Computer Networks: Crash Course Computer Science #28

hi I’m Kerry Ann and welcome to crash course computer science the Internet is amazing in just a few keystrokes we can stream videos on YouTube hello read articles on Wikipedia order supplies on Amazon video chat with friends and Suites about the weather without a doubt the ability for computers and their users to send and receive information over a global telecommunications network forever change the world a hundred and fifty years ago sending a letter from London to California would have taken two to three weeks and that’s if you paid for express mail today that email takes a fraction of a second this million fold improvement in latency that’s the time it takes for a message to transfer juiced-up the global economy helping the modern world to move at the speed of light on fibre optic cables spanning the globe you might think that computers and networks always went hand-in-hand but actually most computers pre-1970 were humming away all alone however as big computers started popping up everywhere and low-cost machines started to show up on people’s desks it became increasingly useful to share data and resources and the first networks of computers appeared today we’re going to start a three-episode arc on how computer networks came into being and the fundamental principles and techniques that power them [Music] the first computer networks appeared in the 1950s and 60s they were generally used within an organization like a company or research lab to facilitate the exchange of information between different people and computers this was faster and more reliable than the previous method of having someone walk a pile of punch cards or a reel of magnetic tape to a computer on the other side of the building which was later dubbed as sneakernet a second benefit of networks was the ability to share physical resources for example instead of each computer having its own printer everyone could share one attached to the network it was also common on early networks to have large shared storage drives ones too expensive to have attached to every machine these relatively small networks of closeby computers are called local area networks or lands and LAN could be as small as two machines in the same room or as large as a university campus with thousands of computers although many land technologies were developed and deployed the most famous and successful was Ethernet developed in the early 1970s at Xerox PARC and still widely used today in its simplest form a series of computers are connected to a single common Ethernet cable when a computer wants to transmit data to another computer it writes the data as an electrical signal on to the cable of course because the cable is shared every computer plugged into the network sees the transmission but doesn’t notice the data is intended for them or another computer to solve this problem Ethernet requires that each computer has a unique media access control address or MAC address the unique address is put into a header the prefix is any data sent over the network so computers simply listen to the Ethernet cable and only process data when they see their addressing the header this works really well every computer made today comes with its own unique MAC address for both Ethernet and Wi-Fi the general term for this approach is carrier sense multiple access or CSMA for sure the carrier in this case is any shared transmission medium that carries data copper wire in the case of Ethernet and the air carrying radio waves for Wi-Fi many computers can simultaneously sense the carrier has the sense and multiple access and the rate at which the carrier can transmit data is called its bandwidth unfortunately using a shared carrier has one big drawback when network traffic is like computers can simply wait for pilots on the carrier and then transmit their data but as network traffic increases the ability that two computers will attempt to write data at the same time also increases this is called a collision and the data gets all garbled up like two people trying to talk on the phone at the same time fortunately computers can detect these collisions by listening to the signal on the wire the most obvious solution is for computers to stop transmitting wait for silence and then try again problem is the other computer is going to try that too and other computers on the network that have been waiting for the carrier to go silent will try to jump in during any pause this just leads to more and more collisions seeing everyone is talking over one another and has a backlog of things they need to say like breaking up with a boyfriend over a family holiday dinner terrible idea Ethernet had a surprisingly simple and effective fix when transmitting computers detects a collision they wait for a brief period before attempting to retransmits as an example let’s say one second of course this doesn’t work if all the computers use the same wait duration they just collide again one second later so a random period is added one computer might wait 1.3 seconds while another weighs 1.5 seconds with any luck the computer that waited 1.3 seconds will wake up find the carrier to be silent and start transmitting when the 1.5 second computer wakes up a moment later it’ll see the carrier’s in use and will wait for the other computer to finish this definitely helps but doesn’t totally solve the problem so an extra trick is used as I just explained if a computer detects a collision while transmitting it will wait one second plus some random extra time however if it collides again which suggests network congestion instead of waiting another 1 second this time it will wait 2 seconds if it collides again it will wait 4 seconds and then 8 and then 16 and so on until it’s successful with computers backing off the rate of collision goes down and data starts moving again freeing up the network family dinner saved this backing off behavior using an exponentially growing wait time is called exponential back-off both Ethernet and Wi-Fi use it and so do many transmission protocols but even with clever tricks like exponential back-off you can never have an entire University’s worth of computers on one shared Ethernet cable to reduce collisions and improve efficiency we need to shrink the number of devices on any given shared carrier what’s called the collision domain let’s go back to our earlier Ethernet exam Paul where we had six computers on one shared cable aka one collision domain to reduce the likelihood of collisions we can break this network into two collision domains by using a network switch it sits between our two smaller networks and only passes data between them if necessary it does this by keeping a list of what MAC addresses are on what side of the network so if a one’s transmitted to see the switch doesn’t forward the data to the other network there’s no need this means if he wants to transmit two F at the same time the network is wide open and two transmissions can happen at once but if F wants to send data to a then the switch passes it through and the two networks are both briefly occupied this is essentially how big computer networks are constructed including the biggest one of all the infinite which literally interconnects a bunch of smaller networks allowing Internet work communications what’s interesting about these big networks is that there’s often multiple paths to get data from one location to another and this brings us to another fundamental networking topic routing the simplest way to connect two distant computers or networks is by allocating a communication line for their exclusive use this is how early telephone systems work for example there might be five telephone lines running between Indianapolis and Missoula if John picked up the phone wanting