing your one your one pipe to the internet among multiple computers but the effect of that usually is to create the appearance that even though your home might have ten computers in it or three computers in it to the outside world it looks like there's just one of you because i comcast only presents you with will get back to this one i p address as it's called one means of addressing your computer this is a problem though because if skype knows where you're coming from and skype knows where victors coming from well suppose that victors on a network with a whole bunch of other people and suppose that i'm on a network with a whole bunch of other people in other words we might be sharing our internet connections purposes now realize or at least get a sense of the fact that the server can't necessarily put two people in touch with each other that are behind the so-called routers or firewalls for reasons we'll get back to but this is why if you've ever tried with msn messenger or aol instant messenger to do audio conferencing or do video conferencing it usually doesn't work those programs are not nearly as good as skype is and as say google talk is these days at using various tricks to get around those kinds of issues and we'll come back to that in more technical detail in a bit but if you've ever tried you can try tonight try to initiate a voice or video connection with someone with aol instant messenger or msn messenger if either of you are behind one of these home routers odds are it will not work as well as at least skype and google talk but more on that in a bit so you've got couple of computers connected via cables you've got now a let's do it this way you've got not just a server here but you've got a whole bunch of computers in your home as you were just saying and all of these guys want to connect to the internet it stands to reason that if you want to connect multiple computers together not just to you need to wire them not necessarily to each other but to some central and as soon as you start connecting multiple computers together using whatever kind of technology maybe you put all of these computers inside of a very oddly shaped building as suggested by this rectangle in the door well what do you then have you have now what was described earlier as a a land so from the beginning a computer you know what it is appear to peer network is just a two computers connected together a land is multiple computers connected together and they are usually very geographically proximal to one another so that's why i drew this very goofy looking building just to suggest that if you have a whole bunch of computers connected together in some very tight space like a building or maybe even a city block the general term for to describe that would be a land contrast this with something you might have heard more so perhaps in years past but a whan well what does land stand for local area network right this acronym pretty much explains what it is it's just a very somewhat vague term it doesn't have any minimum number of computers here that you have to have it doesn't have any maximum number of computers it's a general term you can whip out to describe a bunch of computers connected together that are sort of related to one another because they're in the same building or maybe because they're physically all connected to the same central device a whan by contrast wide area network it's just more than that you maybe you have a whan for argument's sake when you have a building here and then building here and you connect those buildings together via some kind of cable then you might say alright now that's a whan because it's spanning multiple lands so you have a computer you have a peer to peer network you have a land maybe have a whan what do you get when you connect all of these lands or whans together somehow or other a network yes but you get the network if you will you get the internet and that's why i introduced this as the internet being the network of networks you can take it one step further the internet is the network of networks of networks of networks it's sort of the uber network to which the entire world at least that with networks is interconnected these days so then what is a domain well domain is just a way of describing a land or a whan or a bunch of lands or whans there's really no hard and fast rules around any of these atop there i've put a domain of harvard dot edu well that is just the name given to describe all of the computers you know on harvard's campus at right there's a column called subdomains well sometimes if only for administrative simplicity it's nice to sort of organize your own network your own whan your own domain into hierarchies with different people perhaps administering different parts of the university or the company and so you have the ability on the internet to describe computers not only by their domain name but by subdomains for instance how many of you already have a fa s account okay so about half of you and if you don't already the current problem set uh... charges you with obtaining one where the previous one does if you have an email address of the form mail in at fa s dot harvard dot edu your domain name is generally called harvard dot edu and your subdomain is fa s that harvard dot edu how many of you have an email address in harvard dot edu okay so many of you as well so if you have that address how many of you have a at harvard dot edu address where your first name is something like not quite like this but capital david underscore capital mail in something like that well harvard does that in its domain name it'll give you david underscore mail in at harvard dot edu but most of you probably then have more local departmental accounts that david underscore mail in at harvard dot edu is just a so-called alias to and this is just one way that harvard administratively and technologically keeps things nice and separate for different people to administer what's another example of a website or an entity with subdomains anything come to mind anything at all about craigslist so in a sense you've seen something if you go to dot dot dot craigslist dot org what city's listings do you get san francisco's in fact which is their default website if you go to boss b o s dot craigslist dot org you get instead boston's listings but it turns out in that case the u s is something called a host name which looks sort of like a subdomain but it's a little different so let's let's take a look here if we let's take a look little bit more at the subdomains and we'll see where the technological relevance comes here's a whole bunch of suffixes many of which you're probably familiar with what looks immediately familiar on this list besides dot com dot gov dot edu dot net and then there's a bunch of others some of which do already