Module 4 - Understanding Network Services

7. 4.6 DNS

I don't know about you, but for me it's a lot easier to remember the name of a destination on the Internet as opposed to the address of a destination on the Internet. For example, if I want to go to my website at Kwtrain.com, I don't know what the IP address is, but routers need to know that they route based on IP address information, not based on names. So we've got to have some translator that sits in the middle that says, oh, the IP address corresponding to tKwtrain.com or wherever you're going is this IP address. In this example, the desktop computer wants to go to the web server, and we're going to pretend that the web server is@kwtrain.com, and the desktop computer does not know that the web server's IP address is two, 30, 113, 100. It just knows that it wants to go to Kwtrain.com. But it does know the IP address of a DNS server. It knows that there is an ADNS server available at 192 0210.How does it know that? Maybe we manually configured that on the computer, or maybe it learned it via DHCP when it first booted up and got its IP address information. But somehow, that desktop computer knows how to get to the DNS server, but it does not know how to get to Kwtrain.com. So it's going to ask the DNS server, "Hey,can you tell me the IP address for Kwtrain.com?" It sends a message to that DNS server using port 53, which is what DNS uses, and it's asking if you can give me the IP address for Kwtrain.com? And the server responds and says yes, that has an IP address of 2030, 113, 100. And the desktop computer says: awesome. Thank you very much. And then it's going to send its message to the web server. And if we're going to a website that's non-secured, that's going to be port 80, or if it is secured and we're using HTTPS, that port is going to be four, four, three. But the web server is going to respond and it's going to say, "Here is the web page that you requested." So the desktop computer, just knowing the name of the web server, was able to reach it thanks to the translation performed by the DNS server and the name of that web server on the Internet of Kwtrain.com. Or maybe it's FTP Kwtrain.com for an FTP server, if I had one of those. Those addresses are called FQDNs, or fully qualified domain names, and the worldwideDNS structure is hierarchical. Here's what I mean. We start at the root. There is a root domain and there are twelve differentcompanies roughly around the world that take care of pointing us to DNS servers that know how to get usto.com addresses, mil addresses, and so on. These are just a few examples of top-level domains, or TLDs.com is a popular one. And these are some that we have in the United States. In other countries, their top-level domain might be a two-letter abbreviation for their country. For example, the United Kingdom might have a UK as its top-level domain, and under each top-level domain we have second-level domains. Again, just a very few examples. We might have Amazon.com as the second level domain and Amazon.com as the top level domain. And we, as the DNS administrator of our company, for example, Kwtrain.com, could go in and we could say, "I want to define certain subdomains within my second level domain." For example, consider Purdue.edu, and I'm just making this up, but let's pretend they have a couple of subdomains of CSN: Business, maybe different colleges within the university, CS for computer science. So it might be CS Perdue.edu or Business Perdue.edu. Those are subdomains. And let's say within the computer science department, they have a worldwide web server and an FTP server. So we could put the actual host name in front of those subdomains and we could have an address for a server, something like www CS perdue.edu.And although we've already discussed several DNS terms in this video, I've got a few more for you that I really want you to know. So you might want to take some notes on these. First up is an authoritative name server. Remember when we had those top-level domains like.com pointing down to a second-level domain? Well, the main server in charge of that second-level domain is called an authoritative name server. Take my website, for example. kwtrain.com TLD,the top-level domain, points down to the primary server of Kwtrain.com. That's my authoritative name server. And I may just have one primary DNS server for Kwtrain.com or maybe I've got an additional one if I've got a secondary one. When there is an update to the primary, we need to replicate that change over to the secondary. And that process of transferring information is called a DNS zone transfer. What typically happens is we've got an update on the primary DNS server and it's going to send a notification to the secondary DNS server saying, hey, I just wanted to let you know we've had a change. And then, typically the secondary DNS server will say, okay, give me that information, and that's a zone transfer. And the way we've described DNS thus far is I'm providing a known fully qualified domain name and FQDN, and in return from the DNS server, I'd love to get an IP address. However, there are times when we're looking at different services, for example, that we might want to provide an IP address and have returned to us the fully qualified domain name ordomain names associated with an IP address. That's possible with a reverse look up.And finally, consider an internal DNS server and an external DNS server. We may want to have a server that's acting as the DNS server for clients within our organization, not on the Internet, and we might have another name server and external DNS server that is going to resolve queries that come in from the Internet. And these internal and external DNS servers may have different DNS records. Maybe there's a DNS record for the internal DNS server that's not available to the external DNS server. If somebody is on the Internet and they want to get to that inside resource, and they have to query the inside DNS server to do that,is that