to call Hank in the 1910s John would tell a human operator where he wanted to call and they’d physically connect John’s phone line into an unused line running to Missoula for the length of that call that line was occupied and if all five lines were already in use John would have to wait for one to become free this approach is called circuit switching because you’re literally switching whole circuits to route traffic to the correct destination it works fine but it’s relatively inflexible and expensive because there’s often unused capacity on the up side once you have a line to yourself or you have the money to buy one for your private use you can use it to its full capacity without having to share for this reason the military banks and other high importance operations still buy dedicated circuits to connect their data centers another approach for getting data from one place to another is message switching which is sort of like how the postal system works instead of a dedicated route from A to B messages are passed through several stops so if John Y is selected to Hank it might go from Indianapolis to Chicago and then hop to Minneapolis then Billings and then finally make it to Missoula each stop knows where to send it next because they keep a table of wet past letters given a destination address what’s neat about message switching is and it can use different routes making communication more reliable and fault tolerant sticking with our mail example if there’s a blizzard in Minneapolis grinding things to a halt the chicago mail hub can decide to route the letter through omaha instead in our example cities are acting like network rooters the number of hops our message takes along its route is called the hop count keeping track of the hop count is useful because it can help identify routing problems for example let’s say Chicago thinks the fastest route to Missoula is through Omaha but Omaha thinks the fastest route is through Chicago that’s bad because both cities are going to look at the destination address Missoula and end up passing the message back and forth between them endlessly not only is this wasting bandwidth but it’s a routing area that needs to get fixed this kind of error can be detected because the hop count is stored with the message and updated along its journey if you start seeing messages with high hop counts you can bet something has gone awry in the routing this threshold is called the hop limit a downside to message switching is that messages are sometimes big so they can clog up the network because the whole message has to be transmitted from one stop to the next before continuing on its way while a big file is transferring that whole link is tied up even if you have a tiny 1 kilobyte email trying to get through and either has to wait for the big file transfer to finish or take a less efficient route that’s bad the solution is to chop up big transmissions into many small pieces called packets just like with message switching each packet contains the destination address on the network so reaches know where to forward them this format is defined by the Internet Protocol or IP for short a standard created in the 1970s every computer connected to a network gets an IP address you’ve probably seen these as 4 8 bit numbers written with dots in between for example 1 7 2.2 17.7 dot 2 3 8 is an IP address for one of google’s servers with millions of computers online all exchanging data bottlenecks can appear and disappear in milliseconds network routers are constantly trying to balance the load across whatever routes they know to ensure speedy and reliable delivery which is called congestion control sometimes different packets from the same message take different routes through a network this opens the possibility of packets arriving at their destination out of order which is a problem for some applications fortunately there are protocols that run on top of IP like TC PYP they handle this issue we’ll talk more about that next week chopping up data into small packets and passing these along flexible routes with spare capacity it’s so efficient and fault tolerant it’s what the whole internet runs on today this routing approach is called packet switching it also has the nice property of being decentralized with no central authority or single point of failure in fact the threat of nuclear attack is why packet switching was developed during the Cold War today roof is all over the globe work cooperatively to find efficient routing –zz exchanging information with each other using special protocols like the internet control message protocol ICMP and the border gateway protocol BGP the world’s first packet switch Network and the ancestors of the modern Internet was the ARPANET named after the u.s. agency that funded it the Advanced Research Projects Agency here’s what the entire ARPANET looked like in 1974 each smaller circle is a location like a university or research lab that operated a Reuter they also plugged in one or more computers you can see PDP ones IBM system/360 and even an atlas in london connected over satellite link obviously the internet has grown by leaps and bounds in the decades since today instead of a few dozen computers online is estimated to be nearing 10 billion and it continues to grow rapidly especially with the advent of Wi-Fi connected refrigerators thermostats and other smart appliances forming an Internet of Things so that’s part one an overview of computer networks is it a series of tubes well sort of next week we’ll tackle some higher-level transmission protocols slowly working our way up to the world wide web I’ll see you then crash course computer science is produced in association with PBS Digital Studios at their channel you could check out a playlist of shows like brain craft community and PBS infinite series this episode was filmed at the chad and stacey emigholz studio in indianapolis indiana and it was made with the help of all these nice people and our wonderful graphics team is thought cafe thanks for the random access memories I’ll see you next time [Music]

Introduction to Networking

while I called tech support and they told me to unplug the router and plug it back in and well as you can see it you know I unplugged the router and I plugged it back in but hasn’t really done anything so I think this router is broken I think this is the router maybe maybe the router is this thing which one’s a router how what is any of this stuff anyway as we start using more and more sophisticated computing devices in our homes and small offices we need to think about the networking devices that are used to connect those computers those I pause those printers and everything else to each other and to the Internet networking devices are often overlooked things on the computer network that people just don’t think about very much this here is a Cisco router this is approximately a $500 device it doesn’t look cool it doesn’t look complicated there’s no there’s no holographs on here there’s no GPU numbers or CPU numbers but this device does networking very well it allows computers on the internal network to talk to each other and then get out on the internet and it does it like I say very very well this is a top-of-the-line product today we’re going to go over the devices that you will find in the average small network so whether you’re a residential client you’re a small business you will have these devices and these devices will be what allow your computers to talk to each other and then again get on the internet so this is an introduction to network in class and we’re going to go over the hardware and that the basic requirements to make your computers talk now the first thing that I’m going to talk about is I’m going to show you a basic diagram of how your your network next