exist some of which have been proposed to exist perhaps the latter one on the far right gets the most attention in the media these days but these are all what are called top level domains right so we did this little exercise in the board to sort of give us the bellistic building blocks of what a network is and what a network of networks is well the means by which you describe networks is by domain names part of which is the so-called top level domain in cnn dot com inferring from these mere descriptions alone what is the t l d or top level domain of cnn dot com dot what was it dot com dot com this is just a generic way a general way of saying that cnn's domain is generally speaking commercial if by contrast you visit dot dot dot white house dot gov what does its t l d imply again a sort of an easy question it's somehow government related and in fact until a couple years ago if uh... you ever made the mistake of visiting dot dot dot white house dot com at least one of us has been there uh... you would have seen a very different website than the one currently presented by the bush administration if you google around for i don't think it's still active but you'll perhaps find screenshot or actually if you're really curious you can probably go to uh... uh... search google search for i don't know why i'm promoting this search go to the google search for the way back machine just i'll show you this website but we won't actually use it if you go to way back machine whose url i never quite remember so there's this website which is wonderfully interesting if not a little scary archive what is it what's the domain here archive dot org the way back machine this is essentially a service that works to varying degrees of success that has been over the years archiving websites and it's sort of embarrassing you can scroll back in time and see like my college website and my terribly limited html skills at the time i think you can find old versions of the ones website from years ago and i don't know leave this isn't at home uh... uh... on endorsed home exercise if you look up dot dot dot white house dot com you might see old uh... versions of that website as well at least if you google around i'm sure people talked about what it was all about those of you have no clue uh... just ask the person next to you enough people seem to know what's going on right now anyhow tlbs are meant to organize hierarchically domain names in a way that gives you a sense of what kind of domain it is are there restrictions if you the user want to go and buy a domain name in dot net dot org dot com these days what kind of entity must you be to buy a dot org dot net or dot com a business for dot com ideally that was certainly the original purpose but it turns out these days no restrictions on any of those three so you can have dot coms you can have dot nets dot orgs owned by anyone which one you choose is really a matter of choice but really a matter of availability uh... as you will see when we get to the website development part of this course choosing a domain name at least one you want is a non-trivial matter one a lot of good names have been taken up by actual websites and companies to a lot more domain names have been perhaps been taken up by squatters folks who have just bought these domain names like uh... thinking that someday someone will come knocking and want to pay them more than the seven dollars a year or so it's costing them to maintain it hoping to cash in on the thousand dollar domain name or the million dollar domain name or even something more than that so you will perhaps feel that frustration when you seek out your own domain name turns out among the tlbs you can choose from these today are many one of the best registrars that i've used in my experience to register a domain name is go daddy it's a goofy name in the websites kind of overwhelming because they try to upsell you every time you visit a page but if you sort of ignore all of the upsells and just seek out your six ninety five or eight ninety five domain name you can get a good deal and they have a very good interface for managing domain names you might own and again we'll come back to this in our website lecture but for tonight i just wanted to show you the drop down if the name is available you are allowed these days to register a website in any of these tlbs and more than these in fact go daddy doesn't necessarily uh... allow for doesn't necessarily let you register all the available ones but if you want to host you know david mail in dot jp if it's available you can create the illusion in effect by name that your website is in this is only to say that tlbs though originally intended to create very obvious hierarchies very obvious distinctions has begun to relax somewhat each country gets to manage its own domain and in fact if you've ever been to something like uh... uh... what's a website that uses anything that ends in dot t v ever been to a website ending in dot t v well dot t v is the domain name that belongs to a little uh... southeast pacific uh... country that decided to sell off the rights effectively to its domain name because at least in the english-speaking world dot t v can perhaps fetch a pit pretty price for tv shows if nothing else so i'll leave that as an ad more a family friendly at home exercise if you'd like to figure out what country it is that allows you to register names in the dot tv tlb uh... hand went up earlier and very interesting question many websites these days don't even have the w w w anymore in fact if i go to cnn dot com i will get the day's news if i go to and i stop that intentionally because i always say cnn dot com because it's so such a short domain name to type during lecture but i've made a mistake for years of pulling up the current events on the news and then all that interest goes up there so we won't see what's going on in the world now but if we go to go daddy dot com it's probably gonna pull up w w w dot go daddy dot com if i pull up just craigslist dot org it too will if i pull up well let's do uh... what we do cnn dot com if we pull up instead dub dub dub dot go daddy dot com well that too works well long story short back in the year rid the days of when the internet was first becoming popularized you would often see url is described as h t t p colon slash slash w w dot cnn dot com well the world relatively quickly acclimated to the fact that okay i know that this means go on the internet so gradually you saw h t t p colon slash slash being dropped what that is will come back to in this course and so you just saw w w w dot cnn dot com well that sort of a mouthful and even that's w w w sort of becoming gratuitous today because if you see dot com you know unless you have not been paying attention for several years you know what that