Lecture - Networking

you you so today we're going to talk about networking ironically like I said we are having a networking issue in the classroom so we're going to try to make this a learning experience because you're going to come across this problem in the real world and you're going to have either your kids or yourself wondering what the hell's going on and you think the internet style well let's declare what is the Internet and how it might not be the internet being gown and might not even be your connection to the Internet but it might be something on your network so first of all what is a network well I got to get some new markers that works so what is a network a network is two or more devices connected together to share resources that definition has a lot of vague terminology two more devices what is a device this printer is considered a device it is a networked printer your PC is considered a device tablets laptops your television your blu-ray player all today are considered devices how do they connect together sometimes through a cable called the cat5 Ethernet cable sometimes via airwaves other times through coax said of calling it a connection we can to use it that's our use those as a term called a medium or media so what are resources resources could be files there could be currency they could be games it could be movies songs webpages Facebook status the point is is that we connect multiple devices together to share that printer is a resource on our network I bought one printer and I want to share with everybody our internet connection could be considered a resource so how do we make a network well the elements of a network this is the definition of a network the elements or components you're going to need at least a sender you're going to also somebody else to receive this remember two or more devices connected together so one device is going to be a sender the other device is going to be the receiver you you're going to need a message user that message is carried by a signal and then signal is going to be distributed or sent via medium because we have senders and receivers trying to pass messages to each other we too have some kind of rule or protocol that's going to govern the structure of the message the language of the message we take this for granted because in this country been indoctrinated into the English language so when we meet somebody we assume that they speak English so we talk in that language we make this giant assumption I don't ask you guys before I start class is there anybody in this class that doesn't speak English I make that assumption computers cannot make assumptions before they actually start transmitting messages to each other they have to agree on a protocol one of the most popular protocols you might have seen it it's called IP or ipv4 the I stands for Internet the P stands for protocol today we're going to explore what the IEP protocol dictates and how does it set up a method for transferring messages back and forth so network are two or more devices connected together share resources to create a network you're going to need a Fender slash receiver one being now that role will switch back and forth messages that could be the resource itself or the request for the resource the medium to carry the message as well as the protocols so what I like to do is create a topology you can think of topologies as being a blueprint of a network and we have two forms of topologies we have the physical topology and we have a logical topology the logical Baja chart apology basically gives you a illustration on how the network behaves for instance a ring topology one it could be like a circle and if I were to hook up a device now in computers terms sorry networking terms we call this a node you now that's only one device right do I have a network no let's get another device so now I have a network two or more devices connected together to share resources so let's call this node two we'll call this node one if node one wants to ask no - if they have a particular file it's asking for a resource it's going to send a message which direction would the message travel yet from 1 to 2 I was going to get there around the ring does it matter which direction it goes okay so it could either go this way or could go that way but eventually the message should get to that device correct hmm you let's put a note in here and let's put another one over here you now no one still wants to talk - no - remember it could go left or right this is just the logical behavior let's just say when no one and anyone goes to talk around this ring traffic will flow in a clockwise fashion think about those roundabouts like we have a roundabout out here at the center of our entrance connect Corning do you see how traffic there's only one lane there so we got to make sure that traffic all follows that direction doesn't matter if people are going left or right but as long as they're all going in that same general direction correct could you imagine some decides to go opposite direction as everybody else is going around that roundabout what's going to happen an accident and networking we call that a collision okay so no two devices on the same medium can send and receive at the same time clear about that so think about sending/receiving as going in opposite directions so when node one wants to talk to know to what's going to happen with the other communication going on this network it's going to stop they're going to listen in fact how does node four or three know that it's their time to talk how do you know it's your time to merge into that roundabout traffic in this center of our entrance web when there's enough room to fit your car in front of somebody without pissing them off correct so there's some kind of visual cue in this network that visual cue is known as a token in fact we typically call us a token ring you can think of it as a microphone or a mail cart in a corporate office it gets passed from desk to desk to desk right now no one has the microphone and it wants to communicate with no.2 in order to get there its first going to go to node 4 no.4 gets the message but the message is not assigned to so we have this is coming from node one and it's going to know to note 4 does not have the address that matches this destination in other words you get the mail carts being passed around you open you get see what's inside of it and says this is addressed to Mitch if you're not Mitch what are you going to