together and where the different components fit in so the first thing that we need to talk about is the internet cloud so the internet the internet cloud for all intents and purposes is the intranet so everything that you think of that is on the Internet whether it’s websites whether it’s virtual private network connections whether it’s email anything that you associate with the Internet resides in the Internet cloud so if you hear Internet cloud or cloud that is the Internet the reason we call it the cloud is the Internet is an insanely sophisticated system of networks and nobody really understands how it works it’s very complicated you can go on days and days and days and days in class on how the internet works so instead of going into all that we just call it the internet cloud so if you hear of the internet cloud or like cloud computing or any of that all that means is that the cloud is the internet so if you’re dealing with a cloud application that means that application is within the Internet so Internet equals cloud cloud equals Internet now the first device then that will be on your network the very first device that will connect your computers to the Internet will be it your modem so your modem is the first device that you own that that’s that’s part of your equipment that will connect you to the internet now behind that will be something called a router so this is another device that you that you will own that you will have and the router then then connects to the modem underneath your router you will have something called a firewall a firewall is a protective device that prize protect your network from hackers so that would be underneath the router underneath then the firewall will be something called this switch the switch you can think of the switch as a splitter of the internet signal so you can we’ll go into this in class you can have however many computers connected that you want but all of your computers or devices will connect into the switch and then the switch will then either allow them to communicate with each other or to go out onto the internet another device that will be on your network is of course a wireless access point the wireless access point will allow wireless computers and devices to then connect to the network so they will connect to the wireless access point which connects to the switch and then they can communicate either to other devices on the network or to the internet so basically you’ll have your computer that goes to a switch that goes through a firewall that goes through a router that goes through a modem and then you get to the internet so this seems like a lot of stuff it gets easier but this is this is the overall concept and diagram about how your network looks before we go any further I want to go over two concepts that always confuse everybody and it just makes everybody really frustrated so if we go over those concepts now hopefully you’ll be less frustrated later problem but you may be the first things we’re going to go over are we’re going to talk about speed and what it means and then the difference between something called a physical and a logical so let’s go over the concepts of physical and logical first within the the computer world we talked about about let’s say like computer devices and how they they connect to each other in the physical way and then in the logical way and what you need to understand is that these two things are not necessarily the same thing and many times are very very very different so the physical way that computers connect are you have let’s say you have a computer and then you have a network cable and that network cable physically runs all the way back to a switch summer and that switch is physically connected to a router and that router is physically connected to something else what you saw connected to something else so that computer is physically connected to the switch which is connected to the router etc well within the computer world we can also split things up logically so let’s say you have 20 computers and they’re all connected to the same switch well they are physically all connected to the same switch but what we can do in the computer world is within that switch we can put let’s say we can split those computers down the middle and put half of the computers ten of the computers logically onto one network and the other half logically onto another network so although the computers physically come together they physically they connect into that one switch logically they’re not able to talk to each other because it’s it’s split in that switch so when we do diagramming we’ll split everything out like I showed you the internet cloud the modem the router the firewall the switch and that is logically what happens those are logically all the different devices that are used but now now that we can cram a whole bunch of stuff into one little device you will find or you normally will find all of those logical devices are contained within one physical device so the modem the router the firewall the wireless access point and the switch are physically now one device now when we talk about in computer lingo they are all different devices they are logically different devices but they’ve all been built into one device so now there are one physical device so it’s hard to get a lot of people for them to get their head around but just remember that logical and physical are not necessarily the same thing so although you plug your computer into the same switch that everybody else is connected to you may not logically be part of that network and you may not be able to communicate with the other computers on that network the next thing we need to talk about is speed speed speed is is ridiculous what you should know that is data is is sized by two different types of measurement you can either have something called bits or you can have a bite so bits bits are signified by a lowercase B bytes are signified by an uppercase B so a Killough bit would be K lowercase B kilo byte would be K uppercase B what’s important is those two words sound very similar but it takes eight bits to equal one byte so a B equals one Big B so eight little bits equals one big bite now in the normal world when you were talking about storage when you were talking about how much data a harddrive can hold or a flash drive can hold or a CD can hold you’re talking about bytes so it’ll say megabytes are now gigabytes so you’ll see a hard drive that has you know 500 M B megabytes of storage well what the internet vendors do you know the Comcast’s the Verizon’s the quests of the world they they kind of mess with you because they know that you’re going to get confused when you buy internet service they tell you the speed in bits so if you have let’s say you’re with Comcast and you have a sophomore a second and you can download 12 megabit per second so that’s 12 Big M little B right that’s less than 2 megabytes I think it’s a yes 1 point 5 mega bytes because 8 bits are in a byte so if you’re looking at a hard drive and you’re thinking you know I want to upload 100 megabytes it’s going to take 8 times as long as you’re thinking because it takes 8 bit to make a byte so that that’s something that a lot of people get confused about but just keep that in the back of your head when you’re dealing with the internet or you’re transferring large amounts of data over the Internet is the Internet vendors tell you their speeds in bits data storage is in bytes and so it takes 8 bits to make one byte we’re now going to talk about the first device that connects your network to the Internet this device is called a modem so your modem can be for either a t1 connection it can be for a cable connection it can be for DSL or even be for a satellite interconnection internet connection any