means and what that is so the dub dub dub has been dropped and technologically it is very easy for you to set up a website that either uses dub dub dub or doesn't use it and what good well managed websites do these days is they let you visit both and they'll usually route you to the same location and just like what happened with go daddy if go daddy just likes to present itself to the world as dub dub dub dot go daddy dot com they'll use a server side trick to just change the url on you just so that they present some unified marketing fate uh... in uh... marketing if you visit a website or try to visit a website like david mail in dot com and hit enter and it just doesn't work even though dub dub dub dot david mail in dot com does work frankly that's just a stupid decision by the administrators of the website because it appears that the site's broken when really they haven't flipped a switch that makes the uh... version of their url work the dub dub dub and in fact on that note why don't go ahead and take a five minute break and when we resume we will dive in deeper so we have our basic building blocks tonight of what a network is it's a bunch of computers connected together you can describe a bunch of computers connected together by way of a domain name so harbor dot edu but let's actually consider what some of these components are so that some of these matters like do you need the dub dub dub do not need it start to make a bit more intuitive sense if i write down something like w w w dot cnn dot com again softball this is the part of underlined is the top-level domain the tlb right and in general it's a kint as to what kind of website it is though to be clear earlier even though you can choose a website these days in dot org dot net or dot com i would wager that to this day the most popular is dot com if only because at least for those individuals who don't really appreciate that it doesn't matter for the most part what your tlb is these days they think they see dot com they think website they see dot net dot org might not necessarily be as clear to the person off the street that that is for instance a website they should visit but i would argue that even that potential confusion is going away in time uh... so this is generally called the domain name this is called the host name if you're talking about the address of a website it's usually broken up into the host name and the domain name part of which is the tlb but it is certainly possible for a website to only have this part which means that it effectively has no host name which is to say when you visit cnn dot com the server configuration is such that it just routes you to a computer that is nameless in a sense but is in effect cnn's web server or the server can simply add that w w w and just make more explicit the host name what do we even mean by host name well how many servers do you think cnn has so they typically have a lot any of these big websites they don't just have one big server as i drew it on the board today they have a lot of smaller but very fast if not very inexpensive servers google works in this way but with thousands of computers but you don't have to know the name of the google server that you happen to be searching on you just go to google dot com or dot dot dot google dot com and their various server side configuration tricks when you go to google dot com your search query for whatever it is you're searching can be routed randomly or in some special fashion to one of these computers well computers like people tend to have names so that you can refer to them and say all the alpha machine is broken or the donald machine is broken right computer people uh... you'll see tend to give nick uh... their computers goofy names though my laptop as you've seen by contrast is called laptop so when you have multiple computers just handle the sheer demand for your website you don't want to advertise the names of all of those computers you want to just present one unified face to the world whether it's dub dub dub dot cnn dot com or cnn dot com but as soon as you hit enter and your browser tries to visit this website cnn's infrastructure routes you to one of those computers and this computer it sends you to might be called w w w one dot cnn dot com w w w two dot cnn dot com it's entirely the prerogative of the owners of that server but for the most part you the user don't ever see the host names of most of the computers that you're in effect being connected to when you visit a website or when you use some other internet-based technology dub dub dub hostname is the name of the computer and a website doesn't necessarily have to have a hostname associated to summarize but you also see addressing schemes like this not just for websites right after web what is the next most popular internet program you might use every day email is a big one well email similarly makes use of domain names and tlds and even what look like host names but rather if you send an email to mail in at f a s dot harvard dot edu well here again as a tld debt ddu instead of dot com here's a domain name and what do we say this is called so this is a sub domain so in the context of web addresses you would usually call the first thing if it's not the domain name itself the host name it's the name of the server that you're visiting but really when you send an email to someone you really don't care what machine that email is getting sent to you care more conceptually that that email go to the right domain and so in that sense and it's a slight distinction when you send an email to mail in at f a s dot harvard dot edu your email goes to whatever server it is on the internet that manages email for this domain specifically this sub domain okay okay so it's a good question and to summarize it sounds like you have someone on one of your email lists that is receiving your emails but is complaining that they don't want to receive your emails but that person's the sub domain of that person's email address just so happens to be this same what happens to be the same the username so the you have this user who wants to opt out of your email list for because for some reason she's getting some emails that are clearly meant for someone with a similar username but a different sub domain or domain name so i can only hypothesize that either one there's some kind of typo going on a slight distinction or perhaps more likely is one of the email addresses on your mailing list is forwarding to maybe her address and maybe that person made a typo and are thus forwarding their emails to the wrong person but without actually seeing the data it's hard to be more accurate than that if you want to send us an email if you are allowed to reveal the details we can try to advise okay we'll get that woman off your list soon enough okay guess