do with the letter pass it on note 4 is not no 2 so it's going to pass the message on you see this little relay going on from device to device the important thing the thing that should concern yourself is maybe security node 4 decides to not open it up will make that determination is this protocol it's a set of rules and in there it's going to say if the destination IP address of this message does not match your address ignore it in fact we get into a physical address if you will coin case in point is the message is now being touched by node 4 determines not that pass it on - no - no - gets the message what is it going to do so this tokens being passed around no to sees that this message was destined to no - that's me what would you do if a message came by and had your name on it open it up in the meantime none of these other devices can communicate with each other even if no three want to have a conversation with node one that wasn't going to happen why not the only time you're allowed to communicate in this network is when you have the microphone the token where's the token at right now at no.2 this is a logical behavior why do we do it this way why do we have roundabouts verse stop signs verse traffic lights verse intersections without any kind of control and that's the key here this is called media control you what do you guys prefer intersex without any control traffic lights over stop signs over roundabouts over in Europe there they're all about the roundabouts in this country we're all about the intersections with stop signs or traffic lights let's talk about it which one's more effective no control stop signs traffic lights are roundabouts traffic lights traffic lights almost like this when you have the green light you can go when you have the red light you can stop so traffic lights are good for like large volumes correct but it's one o'clock in the morning on Dennison Highway nobody's around and I have a red light and I'm waiting and waiting and waiting and waiting for it to go green yeah exactly especially near the dump or not now what about stop signs everybody has to stop right but it's like a one out of turn so it's like four seconds go I know it's just people are rude so what about roundabouts how does roundabouts work there yields so if there's nobody there if you keep on going correct and if there's somebody in the circle then you have to stop or at least slow down so they get ahead of you the idea in a roundabout you keep your traffic going moving the problem is that people always try to think they have to right away when they're the one trying to merge into it Oh in the cities they get really horrible because there's more traffic right so this what I'm trying to say the more users we have on the network what's going to happen the number of messages we have the more chances of an accident correct we want to try to avoid that why do we want to try to avoid these collisions think about it when there's an accident downtown and then busy intersection what is that about what does that mean about your travelling experience delayed and that's what happens to your network the more users you have on your network the greater the chance that you're going to have collisions the greater chance you have a collision the or performance becomes right this is one method to handle it we say look shut up until you have the microphone and what does that mean about collisions as long as everybody's following the protocols zero collisions right that means large amounts of data can be distributed that's one philosophy this is at the logical layout it's not actually wired this way it just allows us to understand that if you're at this point and you want to talk to this one you're going to go in this direction then you're going to be going through stopping at these points and they're going to be checking the information out as another way of killing it you we'll call this a bus certain Network terminology is called a multiple multi access topology I like multi access topologies a lot better than calling it a bus but nevertheless it's still the same thing in general you you there is a common medium here it's this backbone by the way this is the way coax television works and if you have broadband from Time Warner this is going to be a similar technique and how they manage it generally in these typologies they implement something called CSMA / CD the CD is at collision detection and any one of these nodes can communicate at any time but before they go to communicate they check the medium to see if there's a carrier the signal that carries the message if there is no signal then it's safe to do what and this is not the way we communicate in this classroom if you will what is this carrier or what is the medium in this classroom what do you and I use to transmit back and forth can't do it in space no movie made in late 70s from there movie poster used to say you can't screen space or nobody can hear you scream in space and the physics behind that is there's no air in space there's no air not that you can't breathe is that you can't transmit does look how we talk suck in a bunch of air you vibrate your vocal cords the air comes out in the your mouth as a message now as a signal your eardrum detects the varying pressures that your vocal is created correct well there's no air to breathe in to carry the message then you can't talk so we use air to communicate each other and when the air is silent or dead what does that mean you can go this is your opportunity if it's quiet what can you do huh right and that's what happens here what's cool about that is it doesn't go around in here if this person doesn't have anything to say they're going to get the microphone and then they have to pass it you can talk when you want to talk as long as nobody is using the medium that makes sense now what happens from time to time like 1 1 & 3 want to bail talk and they both check the medium to see if this signal is available it happens in this classroom you waiting's dead air it's your opportunity to answer once again this is the protocol that we have to establish most you guys don't raise your hand something you do and I call on that the racing the hands like a token but here under saying well if I'm not talking it's your opportunity to talk and what if both of you are more than one of you if you will wants to say something you listen the air is dead and you both transmit and then there's a collision correct how do you know there's