of these types of Internet connections require a modem to connect your network to to the Internet basically what the modem does is it turns your ethernet signal it turns the the protocol the language that you use on your internal network into the language that can be used on the internet so let’s say back in the day when you had the the old tile type modem in your computer used to hear that bird over well that sound was turning your data transmission it was turning your email or whatever you were trying to do into a signal that the telephone company could use so it turned the data into an audio signal the basic concept is true today so if you if you have a network that uses a DSL modem that the SL modem what happens is all the communications that are going out to the Internet hit that DSL modem the DSL modem then turns that that network communication into a language that Verizon or whatever your telephone company will understand and then that’s how it gets on the internet so the modem is the connector between the internet and and your network like I say there is a few types of different modems out there if you have a t1 connection you are most likely going to be using a device called an ad Tran a DTR AM this is something called a csu/dsu they’re not used a lot anymore just because T ones are very expensive but you know they’re there t ones are the best overall type of connection to the Internet but they are insanely expensive and today there they’re not very fast you can get something called T to s and T threes these are higher level T ones but they start getting stupidly expensive even now to in 2009 a t1 connection which is only 1.5 Meg’s per second is is about four to five hundred dollars you know compare that to Comcast Internet where for $200 a month you can get 50 Meg down 20 Meg up or verizon fios I think is the same for about 150 a month so the cost difference between a t1 line either FiOS or DSL or Comcast is huge but t1 lines do go farther so a lot of times if you cannot get DSL service in your area you cannot get cable internet or any of that a lot of times you will be able to get a t1 connection but just realize it’s going to be a lot more expensive the next type of connection is a DSL connection digital subscriber line these are provided by your phone company so if you’re with Verizon or Quest or any other other phone companies out there they will offer you a DSL connection DSL signals are generally very good and they come down in price so so here in Baltimore for about $15 a month you can get 756 K upload speed or download speed so it’s not incredibly fast but it’s fast enough for a lot of users what you should remember with DSL is dsls maximum speed is somewhere around 12 megabit per second it will never get faster than that it’s a it’s a problem or it’s a limitation of the technology so Comcast is always getting faster or cable modems are getting faster fiber optic modems are getting faster DSL will never be faster than 12 megabits per second it’s just a logical problem the nice part with DSM is that you have a solid connection between your modem and the central office and the telephone office where you connect to the internet unlike some of the other types of internet connections that share the bandwidth to a central place that gets on the internet you have a dedicated line between your house and Verizon so it doesn’t matter if a hundred people get on the internet or a million people get on the Internet at the exact same time you do you will never see a reduction service you know your your speed will not go down because all of your neighbors got on the internet at the same time that’s one of the good parts with DSL you should remember it’s DSL is asynchronous data transfer what this means is you you can download faster than you can upload so with DSL in our area you never are able to upload any more than 700 56 kilobits per second so it’s just something to think about most people this doesn’t matter unless you have a web server or if if you’re a business this may matter if people are using something called VPN to get into your network because then you will need to send data out to the Internet so this may be a problem so just remember you may have 8 megabits per second download speed but your upload speed will probably be only 756 kilobits per second the next type of connection is cable modem the cable modems have come a long way in the past 8 or 10 years they now are a lot more solid a lot more stable there’s a lot fewer problems using cable internet nowadays cable internet has introduced new technology called DOCSIS 3.0 that when it is fully implemented will allow for a hundred and sixty megabit per second download speed and I think it’s 80 megabit per second upload speed so technology that already exists has already been proven can give you speeds of up to 160 megabits per second download and like I say about 80 um at this point the cable companies are simply implement you know it’s just a cost thing it already exists they already know they can do it it’s not a huge issue doing it they just need enough money to do it the thing with the cable connections is unlike the DSL you do have to share that the main bandwidth that goes back to the internet so in some areas if a lot of people get on the Internet at the exact same time you can notice a massive reduction in speed so some days on my connection I get up to 20 megabits per second download speed and other days I only get 8 megabits per second download speed the reason is the more people that are sharing that that internet connection this is the slower the your access to the Internet may be there is also a satellite internet out there not a lot of people use this this is good if you’re just out in the middle of nowhere because you can literally be in the middle of a desert and you can get satellite internet the problem is the download speed isn’t too bad it’s about 1.5 megabits per second but the upload speed is absolutely atrocious you cannot do any type of real-time communication you can’t do voice over IP you can’t do anything like remote desktop you can’t do anything yeah that requires communication back and forth over the internet connection but if all you need to do is be able to webpages and download things off the internet satellite is out there they also have new wireless services the 4G networks you may have heard Oh from Sprint and now from Verizon these are starting to come into their own basically with these is you get a little wireless device that that connects to the cell towers of either Verizon or Sprint or whatever cell phone company in your area is providing the service so it’s just like if you had DSL or cable modem you hook one of these wireless modems into your neck work and then your network then connects to the internet through that wireless modem this is still a relatively new commercial technology so I can’t go into it a lot because it hasn’t really been tried and true tested in the real world but it is a possibility if you’re having issues right wiring and such you may use one of these wireless modems to connect your network out to the Internet so now that we understand modems the next device that under that is underneath a modem in your average network is something called a router so what the router does is the router allows you to separate different networks so let’s say you’re in a building and you’re sharing the internet connection between multiple different businesses in one building so sometimes you may become a tenant of a building and they offer you internet connection as part of the service well all of the tenants within the building may be sharing the same internet connection so they need some way to separate the different tenants onto their own private networks because you don’t want tenants