that will be the challenge indeed so probably everyone in this room uses email at least once a day or perhaps too frequently more frequently than you would like well some of these questions might seem pretty easy but at the end of the day these are perhaps common points of confusion at least for neophytes what does a typical email address look like there are two canonical forms if you have an email address it probably looks like the first one with just that domain dot com like david at gmail dot com don't email that it goes to some other david or you can email some username at some subdomain dot domain dot tl d and you can have multiple subdomains but after a while it starts to get ridiculous and so you don't tend to see them that often so these would perhaps be the two most basic forms so a bit of a quiz these are examples of legitimate email addresses they might not go to real people but syntactically these are valid syntactically correct email addresses you know frankly these days on the internet i bet one of these goes to every there's probably someone that gets each of these emails that may be another at home exercise email these people and see what kind of curious individuals you get back replies from so those are valid email addresses points to take away are perhaps implicit so clearly you can use letters of the alphabet you can also use numbers what other characters are clearly valid characters in an email address underscore what kind of symbols symbols in general to general be more specific so underscores which is that under bar which creates the illusion of a space but is just kind of a hack around it what else is clearly valid a hyphen is valid uh... in and that uh... the m dash here it's actually it would just be a hyphen in this case but sure uh... forward slash would not be valid in an email address no slashes in email addresses ever you clearly need the outside that's in both of the canonical forms we looked at what do you not notice here well there are not things like spaces spaces are not allowed there are not things like dollar signs or what you might think of as weird characters it's fairly safe to say that these are most of the valid symbols that can appear in an email address but notice you can have a period and it has different meaning to the left of the aton to the right of the act to the right of the ad it has some clear conceptual distinction it's sort of a demarcation between the tlb in the domain and maybe a subdomain on the left-hand side it's completely arbitrary people use dot sometimes in lieu of underscores just because they like to look better but there's no inherent meaning if it's david dot mail in that's just because david mail in fought the dot maybe looked better than no no character at all maybe better than an underscore harvard arbitrarily for those of you who are staff arbitrarily chose to make email addresses of the form david underscore mail in at harvard dot edu for instance capitalization doesn't matter it does not it is tacky dare say to email someone with their address all capitalized it's sort of silly with some people right through email addresses like the mail in if only because that's not really consistent with convention but there's nothing wrong with it email addresses are case in sensitive you can capitalize don't capitalize it really doesn't matter at least for this part of the domain but i have yet to meet a mail server that doesn't ignore capitalization in the user name though theoretically you could design a server that would make the distinction but i wouldn't think on that too much take a moment which of these are syntactically valid so is a good time for and you can't see them which of these are syntactically valid okay we'll jump right into it okay j at nbc dot com is that's fine is syntactically valid tried to throw you off with the capitalization but completely legitimate uh... mine being mail in a post at harvard dot edu good somebody at franklin dot m a dot u s so that's an interesting point of discussion if briefly that looks like it's somebody from where yeah franklin massachusetts so it turns out that in addition to t l d is like dot org and dot com and dot gov there are also two-character tl d's and these are generally called country code tl d's and we mentioned one earlier even though it's sort of abused these days with permission dot tv is technically a country code and it is tl d it was originally under the control of just one country and it is still but they've allowed anyone to just use it even the u s has their own tl d dot u s and a lot of uh... governmental entities like local townships if you have a city oriented website uh... the mayor's office those sorts of domains even though they could be in most any tl d even dot com if they wanted to just send a weird message well dot u s is common for municipalities and so forth dot m a dot u s is for massachusetts and franklin dot m a dot u s in denotes franklin massachusetts in the united states but if we have dot u s why do most websites in the united states seem to end in just whereas if you go to cnn in the u k you would instead visit something like cnn dot co dot u k or i think cnn dot co dot j p if i'm remembering them correctly so co in a lot of countries that's the convention they adopted it just denotes commercial they didn't choose calm but it was sort of arbitrary no cnn's website in japan the one that brings up japanese text is not cnn dot com that seems to be the u s one in fact you bring up most dot coms though that might be slight exaggeration these days many dot coms they pretty much look like english based united states based websites why is it that the united states has this sort of luxury of not needing to use their country code all over the place and we were the first ones there i mean it's sort of what it boils down to who is the internet invented by not al gore who right the guard the internet grew out of what on the u s military project originally called art but not advanced research projects association forgetting the acronym right so it was originally a military project that was designed in this in effect to allow computers which at the time were huge and expensive and slow to communicate throughout the country it was designed in a way that allowed for redundancy so that if one server or one city even were taken out the rest of the network in theory could continue to function and that's why today and especially next week will look at the interconnections that exist on the internet there's so many different ways to get from point a to point b and it sort of looks like a mess but that's a really good thing for dealing with problems if servers go down if connections break and so forth and that grows out of to some extent a military mentality having redundancy having the ability with