possible if someone is working from home? Actually, it might be. An employee might be able to set up a VPN secured connection coming into the organization, and at that point they would be able to query the internal DNS server and connect to private internal resources,even if they're working from home. As an example, And as we're entering DNS information while configuringour second level domain, we're going to be tracking different types of DNS records. Let's take a look at those. The most common type that I think of is an A record. This is an address record, and this is the record that translates a fully qualified domainname into a corresponding IP version for an address. For example, when we talked about Kwtrain.com and talked about its corresponding IPV-4 address, well, that was possible due to an A record. What about IP version six? Well, we also have an IP version of the sixaddress record, but it's an AAA record type. There's also a canonical name or a CNAME record type. This is another name for an existing record. Maybe we've already got an A record for Kwtrain.com, but we wanted to go by another name as well, like Kevinwallacetraining.com. Well, we could have a CNAME record that's analias of Kwtrain.com, and within Kwtrain.com, we have emailaccounts, and we could have an MX record to point to mail servers for our domain. A pointer record or a PTR record that works hand in hand with a CNAME record And it's often used when performing a reverse DNS lookup. So with the reverse DNS lookup,instead of saying "here's the fully qualified domain name," what's the IP address? We say, "Here's the IP address." What's the corresponding fully qualified domain name? an SOA. Record or start of authority? Record This gives us some good information or documentation about this site. It tells us, for example, things like the email address of the administrator. We can see which server is the primary name server for this domain. We can get information about different types of timers that might be configured. So think of an SOA record as sort of an informational record. There's also a text record or a TXT record. And the original intent for this record type was to contain some descriptive text that we as humans could read. But more recently, it's been used to carry attributes that have meaning to the computer that requested the information. It's more generic. A service locator record or an SRV record that's somewhat similar to that MX record we talked about for email service, except it's more generic. It can point to hosts providing a variety of services,while the MX record is used just for email. And finally, you can specify, optionally, an NS ora name server record that tells the DNS zone to use, for security purposes, specific name servers. And that's a look at DNS, the translator between fully qualified domain names and IP addresses.

8. 4.7 NAT

Some bad news about IPV four addressing: we're out. You cannot go to your country's numbering authority and ask for a block of addresses. You will not get it because the IPV4 address base has been depleted. However, we're still adding networks all the time and networks are being assigned IP versions for addressing. How is that possible? Well, a common approach is to use private IP addresses inside of an organisation or inside of your home and then translate those private addresses to publicly routable addresses. Remember that we have some private address space in IPV Four. It's Called RFC 118 Addressing We've got the ten-address space and the 170 216 through 172 31. We've got 192 168. All those are private IP address spaces that can not be routed on the public Internet. But we can route them just fine within our network. What we want to do is take a private ipaddress and translate it into a publicly routable IP address. And the way we do that is by using a service called Nat Nat Network Address Translation. And in this video, we're going to take a look at a few different variants of Nat. First of all, let's assume that we do have a pool of addresses and that we're able to use those addresses to route on the public Internet. And we want to translate our private addresses like ten one and ten One One Two.Like you see on screen, We want to translate those into publicly routable addresses. Well, the first thing we need to consider when we're setting up Nat is to decide which interface of the router is considered to be the inside and which is considered to be the outside. That's important. And we're going to say in this example,router R One's inside interface is Gigabit and its outside interface is Gig Two.And let's say Client One wants to go to this Web server. Well, if we take a look at the IP packet, it's going to have a source IP address of ten One One.And the destination IP address is the IP address of that Web server, 2030 113 100. However, router R One is going to take that source IP address of Ten One One,which cannot be routed on the public Internet. And it's going to translate that into an address that it picks from this pool of publicly routable addresses that it has. Let's assume that R One has the luxury of these 99 addresses. It can select from 109 20219, all the way through 109 20219 Nine.So it's going to pick one of those addresses and that's going to be the new source address when this packet is routed out of the public Internet. The source IP address is now 109 20210 One.And if Client Two wants to go to that Web server, yeah, it's IP address. Its source IP address is going to be tenOneOneTwo, and it's going to be translated into a different publicly routable IP address. In this case, 109 (202-2102).Now, when the return traffic comes back, how does the router know that this packet goes to client one and this packet goes to client two? Well, router R1 is constructing an internal net translation table. Like we see here, We say that if we receive a packet coming from the Internet destined for 109 202-2101, we know that translates into client one at ten to one. If I receive a packet destined