hacking together you know you don’t want it all completely open so in that scenario what would happen is your internet connection would be split out from the modem and that would go to different routers for the different tenants within the building so every tenant would have their own router so what this allows to happen is each tenant no matter how many computers they have on their own internal network can go out through the router and go into the internet but they cannot get into one of the other people’s internal networks see you can go out through the router but you would not be able to loop and get back in and be able to hack anybody else’s network so routers are used to illogically to divide networks and this again is used normally for internet connections if you want to use only one internet connection but provide that internet connection to multiple users on multiple tenants on the network basically you would have one internet connection and then multiple routers connected so all of those networks can then connect to the internet without having to worry about anybody hacking them now underneath your router you normally have the firewall the firewall is a device that tries to prevent hackers from being able to get into your network through the internet firewalls are part of their own class they’re they’re part of a security function and nowadays especially they get very very complicated back in the old days they were their own standalone devices so underneath the router you would have a firewall and the firewall would try to prevent Internet traffic that you didn’t want to have happen so you didn’t want if you didn’t want anybody to get in from the outside world you would use a firewall and you would block like I say hackers from trying to get into your internal network from the outside world nowadays firewalls have become much more complicated and you can’t just say that they’re underneath the the router there’s software firewalls that are now built into each individual computer there’s their intrusion protection systems where you have entire servers that run a network of firewalls within your computer within your network so firewalls now are much more complicated than just a just a simple box thrown on the network but firewalls are a security device if you have a firewall it will nowadays it will be built into either your modem or into your router what you should remember is that if it is built into your modem or your router and you turn the firewall on if you’re using the firewall within the modem or router it will block Internet services for the entire network so if you don’t want people to be able to get on to websites for some reason they use something called port 80 so if you block port 80 in the firewall built into either the router or the modem then nobody on the entire network will be able to get to a website so firewalls are security devices if you use the one that is built into either your your modem or router remember that it will affect the entire network and may have some unintended consequences so but again this is part of a different class and so we’ll talk this more later so speaking about firewalls and keeping hackers and people that you want out of your network from getting into your network from the internet you may also need people from outside of your office to be able to get onto your local network most people use something called a VPN to do this a virtual private network what this allows is it allows computers that are anywhere in the world to connect to your internal network and as far as the computers and the networking devices are concerned that computer is now inside your network so if somebody is sitting in China and wants to print to your printer and Milwaukee they can connect to your network using VPN a virtual private network and then hit the print button and something will print out in the office in Milwaukee so somebody on a VPN can connect to all the shared files or folders share printers any resources that are shared on the internal network they will be able to access one thing to keep in mind though is they will be able to access it but a lot more slowly because your internal network works at at least 100 megabits per second which is pretty fast so but the person on the outside world remember they have to go through the internet so depending on what their internet speed is and what your internet speed is and any problems going on in the Internet right at that moment things can take a while things get very slow so like in my business I used to try to use QuickBooks through VPN through Virtual Private Network it was just too big it was too complicated of a program to work properly I could connect to it I could log in but the amount of data that needed to be transferred back and forth was just ridiculous so the VPN allows somebody from the outside world to connect to your internal network it does this through a what’s called a client-server architecture so you have a server inside your network this is a logical server it’s called a VPN endpoint so this endpoint has things like usernames and passwords of the people that are allowed to connect to the network using the p.m. Virtual Private Network then the client computer you normally install a little client application that can connect to that VPN endpoint you you give that client applications of information including your username and password it will then connect to the VPN end point it’ll authenticate and then as long as everything’s okay that VPN endpoint will then allow the computer to to be on the network so you have the client connects to the endpoint that gets you on the network why I now say that the VPN endpoint is a logical server is again back in the days there used to be things called radius servers or servers that all they did was allow people remote access to the network now for the most part this type of server service is built into another device so if you have a Windows server that has this service built into it you can simply turn it on you do not need an additional device to make this happen many of the commercial routers that you buy have this service built into them so they have a VPN service already built into them and if you go through your configuration routine you can just you can use that you don’t have to buy another another device another widget so Virtual Private Network allows people in the outside world to connect to your ends and be your internal network and it does so very securely so now after you have your your modem you have your router you have your firewall you have some of the other stuff that we’ve talked about now you come to the to the device that connects all of the devices on the network together to allow them to talk to each other this device is either called a hub or a switch hugs and switches are two different things if you have a hub on your network you need to pull it out and you need to throw it in the trash hubs are completely and utterly obsolete they were obsolete a decade ago they were obsolete back in 2000 if you still have one and you’re having networking problems if your network is slow it’s probably because you have a hub to see whether you have a hub or a switch you just look on the the front of it or on the top and it’ll tell you somewhere whether it’s a hub or a switch so on this switch if you can see that auto focus is see it’s a gigabit switch so a switch is something that you want a hug is not the difference between a hub and a switch is a hub is dump it has no intelligence whatsoever a switch has a little bit of intelligence and that little bit of intelligence makes a world of difference hubs basically split the internet signal or the network signal to everybody equally it is literally like a complicated cable splitter so you know you have