to withstand nodes or computers being taken offline for whatever reasons well fast forward to today popularized the internet was by universities using it after that and now typical people in the mid nineties and so forth and so for the most part just the u s happened to set most of this stuff up can you live in japan or in the u k and have a dot com yes so dot com dot org dot net just as you in american or most of you americans can buy a dot com and use it here so can most anyone else so there really aren't restrictions on a lot of these tld's these days that sort of broken down uh... partly for financial reasons i'm sure bigger audience you have to sell to the more money you can make and partly just because networks are getting larger and more nebulously defined so i'm sure you can say other reasons for but know that doesn't necessarily mean that a website is here if it ends in dot com anymore can end up anywhere okay back to the list at hand somebody is correct mail in is correct jay is correct what's wrong with the other three spacey and affidavit that one won't work the dave at cbs is missing the ever important tld you don't need a subdomain you do need a tld and finally what's wrong with user the exclamation point right if it looks kind of funny it's probably not legitimate these days periods underscores hyphen plus is valid though it often has special meaning and you don't see it in most normal people's email addresses etiquette so goofy sort of word adopted years ago what is netiquette all about and this is very much related to again tonight's theme of the internet and the usage thereof not necessarily the implementation thereof what's netiquette yes internet etiquette right not hard to come up with that word do not if you are new to email or if you're not new to email but have been doing this for years do not email people in all capital letters even if your caps lock he happens to be on by accident take the time to turn it off and retype your message or at least be aware of what's appearing on your screen uh... i don't do it now so much now that we film these lectures but for years i would offer uh... family anecdotes of people in my family who would do these kinds of things i'm not allowed to say who in my family to this day still does such things like this because i didn't realize the caps lock he was down considered bad netiquette what does it imply if you receive an email in all capital letters that's your shot i mean more likely these days is just your not your doofus but it implies shouting uh... related to uh... email usages of course spam for a while we had to find what spam is i think it goes without saying what spam is today it is a huge huge problem on the internet today to the extent that it uses up so much bandwidth and you wouldn't think so based on the emails because they're pretty small usually a few kilobytes if even that a couple paragraphs maybe a small image attached you send out a million of those small emails and you do it all the time or you send out ten million of those emails because at the end of the day the marginal cost of sending one more email is pretty much zero cents that's pretty good marketing technology if you can at nearly zero cost spam thousands or millions of people even if only one percent of those people are clueless enough as to click on the email or buy whatever it is you're spamming them with one percent of a million that's a lot of people and it might be worth your while especially if the cost of doing so wasn't even all that expensive this is an example of spam those of you who are in debt might take heed from this particular email you get all sorts these days about that uh... viagra cialis uh... what are the other popular ones that you get every day i'm sorry okay porn is popular to you get those as well without uh... for loans all yes the nigerian was at the four oh nine scams it has a name that refers to the part of the penal code that describes those kinds of scams and you read every year like an article will come up where there are people who have been duped by these things into losing tens of thousands of dollars or even their life savings and spam though besides being a sort of a sociological problem for various reasons it's also a technological one because what are you increasingly seeing in your spam or tell me about a typical spam it probably doesn't always look like this these days what do you often see if you scroll down farther a bunch of addresses perhaps what else has perhaps confused you about spam you've received sometimes okay so it's often it often has bogus return addresses which is problematic because you don't know until you reply and incidentally before i forget a lot of spam from non-legitimate companies will often include links or instructions say reply to this email with unsubscribe in the subject line to unsubscribe or click this link unsubscribe uh... if you learn nothing else tonight know that you should never click links in spam to unsubscribe because what are you effectively doing by risk to replying to spam or clicking that unsubscribe link right you're confirming to the spammer that you know what you just got a sucker there and you're gonna get more spam potentially because of it sounds like a nice idea to be able to opt out but generally if you inform the spammer proactively that hey i want out what you're really saying is high i exist because a lot of these emails especially in domains like hotmail and gmail and yahoo the really popular domains a clever spammer will just start to email randomly generated email addresses because if you have millions of customers like hotmail probably does well odds are that even if you guess a lot of them some of them are going to actually be d a v i d or somewhat more cryptic but nonetheless a valid email address and so it's to a spammers advantage if you proactively tell him or her hey you got a good one yeah good question how do spammers get email addresses one is randomness to if you go on the ones website you can call at least two or three email addresses mine raise the course email address anytime you publish an email address on a web page if you uh... are a spammer you would use what's called a spider or a bot which is just a program similar to what google and reputable companies use to crawl the internet to index it's for subsequent searching but you can write a bot or spider that just calls the internet looking for email addresses after all you the students know that any email address is unlikely to be of one of these forms not hard to write a program that just looks for that pattern on a web page grabs it and then adds it to a spammers database so that's one other way as well uh... if you have a hyperlink on the web page with which someone can email you it's the same thing even if you don't see