a collision because while you're talking you can also listen right we call that full duplex in this network we have school duplex well let's not do that oh I'll modify it we have half duplex and the reason why I modify it is because the next apology I'll say we have folded less if full duplex allows you to talk to listen at the same time that half duplex means like CB radios you push the button to talk you let go the button to listen we get about that I say this is half duplex because if three is transmitting - choo-choo is listening nobody else can talk right now likewise while I'm talking you guys are listening and nobody else should be talking because it can be disruptive now if there's a collision and two people are talking at the same time whether you detect it or somebody else is going to detect it they're going to make it a big announcement like I did a meeting on Tuesday shut up right that's called jamming signal so like I said this type of topology using something called CS ma / CD carrier sense multiple access I am more than one nodes accessing the same medium collision detection this one doesn't try to prevent collisions it just says look Nick if it's one o'clock in the morning and nobody's around and you checked both ways go ahead and cross the red light you should I worry about a collision if there's nobody around for miles it's one o'clock in the morning I do have a red light the protocol says to me stop wait to go green there's type of technology saying well look nobody's using it go ahead and cross so we don't avoid collisions we just build the protocols to accept them and communicate and if there is a collision try to clear out the wires obviously the more people on this network slower becomes this one scales really nice because there's no collisions so we can have a lot of people on large geographical distances here small graphical distances smaller sets of people so what do we do to make the best one whoops nuts that start so you guys are thinking something like this right remember these are all logical topologies I'm using them as tools to illustrate how the message travels or behaves on these types of networks the center of a star topology is going to be a switch and rating out from that switch are going to be notes you you you these are like points to a star between the switch and the node we have what we call a logical point-to-point Network point-to-point it's actually point-to-point protocol to to pppp I mean three P's and let me do that so I don't get point-to-point protocol what does that mean if this is the only device or devices connected what does that mean about collisions it's only you and somebody else there shouldn't be any right if you're just going out with a friend and you're having a conversation they talk you listen they stop you talk they listen right if it's more than two then you might have a problem because now you might want to talk but the other person wants to talk to so you got to worry about collision so here we don't have collisions we love these types of networks because we gain what we call full duplex why because the switch acts like a Waystation it's like Grand Central Station everything comes and goes to the switch the switch has a big buffer it builds it up when this port becomes available or when this node is able to listen this switch will pass the message through so you send everything to this Center device and it distributes it for you this is like back in the day when we didn't have traffic lights or stop signs and we had traffic cops and they would stand in the middle and they would wait people on and they were smart enough to detect when there was going to be a collision if you will here we drop it all in here and this which passes it around star topology supports full duplex the nice thing about stark apologies and this is the way you typically wire your home networks you want to add another device to your network you simply plug it into a free port and hook it up to your computer done on this network you have to crack or cut the line when you cut that line it brings the whole network down because at the end of these we have we call terminators to let them know that the signal doesn't propagate too far out remember the signal is constantly going through these wires so we got to terminate the signals in order to add to this we got to cut the network bring it down add the device and come up this becomes a problem with troubleshooting you don't know where the problem might be on the wire so you got to use some fancy tool to try to narrow it down then splice it and the problem of fixing it bring the whole network down here if this computers experiencing problem and no other computers are experiencing problem I might just check the cable between here there the port or just that computer but about something like this if it goes down right there is communication loss what if we just switch directions it's communication still lost when you send something you better get a message back can we send the message back because we have to travel in this direction if we're using half duplex that is if the medium that we're using only allows it to go one way and we decide to switch it and pass it this way I can't back it up that way but wait a minute nobody should be talking while I'm trying to have a conversation with this device so yes it's called a sonic ring and we can bounce it back now if this happens the only people that can have a conversation is 1 & 3 & 2 & 4 that makes sense where are these typologies used Connect cities together Connect homes together maybe depending a few years in coax and cable-tv connect homes connect local devices now folks this is just a general overview of course it gets more technical than what you're seeing now but this is just a literacy course you don't have to be experts in networking but I want to make sure that you understand that each of these topologies have their own way of managing the message okay I like to start small like to start at our house remember we're experiencing some technical problems and we need to try to narrow it down this classroom is an example of a star network in fact this classroom is called a local area network short for a land once again we're back to a generic word what do we mean by local if I ask you is anybody local to Corning what do I mean by that you you live in the corning area so if I show you this classrooms example of a local area network what do I reference what am I trying