a cable wire coming in your house you plug it into a splitter with you know three four or eight different connections and that runs two three four eight different TVs in your house that is what a hub does for computers the problem is this will go into another class because it gets complicated about how Ethernet and tcp/ip and all of that work the thing is that’s completely dumb and that causes problems now switches are smart they understand how to transfer data properly so that the network efficiently so basically what you really just need to know is if you have a hog we need to throw it out you want a switch if you want more information we’ll have a class on it so all the devices all the wired devices everything with a network cable at some point comes into your your switch now as you will see on the back of a switch it has ports basically the ports all the computers plug into these ports one of these ports goes to your router that’s what connects everything together switches I can have as few as four ports the average small business somebody probably like you what I have in my shop you can get switches with up to 48 ports so these are single devices they’re about yay big and they they can connect up to 48 computers if you’re in really great big enterprise a large company environments they have switches that will I mean just hundreds or a thousand users but those cost a hundred thousand dollars or more so I don’t think you’re going to be using those anytime soon so all of the all the connections to the to the computers and devices come into the switch and that’s how they all talk you will hear about what are called managed and unmanaged switches so as I told you hubs are completely done they they have no brain power they’re just there is that there is splitters the next level up is an unmanaged switch so an unmanaged switch has a little bit of brain power but everything is absolutely automatic in it so you can’t configure anything inside like this which you cannot configure anything you have to hope and pray that it’s doing what it’s supposed to do the next level up is something called a managed switch this gets complicated but like when you’re dealing with buildings or businesses that may be using 48 different computers the manage switch allows you to go to go into the switch and program the switch to do certain things again this gets complicated we’ll go into a different class but basically the manage which allows you to tune the network to make it work properly it allows you to play with things like quality of service and other high-level networking stuff that you don’t need to know about right now but basically the manager switch allows you to play and to change settings in the switch unmanaged switches don’t allow you to do that so the switch is what allows everything to connect together you as a small business or person will see switches either fork or all the way up to about 48 port they do have larger switches but again you probably will not see them because then you’re talking about $100,000 you will notice on the new switches it will say speed so there we go this one is 10 100 1000 so this is a gigabit connection networking has three speeds right now they had the 10 megabit connection speed this was about 20 years old at this point then they had the 100 megabit connection speed this is a speed that almost all networks run off of it’s just it’s been the standard or it was the standard for at least 10 years and now they have the gigabit on networking speed which is a thousand megabits per second this is the latest standard but your switch needs to be able to support the speed so if you really if you want the the fastest communication between all your computers on the network then you need to make sure your computer is capable of gigabit networking and then that your switch is capable of gigabit networking a lot of people now are buying these computers with really fast networking cards in them but then connecting them to the old switches and therefore the the speed of the switch will never be able to match this the speed of the computer so it will always be slower than it could be now that you have all of your wired devices talking to each other all of the computers on your network now talk to each other and then go out on the Internet now we need to deal with your wireless devices whether they’re wireless printers whether they’re your little iPhone or laptop computers those devices now need to be able to communicate with everything else on the network they do this through something called a wireless access point all a wireless access point is is it is a device that allows wireless computers and devices to connect to the network so it’s a device usually about this big some of them have a little Antanas on them some of them do not it doesn’t really matter as long as they’re wireless access point so those wireless access points all the computers wirelessly connect to them and then they will have one cable that goes from that wireless access point into the Swick and so that is how all of the device the wireless devices can then communicate with the wired devices and the wired devices can communicate with a wireless device through the wireless access point you will hear about four standards for wireless access points the first part of the standard is something called 802 11 this is just the the number of the standard you will then hear about a B G and n so eight 802 11 B a 2 – 11 G 802 11 n 802 11 a was a very fast very good standard that was pushed by Intel a few years ago and it did flopped it was technically it was fine technically was a fine standard just you know in the quirks of the business it gives did at 60 so if you see 802 11 a wireless networking devices don’t really worry about them because nobody really uses them and so don’t know try to buy them either if you see like 802 11 a wireless equipment cheap don’t run out and buy it because because you won’t be able to use it on anything a is not a Hannibal with any other type of the networking so G is compatible with B networks it is compatible with G and B networks B is compatible with B he and networks nobody is compatible with a it’s not a backward compatible or forward compatible standard so like I say a exists but it kind of died so if you see it it was a fine standard that died don’t really worry about it and unless you actually have it on your network the next standard is 802 11 B this is a standard that came out probably about 10 years ago at this point it’s been awhile it was 11 megabits per second um it wasn’t a bad wireless standard it was it was pretty slow we’re gonna have a lot of area but you know it wasn’t bad for the first standard so you have 802 11 B that was 11 megabits per second you then get went up to 802 11 G that came out probably about seven or eight years ago at this point that is up to 54 megabits per second and is a lot faster a lot more stable than B wireless networks and has been the standard now for you know since it came out at least six or seven years now so but B and G networks are compatible so if you have a B wireless card it can work on a G network if you have a G wireless card it can we’re going to be networked at this point though you shouldn’t have be around B B is old I mean it’s really old it’s something to know about but if you have it on your network if you’re using it just replace it throw it away and replace it because at this point it really is old the new standard is 802 11 in this just got ratified very very recently they’ve had something called pre n so the process to get standards implemented to get everybody to agree on a standard can take a long time to happen so a lot of companies come up with pre standards so what they do is they they look at what the current draft of this and