the email address it's embedded in the so called html and a program can find it you'll see a lot of websites will say email me at mail in and it'll put a space or two they might write at and then they might say harvard dot edu whether i would bet you know there's enough spammers in the world someone's probably taken the time to modify their program to also look for things of this format which means they can figure out that you're just trying to trick them what other websites will do especially websites like the face book or a lot of these uh... personals types websites where they might list your email address they won't show your email addresses text they'll instead convert it to a jpeg or jiff that is an image so an image isn't something that you can just highlight like you can with microsoft word you would have to figure out what that image is actually representing it's similar in spirit to um... you've ever visited those websites and in order to confirm you have to type in that cryptic the squiggly words and numbers which sometimes are too squiggly to even understand correctly same idea the idea with those is that it's hard for computer to figure that out similarly if you show the email address as an image it's marginally harder for computer to figure that out or at least it takes more cpu cycles to process that kind of thing personally i don't care anymore about posting my email address everywhere on the internet i actually think that there is a technological solution to this problem and that though it's very reasonable to say it though it's very reasonable to assume that your will you will get less spam if you don't publish your email address in printed forms or on web pages that's a hard thing to prevent all of the time especially if you want to keep an email address for years and only takes once or twice for it to get slurped somehow and then just get propagated through databases and anti spam software is definitely getting better i mean i get probably five hundred a thousand total emails a day many of which are spam two hundred of which tend to be real emails and among those two hundred real emails that actually i see in my inbox i would say on a typical day i get four to six spams these days and i actually think that's pretty good i'm rarely having to delete them so in short eat spam detections getting better fundamental problem is that email was not designed correctly to deal with this problem there is no security implemented in email and the fact that spam is such a problem is because there was no forethought given or at least well implemented there was no uh... this was not raised as an important issue initially and that's partly because no one saw many people didn't see the internet becoming used by people like you and me and who's going to want to email a few hundred researchers who are using the internet research purposes that's part of it as well uh... another example of spam if you're uh... finding you want a little too much work you can call the number on your screen or wait for the spam to arrive and you can cash out with your degree much more quickly than any kind of university program and there's a whole bunch of others these days only so that we can slap another piece of jargon on it what is an emoticon without looking down at your papers to smiley face so this is a non-exhaustive list of the emoticons that people have not only come up with a word for but also uh... all the different emotions that they might express the only one that we like to point out each year is somewhat apropos is one of them's funny this one too is kind of funny only because here we are tonight so uh... feel free to assert any of those as your own in future emails okay so let's do this let's pause for five minutes so i can turn your attention to one of the white pieces of paper tonight this is a survey the course is you know offers sections and workshops one we'd like to just get some feedback from you now for no more than five minutes on what you think of the course what you think of the lectures but most importantly to be honest why you are or not going to sections or workshops just to give you the historical perspective when i was a tf for this course years ago we had three or four sections of fifteen or twenty students and fifteen or twenty students were attending each night and we'd like to think that we're not just doing a bad job these days but that there's more interesting issues involved as to why students in the class tend not to be as interested in the courses sections and workshops anymore perhaps it's more savvy perhaps it's because of scheduling but if you could just give us your candid thoughts don't put your name on them it's not necessary we would love to understand what you like and don't like and what's driving you to come or not come to these things i'll even put on a bit of uh... background music so ten uh... this week's section is going to be on exploring the internet uh... this weekend next week in lecture david goes kind of that quickly through uh... uh... the internet and how things work and we're going to take a little time to explore things uh... both a little bit deeper for those uh... who feel comfortable with the pace at which david's going and uh... take up a breather to to review some things uh... that he's already covered uh... for those of you who'd like to go uh... so we're gonna explore the internet talk about how email works talk a little bit more about how web servers work that sort of thing and this saturday's workshop be led by dan this saturday will have a workshop on uh... mac os and i invite i invite all of you to come doesn't matter if you have never seen a mac before or if you think you are quite a bit savvy i guarantee you'll learn something uh... we'll talk about the macOS itself will talk a little bit about uh... apple the company will talk about the intel switch will answer any questions you have basic troubleshooting there's a lot that we're going to cram into two hours so i hope to see all of you there fantastic and finally this sunday we have a back-to-back workshop dan's is on saturday on sunday at eleven a m we will all meet if you are interested at the kennel square kennel square t-stop for a field trip of sorts to mit swap fest this is something that happens every month or so up until the month between i think april and october will post a link to more details on the course's website on the lectures page but the short of it is that this is a wonderfully fun low-key uh... afternoon where you see a lot of crazy guys who have a whole bunch of stuff in their basements and garages and vans that they drive up to a lot at mit with an every month uh... have stuff to give away to sell and we're talking all the electronics old computer parts really interesting because you can ask questions