to specify here but everything is close together if it is very small geographical location to scope this classroom is one local area network the classroom behind this wall is another local area network it becomes tricky on how we define it one aspect is a local area network is governed or controlled or ministered by a single organization your home would typically be a single local area network and you're responsible for the devices that connect to your network okay geographical space or size let's compare your home network to a corporation or even to this classroom then you would have more than 18 devices on their home network we have 18 devices if not more here in this classroom now you go to compare to a big corporation they might have thousands of computers it's a local very tricky I like to define it as it's a small network organized by a single individual organization that have a common interest goal or resources case in point we meet in this classroom to talk about 1390 so this class in a sense is like a local area network we want to exchange ideas resources people are networks you guys are our device on the device we are connected together by air you have some knowledge I have knowledge we share that that's definition of a network when I define a local area network I'm focusing on the Ethernet standard a lot of people call this an Ethernet cable we're going to give it a better name in a minute the ethernet standard dictates the type of interface we will use to get on to the network in fact that has a better name it's called a network interface card the Ethernet standard also states that we're going to be using IP addresses to identify each node hence it basically says as a sub bullet no two devices on the same network can add the same IP address why would that be a problem why would it be a problem that two devices on the same network at the same IP address bless you when we send messages to devices we use IP addresses to identify them so there are two devices on the same network that have the same ip address the device is responsible for relaying the message around well know which one to send it through do you mean NIC or do you mean Nick so hence all devices have to be unique this is a good area to troubleshoot one you need to make sure that your devices on your network has an IP address if it doesn't have an IP address then how am I supposed to send you something if you don't have a name or mailing address second these IP addresses are going to have something known as a network address and a host address so it has two parts you can think of it as your name you have a first name and a last name your last name for the most part is shared with other people in your family correct does that sort of identify your group well on an IP address certain parts of the address is shared by other devices to help define well local area network is what else does it define the type of medium that's going to be used why does this become important when you guys buy a USB flash drive are you worried about it not plugging into your computer why not why aren't you worried when you buy a USB flash drive that it will not plug into your computer the fact that it says USB flash drive if I tell you if you buy a thunderbolt flash drive should you then be worried so that's why we say you need to have an Ethernet card you need to have an Ethernet cable and you can have an Ethernet switch they all begin with the word Ethernet so they should be compliance and Ethernet comes in many different flavors or speeds we have 10 base T 100 base TX a thousand base I believes T is low what are they referring to you seen that before right folks capital M what is that typically mean mega right lowercase B what does that mean be careful lowercase what's that Mitch bits this is where your telephone or your internet service provider get you all the time because what's bigger bits or bytes in other words what's going to take when you write on a piece of paper how many bits make up a letter nice will review eight right which we call a byte so when you compare one byte to eight bits you think it's a bigger number correct so this gives you a larger number but when you go to compare it to bytes technically be smaller translation this is about one megabyte per second if you have a five megabyte song it would take you five seconds to transfer this file okay this is about ten megabytes per seconds therefore this would be about a hundred I'm just dividing by ten because I put the eight and rounded it up you guys get the general philosophy here so be careful of that so with the PS that it's not PostScript per second so we are measuring literally how fast it takes bits to travel through this particular network local networks have huge amounts of bandwidth now you have to be careful bandwidth is three sort of classifications you have what we call the normal or theoretical bandwidth the thorough put and a good put Marketing people use the biggest number of that that would be the theoretical bandwidth you will never obtain the theoretical bandwidth never it's like the miles per gallon in a car if it says 35 your pond never going to get 35 right so then you got this Thoreau put the data plus the overhead because I have to send address information plus other things to tell the network how to handle this package I called it a message earlier now I'm calling it a packet a pack is just a little sliver of the message so the good bandwidth of the good thorough put is just how fast the date of the stuff that you care about is transferred and it's usually about 80% 70 to 80 percent of whatever your actual bandwidth this okay so if you are having time warner's your broadband company by the way other factors in Paris to write number of users but if they're your bandwidth your broadband company they sell you out 10 megabit per second just multiply that by 80% and that's about give or take what you should expect it yet okay so to build this local area network I'm going to need a switch a switch is an intermediary device that handles local traffic they give us full duplex and they negate collisions you're going to need either twisted-pair ethernet cable as you guys are commonly referred to and a network interface card on your end device your switch has ports I remember two more devices connected together you these interface cards are the ones that get IP addresses you you how do I know they're on the same network because they're connected by this device here they're