it is before is actually accepted and then they create their devices around that so you will see there are a lot of devices out a few months ago that were pre in devices so what it was was the in standard had not been ratified so they created devices we’re pretty similar to the draft what you should remember now the end the standard has been ratified if you have these pre end devices then they may act a little quirky on the network because remember they were created before the standard was was finalized before it was completed so there might be some weird stuff in that that pre end device that you have or that pre a wireless access point that doesn’t make things on the network work well if I were you if I had the money and I had a pre end device I would probably try to get a new one because you could get weird problems like I say because it was created to a standard but the standard wasn’t finished yet and you know if you’re in the computer world I think you understand what that means now what is nice with the 802 11 in the standard is it allows for a much larger area to be covered by the wireless network so 802 11 and networks are twice as large as G networks they’re a lot faster than T networks I don’t know the exact number right now but it’s at least two times faster than G networks and the best thing about 802 11 in wireless networks is they allow for real-time video and voice communications how wireless networks worked in the past you would have a lot of problems with real-time communication so like voice over IP if you were using Skype or Google Talk or yahoo chat if you try to do that over a B or G wireless network a lot of times you get into weird problems simply because how the technology was built it was not built for real-time communications 802 11 n is built for real Communications and so that means we’re probably going to get a lot of really cool wireless devices brace it so what you should remember about wireless devices is you need a wireless access point the wireless access point that allows all the devices to connect to the network be key and in networking devices are all compatible with each other a is not don’t use a unless you it’s a legacy device that’s on your system otherwise don’t don’t even think about you know if it comes up really cheap don’t worry about it then the the BGN B is the slowest key is better in is the best that it is available right now and it gives you real-time voice video communication I want to take a moment to go into cabling most people don’t don’t think about cabling enough they they think of the cable that runs from their computer into the little jack in the wall and then that’s all I think about they don’t they don’t think about anything else so I’m going to take a little field trip in my store and show you how the cabling is run and what that what that means for the for your network so basically you have the cable that runs from your computer it then runs to the jack in the wall that gag has a cable maybe all the way up to 300 feet that then runs through the wall and runs through your building all the way down is something called a patch panel add the patch panel you then have another connector and that connector is what then gets plugged into the switch that we’ve talked about so let me let’s take a second and take a look around my store and show you what I’m talking about okay so it’s a little dark in here but as you can see this is the the normal network plug that you would plug your computer into so the the cable goes from your computer it will go in here then as you see on the bottom then there’s cable that comes out and this is what will run to the patch panel okay so now from that connection upstairs the cable runs down underneath the floor here you can see all the cables you can see see the cables coming together now here you see all the cables from the rest of the building so now we have about 15 cables that are all running down this one pipe and zip tied to it okay so now here we can see all the cables for the entire building come to this one area and they all get connected into the back of what is called a patch panel so the patch panel is this device right here all the cables get connected into it and then you use something called a patch cable so a cable that goes from the patch panel into the Swick so this is one of those big 48 pork switches I was talking about so this allows the computer upstairs to be connected into the port that’s upstairs that port has a cable that runs all the way down here runs into this patch panel and then from this patch panel you’re able to make the connection into the switch now you may wonder why you use something like a patch panel because it does cost money you know somebody has to install it yeah yeah yeah what the patch panel allows you to do is you know you’re going to be moving people around your building or the people might be in one location next year when they’re not there now so what you can do is you can run cabling to all the places that you might need a wired connection you can then connect those to the patch panel in your basement or wherever your server room is but you don’t actually have to connect them to the switch so think about this you can have in your building 200 network connections so they’re they’re all run if somebody needs a network connection they can plug into it but then you have a only a 48 ports which because you would only connect the network cables that need to be live at the moment so if your desk is here then you would make sure that that poor is live that port is connected to the switch at the patch panel well if you move your desk over here you might use a different network connection and then you would make that one live you would you would take the connection that was used over here down in the basement or your server room and then connect it to this other port on the patch panel so that’s why patch panels are used it makes everything nice neat orderly and you can run far more network connections than your using at the moment so like I say is you can run 200 network cables throughout your building and only use one 48 ports which because at any one moment you’re not using 200 connections you’re only using 48 so if somebody moves you can pull it out you know out of the patch panel and move it around but you don’t have to buy 200 ports of a switch that can get much more expensive now in this class we’ve been talking about network devices we’ve been talking about things like wireless access points switches routers firewalls modems we haven’t been talking about the normal computer stuff that you’re used to like computers in the networking world everything that is on the network is called a networking device so everything that’s on on the the network you know whether it’s a router whether it’s a voice over IP phone whether it’s a computer is a networking device you will hear the term clients and servers so in your business or your organization you probably have a server if nothing else you have something called a file server so you have one central computer that stores all the files that everybody accesses over the network so all a server is is it is a networked device that provides something to the rest of the network so if you have a print server this is a networked device that allows other computers to print through so if you have a shared printer then your computer is a print server if you have shared files then you have a file server so all the server is is it’s a device that provides services to two other computers on the network there is a difference and you should just remember those keep this in the back of your head there’s a difference between a server and a Windows server so a server again is a device that provides services for the network whatever it is any