of these types of folks who really know their stuff on things about radios and computers and other types of system so if you're at all geek or you'd like to take a stroll through uh... yesteryear's hardware and just have a good time and will grab lunch or something afterward uh... do feel free to attend will do rsvp's over email just so we know how many to expect roughly but question one on this survey is just about whether you think you would join us this sunday at eleven a m and you'd be welcome to bring uh... dates as before our family and friends and so forth uh... turns out that problem set three which was distributed this evening is due this evening in fact an hour and a half ago so that's my fault uh... per the syllabus this is actually do on wednesday twenty five october so you have two weeks not t minus one point five hours to do it so my apologies will update that on the website for problem set three which was just handed out tonight so there's just a couple other things that are in the slides i'm gonna skip over ssh and s ftp because we'll come back to that but just so that we tie wrap up this discussion and i want to conclude with a really neat demo let's uh... look at the ever-enlightening slide on the worldwide web so what is the worldwide web so the network of all networks so the answer to that is actually now and this is where you can make a subtle but useful distinction the web or the worldwide web and the internet they're not the same thing so what you just described actually was a perfect definition of the internet a network of networks but the internet is really in infrastructure something that takes physical form and is the physical incarnation of as what we've described as the network of networks of networks it's sort of the the backbone on which a whole bunch of neat services run and the worldwide web is an example of such a service it's something that you can do with the internet something on the internet and i would like in it to other internet-based services like email and instant messaging and podcasting these are sort of higher level programs if you will or services that you do using the internet but the internet itself is really that uh... infrastructure underneath the hood a url is something that you probably have typed every day uh... here's another uh... i won't name names within the family do not call this an url uh... it's really difficult to keep a straight face when someone in your family is asking you to pull up the url dub dub dub dot cnn dot com it's a url uniform resource locator you don't have to know that but notice a url even though it's the more inefficient way of saying it the canonical form is this and we'll see other incarnations of this but when you see something colon slash slash something pretty much refers to a url and even though you a typical user might only see things that are http colon slash slash something it turns out that you can have urls of other formats for other types of services most of which typical users don't use but one of which you will use later in the course namely ssh or even sftp can be written in this way but more on that in the future some examples all of these are valid urls these are all valid addresses of servers so essentially a url even though you almost always see it just for the web it's really a general way of describing the protocol that you must use to talk to a machine a protocol as suggested up there is just the language that your computer needs to use to access the service so when you are the user use internet explorer to pull up cnn dot com the language that your computer and that server are using to communicate is called http hypertext transfer protocol or transfer protocol this is just uh... you know it's like english is to us we have a way of communicating with each other by the standards known as english computers specifically web browsers and web servers have their own language called http that they use to speak back and forth to one another think of it as the language that you might have to use to order meals in a foreign restaurant with a foreign waiter and meanwhile underneath that is html which we will come back to on our website class html by contrast is the language that web pages are written in so whereas you might speak french in a french restaurant to the waiter if you were to hand him a note or rather if you were to have this analogy is very quickly going to break down let's not even try to use an analogy and focus tonight just on http which is the language that web browsers and web servers use to communicate and leave it at that so some examples of protocols and sites that one can visit are these food dot com food dot com with or without with or without the host name capitalization you see in the third row doesn't seem to matter you can have slashes in url's and in fact when you see a slash it's usually because you have something like the uh... example uh... look at that none of these actually have the example if you have something like uh... http colon slash slash food dot com slash bar slash index dot html especially if you're a pc user you've seen things that look like this but you've probably seen things like c colon backslash program files and so forth so these are both just pads they tell you where something is on the internet just like this tells you where something is on your hard drive use the language http to access this information the server is called food dot com that's also the domain name but again you don't necessarily need a host name it's up to the server administrators is take a guess what does this represent think about what this is this is just a folder on that web server this is just a file in that folder and as you'll see when you start making web pages in this class you will be creating text files called something dot html and in that file will you write your web page you can put it in a folder in your domain so it could be david mainland dot com slash something slash my page dot html but the only reason you would use folders is just for the reason you would use them on a local computer just to keep things neat and tidy and organized that's really the only reason but notice this you can visit i'll do it anyway you can visit cnn dot com hope nothing bad has happened if you visit can't win if you visit not just cnn dot com notice and it's going to be small text cnn dot com slash index dot html really have to pick a new demo for next year like yesterday's news index dot html tends to be the default name for most home pages so even though you don't always have to type it because in the absence of specifying what file you want a web server will usually give you some default file name which happens to be as you see here index dot html but more on that in our internet actually i'm gonna close the headline