in the same physical network because they're using a switch since I'm using the ethernet standard I'm using at least cat5 twisted-pair cable you can think of this as just glorified telephone cable if I were to cut this open and you expose the pairs for you what you would see is a bunch of wires wrapped around each other hence the word twisted now they come as pairs why the biggest hurdle in offering consumers broadband in this country is the distances we're a very wide country I think we're about 3,500 miles wide anytime you deal with length and physical properties you're going to get resistance it's like putting your car in neutral and rolling down the hill without starting it up or doing anything adventure your car will come to a stop correct you have the resistance the internal resistance plus the external resistance likewise here this is a copper cable what does copper carry very well and why do we use it what do computers use quite a bit how do we manipulate data and computers electricity right so when I go to transmit the message from computer to computer over this twisted-pair cable I'm going to be using electricity and as with anything there's going to be resistance in here and it's also going to be interference because when you run electricity over a copper wire you are going to generate what we call Electrify and EMF electromagnetic field let your magnetic it's electromagnet right what do magnets use whether they love what attracts them to the other they align North and South Poles right so basically if you will the polarity or the electrons on one material is being grabbed by the other material by the other magnet fluffs what carries electricity electrons so therefore we can say that our electrons are carrying our message right so if I am sending voltage this way through this cable I'm generating a magnetic field that goes around here's the issue that magnetic field is going to be messing around with the other pairs we alright with that hence it causes interference to negate this interference we take the opposite direction the sending pair and so it's pointing in this direction we wrap the magnetic field around there and they cancel each other out this cables very cheap because of that we're not adding layers of insulation or aluminum foil to protect it we're just taking two copper wires wrapping around each other and send electricity opposite directions economical it's great for running it in your house it's like maybe a cent a foot if you buy it involved extremely fast very dependable very safe not as safe as fiber but safer than airwaves but yes folks you do have to run the wires to connect your devices to your switch what do we do when we don't want to do that though what do you guys go and buy a wireless router now you'll notice that all wireless routers become integrated that is they take the switch and they integrate it into that device you can look in the back of your wireless router you'll see a bunch of ports and even that's all good with that in fact we recall this it's 802 dot you 802 dot is the Ethernet standard then you guys have 11 it might be a B G and and now we're up to AC and what are they telling me why using those letters a B G and a C which one is better a or AC or an orgy they tell you distances and that's important you're in Wi-Fi right you want to know how far you can travel in your house just like a dog testing his boundary when he's on a leash and the other thing that becomes a point is if you are starting to distribute high-definition content across your local area network you need bandwidth out of those B is the slowest then we go to GA I always go between G and a because a uses a 5 gigahertz spectrum and G uses a 2.4 gu zé's a very common spectrum hence a lot of interference a doesn't but it uses a sensitive frequency so it's a gift take relationship so I always like ranked a and G depending on your environment the same so what about N and AC and can handle bandwidth up to about three hundreds this is not counting multiple outs about three hundred megabits per second okay a she is one gigabit per second Wireless it's a new standard I think it was released last June I think it's like three hundred dollars for the router and a hundred dollars for the interface card right now but if you're distributing high-definition content across your wireless network or you're trying to share resources between your neighbors computers and they're in another building AC is the way to go it's a lot more powerful how do you know this just go to store look at the router box flip it over they'll tell you what the transmission rates are okay the point is this is an Ethernet wireless router that means this wireless router can hook to my switch which means it's compliant with our network which also means if I have a laptop what am i up to node3 connected via the airwaves what must that laptop have Wi-Fi part interface card and that interface card must have what you you all of these notes must have a similar IP address but you can have the same IP address right what do I mean by similar IP address when you go to set the properties of ipv4 your computer's going to ask for the nodes address I'm just going to do the standard you guys seen that number before when you've had to set up your wireless router and your house like a 192.168.1 or maybe one ninety two dot one sixty eight dot 254 or something to the effect and then there's going to be another number I'll just start off with one an ipv4 address is 32 bits translation it contains four parts right what's 32 divided by four eight right how many bits are in a byte get into connection now each of these parts are eight bits now what's 2 raise to 8 I always been a while what do you need to know these numbers can only go from 0 to 255 per each of those when you are configuring a computer and you say well you know what let's use 368 it's not going to work your operating system will yell at you because each of these octet will only allow you to enter a number from 0 to 255 and for most part 0 and 255 are reserved so technically you go from 1 to 254 clear about that so when you go to set an IP address up on your network make sure it's within this range don't care what it is you could say that I want one got 2.3.4 and i will check this is where the protocol comes in that each of these are cats are between 0 and 255 is it all right the next thing how do I determine if this computer's IP address is 1.2.3.4 what do I make this computer's IP