computer can be a server windows 98 computer can be a server Windows XP computer computer can be a server a windows small business server is a server then there are Windows servers Windows servers are a type of operating system that has been created by Microsoft so these are very specific types of operating systems that provide very specific functions that’s off in its own little world so a Windows server is a server but that’s not the only type of server that’s out basically fire site servers anything that provides services again clients then are any devices on the network that get services from a server so your computer you sit at if you send a print job to a printer that is shared on another computer you are a client of that computer if you access a file stored on another computer you are a client of that computer so the client is a computer or device that accesses something on another computer that’s all our clients and servers and devices are what they mean the one thing to remember though is is server there’s their servers in the computer world and then their servers in the Microsoft world and they are two different critters what you just remember servers in the computer world are any computers or devices that provide services to the rest of the network servers and the Microsoft Windows world is a Microsoft Windows Server 2003 2008 NT and they do very specific things so that was the introduction to networking class we’ve gone over a lot of the networking devices and I’m trying to explain to you how they tie in so that computers and devices on your network can talk to each other and then go out and get to the internet this is an interrupter e-class coming out of this you’re not going to know everything you’re not going to be a master of networking this this just gives you the basis so that we can delve deeper into the subject in the future we’ve gone over the basic concepts of speed the difference between the megabytes and megabits one byte equals eight bits keep that in mind we’ve gone over what is a logical them what is physical so physical is the actual devices the equipment that you pick up and it’s how things are physically connected this cable goes to that box logical is how it all actually works so many devices can be connected to one switch physically but inside that switch they may be logically divided up into different networks so all they know they connect to one switch they don’t necessarily are not able to communicate with each other so we’ve talked about modems they’re the devices that connect your local network to the Internet we talked about routers routers are used to separate different networks this is mainly used like I say in buildings with multiple tenants where they give you internet access so in order to separate those tenants so they don’t hack each other you would have different routers and that would separate the different networks out we talked a little bit about firewalls just a little bit because firewalls are big subject now and like I say they are no longer simply and only a networking device basically firewalls protect your network from being hacked beyond that it gets complicated you know either take another class here or learn more about it because firewalls get really complicated but they protect your network you then have the switch the switch is what all your networking devices connect into so every device connects into that switch and then they can talk to each other we talked a little bit about hubs as in if you have a hub throw it away because it is dark if you if you look at it if you if you look at the device and it says hub throw it in the trash simple that’s a troubleshooting technique if it’s a hub throw it in the trash by switch a switch is again there’s a either managed or unmanaged switches unmanaged switches are completely and utterly automatic there is nothing that you can do there’s nothing you can do with it you just plug it in and you hope it works manage switches you can go in and you can program them to do certain things again that gets complicated that’s another subject area but you should know that that some switches you can program them to do certain things and other switches you can so either managed or unmanaged switch we then talked about your wireless access points how there’s a BGN types of networks in is the best and it’s the newest the good for the best part about it is you can do real-time communications over it so you can do voice over IP you can use Skype Google Chat you can use digital surveillance systems you can do a lot of things on an in network that were you were not able to do before with BG networks a networks were fine for their time but it was not a standard that was ever picked up so don’t worry about a networks B and G they were good for their time now they’re now they’re gone I showed you a little bit about cabling so when you plug in that port in the wall there’s actually a cable that then runs all the way to wherever your server room is and plugs into the patch panel the patch panel is you then take a patch cord and plug in the Portland patch panel to the switch the reason you do this is so you don’t have to buy you know 300 ports which if you’re only using 24 ports because you can have more ports in your business or office space than you are actually using if you the patch panel we talked about client servers and devices so network devices is any device that is on the network whether it’s a router whether it’s a switch whether it’s an access point whether it’s an iPod whether it’s your computer whether it’s a print network printer that is a print device servers are any devices on the network that provide services to the rest of the network so a printer can have a print server built into it because if you plug a cable directly into the printer and then plug that into the wall other computing devices on the network can connect to that and print so a printer can be its own print device or you can have a printer plugged in to a computer and you can have that computer share the printer and that’s how the the printer is now shared so the computer is the print server because the the computer is allowing access to that printer clients clients are simply computers on the network that use a service from some server on the network whether they’re using a shared file somewhere whether they’re printing to a shared printer or whatever a client uses a service provided by somebody else servers their server like the big server name so servers in the computing world again are any computers that provide services to other computers on the network then there’s a Windows Server Microsoft Windows servers are specific types of operating systems that do very specific things so just remember servers are any computers on the network that provide service and then there’s Microsoft Windows servers that are their own little kettle of fish so that’s that’s the class on this I hope you understand what’s going on the the big thing to remember now is all these different devices we talked about we talked about routers we talking about firewalls we talked about switches we talked about VPN endpoints again that’s logically how it works now the devices that you buy have all these logical devices built into them physically so this router here is a router it’s a firewall it’s a VPN endpoint it’s a switch we connect up to four different computers or networking devices to it so this one physical device serves multiple logical functions so just keep that in mind so don’t like I say don’t don’t go up the store and try to look for a standalone firewall you you probably won’t find it all of the vices are now normally built in to one physical device so so again I’m Eli the computer guy this was introduction to networking and we’ll see you at the next class