so we get back to this so with that said and we'll focus on just on a couple of these before our final demo which of these are syntactically valid is the first one no slashes are in the wrong direction here's another way to make sure that tech people don't laugh at you behind your back this is a forward slash this is a backslash do not confuse them it's a silly semantic thing but if you start calling forward slash is backslashes and backslashes forward slashes the person if they are a technophile you're talking to you're gonna lose some credibility very quickly uh... and i actually have an example photo that i'll bring in next time what you also don't want to do is make mistakes not even verbally or semantically but when i was home in connecticut once i went with my mom to bed bath and beyond and they had in their window a really big and probably expensive poster advertising their new website as bed bath and i think i got that backwards beyond dot com right probably two hundred five hundred dollar sign in their window advertising their website visit us at bed bath and beyond dot com is bad marketing that is not a valid url you type that into a web browser you will not go to bed bath and beyond this obvious reason perhaps being what character is not allowed in urls the ampersand i don't know what marketing genius got this wrong when you are advertising your company best to advertise the correct url that will not work it was in fact a and d that they meant to write so funny things so again there too if you sort of next time you walk into bed bath and beyond you know just smile to yourself if the ads still happens to be up and try to explain to the manager why it's really come down because frankly it's we sort of make fun of it but a stupid little thing like that if you are an uninformed user and you say i a bed bath and beyond you pull this up doesn't work now that's bad business you're probably not going to go back at least for a while so sales might be lost uh... middle one of the second one dot dot dot bar dot com says the sort of a trick question it's not officially a url because it's missing the protocol specification but it turns out these days you don't need to type it at least in a browser technically when you visit a web page like we just did with cnn you're visiting a url but most of us probably don't bother typing http colon slash slash anymore because you just don't need to browsers if you don't specify a protocol assume that you want http because after all you're using a browser in the first place but it turns out there are other types of urls ftp is another protocol file transfer protocol you'll use this later in the term but that's just a program with which whose sole purpose in life is to let you copy files from your computer to some remote and you would access that via ftp colon slash slash but this last one not valid why is it not valid wrong slash so one slash rather than two actual slashes what i will do will keep a couple of the remaining things for next time but in the remaining two minutes i just wanted to wow you if you never use this before so let's very quickly how well when you've had to look up directions where what websites do you tend to use these days okay i heard google maps and i heard map quest so i google maps tends to be the best not necessarily in terms of the directions they provide but just in the aesthetics the maps i would say subjectively look so much better than map quest or yahoo's ever did and that's enough reason i think to try this site out if we search for one oxford street in cambridge mass of two one three eight if you've never used a website like this before the beautiful thing about google maps like these other sites is it whips whisks you right away to it and then you can scroll around you can zoom in these days you can actually click satellite and actually get satellite version of the same area and this is literally going to be sixty second teaser if you think things like this are cool the note i'd like us to end on tonight is another one of these applications the services we talked initially tonight about networks and the internet and then a couple services on top of it the most popular perhaps email and uh... the web we use victor as an example of using skype voice over i p is another program well if you download and this is more of a software product in a specific service if you like this sort of thing downloaded will provide a link to it google earth which is software that google actually bought from another company i spent two hours this after preparing for a lecture looking up with this program for one thing we can start in again the science center okay that was helpful uh... there we go you can see that uh... wait second work too big let's go back to this video come on where is the science center on earth so when you can zoom in even for and i i swear to god this whole lecture would have been about this program had we started with it and not ended with it this is my way of self-regulating so here's the harvard science center you are roughly over here in the building where my cursor is you know cambridge massachusetts might be fine and all but let's just for the sake of it zoom on over to all how about venice this is just a brilliant interface and the coolest thing i've seen today frankly and here we are in that i was taking a little vacation in my apartment this afternoon so here's venice you can zoom out and i'll leave you to play with it like you can change angles and the software sort of interpolates things will look very flat which is not what venice looks like it is sinking but it's not entirely flat but the software and this is an example of really neat tricks with fast processors is giving you different perspectives based on its inference of what the landscape looks like alright italy's interesting let's zip on over to new york and again will provide you with a link to this on the website it's entirely free takes a couple minutes download you install it's a wonderful way of spending time in the middle of the day or frankly with kids to i think we get a real kick out of this and the reason actually i brought this up this afternoon is i'm auditing an archaeology course at the college this semester and the professor for the first time today use this as an example of showing us uh... the pyramids of giza the uh... wait i got one last one oh here we go the great sphinx and the photography the aerial photography and satellite imagery isn't perfect right you can't totally zoom in and see things like you could on the ground but my god from an apartment in boston to be able to take being able to take this virtual tour of the world with such a neat clean interface there you see it is the great sphinx so on that wow factor why we call tonight and we'll see you next week