address should I do two dot 2.3.4 because the next number after one is what how does somebody know I have one of those unfortunate names where my first name and my last my last name could be a first name right how does somebody know that's my last name and not my first how do we identify that you what usually comes first in professionally printed documents I change it in the phone book right last name first and phone book but like when you write a letter here you might put a mister in there or if you're going to spell out the full name what comes first first name right and it's the word first name okay when it comes to an IP address our computers need to know what we call a subnet mask usually specified by default you guys seen that before when you're typing in an IP address and one your devices you say you just click on the subnet mask box and automatically puts them like the 255 this is what you need to know as far as what determines this this is the network address how do you know that what did appear underneath each of those are cats each of those numbers 255 s right so I'm saying any number with the 255 underneath it is part of the network address we okay you so what's this part then we call it the host that's what needs to be unique so when I go to give this computer an IP address it needs to be 1.2.3 because they're part of the same local area network right so if they're paws the same physical network they also need to be the same logical network now what can I not give this computer for because 4 is used by the other computer correct so let's give it a 5 now let me give this computer an IP address 1 2 3 . resisting an IP address you does anybody secured their wireless routers how'd you do that okay how'd you set the password did you open up a web browser and in the address bar did you type in the IP address of your wireless router unless it came with the CD which would have done the same thing for you okay I know that smarter the newer wireless routers are becoming smaller but they should get an IP address it's going to have dual functions if you will notice I gave it a 1 now I said it's going to have dual function this is it this is a network everybody has an IP address no two devices on the same network have the same IP address they are all connected together through some medium whether it's twisted pair or Wireless and they're using the same standard can I expect a lot from this network not really the only thing I can expect to share on this network whatever local files I have stored or local resources if I add a printer I can share that as long as that printer has an ethernet card and I properly configure it so that no two devices have the same IP address it can be shared hmm what else could I share on this network know what maybe I want to take one of my older computers and make it into a server I'm going to make it into a server it's going to need an IP address so I'm going to give it one dot 2.3.3 what does that serve we're going to do from it I know I'm a home user and I'm getting a little carried away but my biggest problem is that I have a bunch of files scattered all over my network so-and-so has pictures so if they'll have the videos of the family picnic if their computer crashes I lose those memories unless they decided to back it up on their own external hard drive or a flash drive but how often do we back up our files we don't so if I had a server or some external network area storage device that does that I can set this server to backup all my devices on my network at a certain time if these computers are stationary if I'm downstairs in the living room and I want to check a particular file out whether it's my taxes or great papers or whatever and then all of a sudden I want to go upstairs because the weather is nice and I want to look outside the window by having all my files stored in a centrally located area wherever I go in my house I should be able to access them translation the server is running all the time and they give the people to share resources and what we call a client-server relationship something you guys are familiar with using the web correct this technology is going to be implemented in your household I don't believe you guys will be having full-blown computers I think you might buy one massive computer if you will and that these nodes are simply going to be monitors that allow you to talk and touch that gives your i/o right all the processing all the storage will be done here what does that mean as far as growth scalability yeah I'd be concerned about putting all my Easter eggs in one basket but if it's just here all I have to do is get a new monitor or new keyboard I can keep on adding to the network low cost especially if it's a Wi-Fi network so my question is how do I make this network be able to do more share more or have access to more resources what must we do and why must we do this you it's not a requirement yet but it sure is a necessity can't live without or an accessory if I want this network if you will to share more resources or have access to more resources what must I do remember it's a local area network local to my house it can only share resources that are contained within my house if you guys want to go to California what must you do get off your ass jump in your car and do what leave your driveway and connect to an interconnected highway system that we call the interstates correct now do you pay every time you get on that road not per mile but your taxes pay for that road correct so what you're saying is we need a pathway the and Nexus to a bunch of other networks oops around the world and that's what we call the internet the interconnected networks or networks of networks they probably have switches and offer their switches they probably have little devices oops this is called a wide area network you see just get some wider and wider and if I want to talk to sell and sell over here my message will first go to my router depending on what type of connection I have to my what's the word I'm looking for three letters your ISP your eye is people I connect to other ISPs what we call NSPS network service providers so this is just one example of how a wide area network is just a sliver of the whole internet so we have a router that serves the purpose of being able to pass messages out of our network onto other networks another word for your router is called a gateway it's like the door to this classroom this is a local area network that hallway is a wide area network why what does that hallway do what does it connect other classrooms and didn't I say the other classrooms would represent their own networks and so somewhere on those other networks is a resource that I'm looking for whether it be Google whether it be Yahoo or Amazon and so my message now travels from my network to all these other networks until it finds its final destination what does that mean about all the devices that are connected together what should they have what have we learned when we create a network they all must have IP addresses what is the I stand for an IP internet right all of these devices must have an IP address my question is at home if you guys told me that you're using 192.168.1.1 how can I use that what's this yes this is a local area network and it's protected if you will by my ISP in fact when you probably order broadband to your house by the way I'm not talking about dial-up even though they follow a similar nature probably get a modem familiar with it's usually black box that your cable comes into or your telephone line comes into and all the modem is is short for modulate demodulate translation folks we got these signals right now the type of signal is traveling through this is the ethernet signal but now I need to switch it over to my cable company right they use coax which is going to use a different type of signal and it's going to have a different way of modulating the message so that I have to have a modem to basically modulate the do different ways sort of acting like a bridge to connect the two if you will so the router serves two purpose it's designed to protect your network like a door in your house because your door in your house hasn't locked correct your router will have what we call a firewall and also beam at it this becomes very critical because we are getting to the point where we have stuff at home that we want to be able to access from anywhere and around the world or our firewall is designed to close up ports connections coming and going from our computer if we haven't ignition it the conversation then nothing come in through that hole if you will so the firewall basically inspects the packets that are coming and going and if we haven't asked for that packet in other words if you're not invited to my party what's my front door man going to do turn you right around cuz you're not on the list that's the firewall what about NAT network address translation it takes your private IP addresses and converts it into a single public IP address when you order a monthly subscription from your ISP they give you a public IP address let's say I hope I'm not even one let me use two and that's going to be on this side of your wireless router folks when you buy your wireless routers with the figure M you notice in the back there are certain ports that are identified uniquely it used to be called the wind port what's it called now thank God they did this usually you'll have four ports to plug in for wired network for Wired devices but then you'll have one special port got a little globe on it the internet port right that's support you would hook up your modem to you good about that that port is literally the gateway out of your network so when these other computers want to talk to you on your network they use this external IP address your public IP address okay then it comes to that router that router looks at it and says oh yeah so-and-so made that request you see this point you as a client make the request Google just doesn't go pounding on your door saying here you want this no you must first type in a domain name and your web browser by doing that you make a request a wait a minute I said in order to pass messages around we use IP addresses but when we type in to our computer our atari more importantly into our web browser we type in numbers now we type in domains we've learned about domains right in all the different parts of it so how does the computer use the name to communicate on the network that requires numbers by the way this is the problem that we're having in our lab today it's called DNS domain name services this is what we're going to do together as a class taking this theory and making it practical because I needed to cover these components so that we can look at the physical world and narrow down what's causing our issue first thing if you walk into a building or in a room and you try flipping the switch and the lights don't come on what's going through your mind build this troubleshooting method do you have a blown light that's a possibility right what else could be a possibility okay what could cause the power to be out storm you can pay your bill an accident what's in your control though anything that's local correct so what you might do is look across the road and see if your neighbors have power if their lights are on right what does that rule out somebody hit a pole or the storm knocked out the power unless they have a generator so be very thorough knock on your neighbor's door and say you guys have power if yes are you running a generator all right no so that means I know at least we have power going up our road now do you inconvenience your neighbor before you do your own system check so you flip on the switch nothing's going on maybe go to another room what do you do there nothing comes on what are you thinking now all right so first step you go to a computer on your network you check internally doesn't work jump off that computer go to another computer doesn't work now you wanna check your circuit panel now these are little black switches they flip sometimes automatically if there's a surge so check to see if they're all flipped on they are now what's the problem what's the next thing you're going to check if the circuit panel is working none of the lights come on in your house you guys gonna be faced with this right what are you going to do now you didn't pay your bill maybe your transformer out and your poles blown but that's beyond the stuff that you could have checked correct so let's do this I want everybody hold your window key and hit the letter R type in CMD you guys are you guys faced with a black screen with white text this is called your command prompt remember when we were learning operating systems I said something along the lines that we have a graphical user interface and we also have a command-line interface I love using the command line interface the troubleshoot networks the first thing we check is the self we call this a local aside a loopback hang I want you guys to type in P ing space 127.0.0.1 now I probably got a little ahead of myself and I probably should had you guys check something before you do that but when you guys do that I'm just trying to get my monitor up not able to find it oh check the cable back behind it all right so you guys have this screen right here right so when you held the window key and hit the are you typed in CMD and then hit enter this screen pops up like I said this is your command prompt the first thing we're going to do is we're going to ping our loopback so I'm going to type in P ing space 127.0.0.1 what do I test or what am i testing when I do this pink your operating system goes through you the user interacts with the operating system and it interact with the software so the software has to interact with the hardware right so we have this stack these seven layers that the message has to go through this think of them as like little checklists if you will what the loopback does is it just checks to see if this stack is functioning properly I haven't even left a computer at this point so if this loopback fails there's something wrong with this and you have to reinstall your network driver okay that address works for everybody one 27.0 0.1 what's on all devices that have an ethernet part okay you know it worked because you get a reply from okay you see the time it took to get back to you is less than a millisecond because all you're saying is self are you still there so you're going down through the stack check and to make sure the protocols are functioning the next thing you need to do is ping your IP address how do you know what your IP address is well we have a command it's called IP ironically config or conveniently so all one board type in ipconfig and hit enter it's going to list all the interfaces on your computer that have an IP address you see we have an IP address v4 of one ninety two dot one sixty eight dot one then dot something everybody else has a number there we all have Dan you're saying now oh yeah I'm getting to the point this calls in the issue I am working up the ladder but those were able login I one ninety two dot one sixty eight dot one then some number afterward right nobody in his classroom chef two twenty good about that you notice you have the subnet mask of 255 255 255 dot zero I know that everybody in this classroom who has that subnet mask will have the first three ayah octet of the IP address the same good about that and then everybody in this class has a 192 dot 168 got one got one for the Gateway no interesting what do you have Josh nothing hmm you can use the computer we can communicate with each other but what can't you guys do alright but some of you guys don't what is the gateway it's the way out you don't have a door and you're in a room that's what you can't you leave that room right so we might have some issues with connectivity but let's ping ourselves so let's ping our IP address of one ninety two dot one sixty eight dot one dot two twenty or whatever your address is what that test is your interface card and the cable connected to it now I don't I like to rule that cable connect to it because in a minute we're going to ping your neighbors did you guys get all replies for all those that could do this good pin your neighbor find out what their IP addresses is I'm going to give me an IP address the nessa which is two one eight I said Vanessa gave me her dress now what am I doing here I'm testing to see if I can connect to my switch and her connection to the switch is good because this network connects all these local devices together so if I get replies which I do I have local connectivity correct so step one loop back step two ping your IP address step 3 ping your neighbor's IP address you guys are the same IP address what have we learn though two devices on the same network can have the same IP address so therefore that's probably why even get a gateway address because if it was automatically assigned they didn't know who should get that address so we have a conflict there because we have duplication next thing I'm going to ping my gateway address so I'm going to ping one ninety two dot one sixty eight dot one dot one what a thing does is it sends the message to the device to the door and then it comes back to me if I get replies if I don't get replies yes what's going to happen I have a problem between my switch in my router DCL is like an all-or-nothing test alright I'm able to communicate with my gateway I like this so far so good everything's working now you could ping an external computer a computer on another network let's see I don't know what their IP address is but what I do know might be their domain name so I'm going to ping Google so I ping www em and I hit enter and if taken a lot longer than it did before right and it's going to fail what does the computer need what does the ping command need at this moment in order to communicate with Google Google's IP address right what service on our network is responsible for taking a domain name and resolving it into an IP address ENS my DNS server is doubt you see it's a server what have we learned about servers many people connect to it you see we all had a problem earlier logging into these computers because we're all logging into the same server so when I try this a matress server now I want you guys to open up your web browser and I want you guys to type in the following IP address type in 173 dot 190 4.40 3.14 and tell me if Google's for you won't work for you guys these guys are not the Gateway Johnny if Google's web page comes up so open up Firefox or Chrome and type in 173 dot 190 4.40 3.14 did who will come up it should have what happened is I said let's not use the service and let's dial the number directly right I'm able to get right to it so that tells me as a technician I'm having a problem with my DNS at this moment if this was your house you would call your ISP up and saying there's something wrong with my domain name services it's on them ok folks so we'll finish this up on Tuesday you guys have a good weekend ah powerpoint assignments and posted on my IG lab we're only doing two parts of access ok guys you guys take care and I will see you on Tuesday

Channel: Nicholas Andre

Views: 151,576

Rating: 4.9155846 out of 5

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Id: kNKHM_isojI

Length: 81min 52sec (4912 seconds)

Published: Wed Apr 17 2013