for 109, 20210, two Based on this table, we're going to send that to client two at ten one one two.And that's a basic overview of how Nat works. But I need you to know some terminology. And this terminology can get really confusing when it comes to Nat because there are different types of Nat addresses. We have four. We have inside local, inside global,outside local, and outside global addresses. Let's go through some examples here. First, consider the private IP addresses that are being used by clients one and two. We say those are inside local addresses. Here's the way I want you to look at this. Look at that first word inside or outside. If it says inside, then it's referring to a device on the inside of our network. These clients, in this example, and local means, are addressed locally by Rabble just within our organization, or is it globally by Rabble out on the public Internet? Well, ten to one is an example. It represents a device on the inside of our network, client One, and it is not routable on the public Internet. It's only locally routable. So that's an inside local address. When R One translates those inside local addresses into addresses that can be routed on the public Internet, what are they called? And this is where a lot of people get confused. Those addresses are called inside global addresses. And the confusion comes when people look at this and say, "Whoa, hold on." These addresses are on the outside of the network. But remember, the criterion for having that first word be inside or outside. If that first word is inside, it refers to a device on the inside of our network. So let me ask you, what does 192-02-2101 refer to? It refers to client 1, a device on the inside of our network. So this is an inside address. It is globally routable. So that makes it an inside global address. Now we're destined for that Web server at 2030 113 10. That is a publicly available address. It's on the outside of our network. So that would be an outside global address, meaning that it points to a device on the outside of our network and globally,meaning that this address is publicly routable. But there's one we didn't mention here, and that is outside local. You'll probably never run across an outside local address because that would be referring to a device on the outside of your network that was only locally routable. About the only time you might ever come across that is when you have a couple of corporate sites separated by maybe the Internet. And there is private IP addressing at that remote site. From your perspective, it's now outside of your network. It's at this remote site, but it's an address that can only be routed locally within their site. How can you even get to it? There's a lot of configuration that goes into it. You've got to set up some DNS configuration. You've got to do some mapping. It's not something you're going to want to do because there are better ways of doing that. So I really just want you to know that these three types of addresses inside local refer to devices on the inside of our network, but the IP address is only locally routable. Inside Global is still referring to a device on the inside of the network, but now it's globally routable. It's the address that we were translated into. And outside Global, that's maybe our destination on the Internet. It's outside of our network, and it's a globally routable address. Now, in this example, we could have statically configured this. We could say, I always want ten to be translated into 109 (2022). That would be an example of static NAT. Or in this case, I said picked from a pool of addresses. We dynamically selected an address that's called dynamic Nat. But those are not the most common types of NAT because, commonly, our Internet service provider doesn't give us a pool of addresses. They gave us one address. Think about your home network. You have one address assigned to whatever you have on your cable modem, for example. And you might have lots and lots of devices on the inside of your network. How can they all share that single, publicly routable address? And the answer is, they're going to use a variant of Nat called Pat, which is port address translation. In this case, we have a router enabled for forwarded address translation and it has one and only one publicly written IP address assigned to it. 192, 2, 1, ZeroZero That's the IP address given to it by its Internet service provider. And everybody on the inside of the network needs to share that address. So the paradox is, how do I keep all these different conversations separate? How do I know that this packet goes to client one and this packet goes to client two? And the answer is, we keep track of more than just IP addresses in that Nat translation table. We keep track of port numbers. Remember that when client one wants to connect to a Web server, we'll say it's a secure Web server, so port four four three is used. So the destination is 2030, 113, dot 100. Using port four four three, client one has to pick a return port for itself. We might call that a dynamic port, or we might call it an ephemeral port. And in this case, client one picked port number 49,525. And normally, the pad enabled router will keep that same ephemeral port number as it goes out to the web server. So notice the source IP address as the router sends it to the web server. The source IP address is now 192.02.10 because that's the only publicly routable IP address we have. But we have that ephemeral port number. Some of the traffic comes back to us. We're going to be able to know that this goes to client one because we kept track of that port number. That's why it's called port address translation. What if client two wants to go to that same web server? Well, it's going to probably pick a different ephemeral port number. We're going to have to share the same publicly written address because we've only got one, and it's one hundred and ninety-two, zero, two, one hundred. And sure enough, client two picked a different ephemeral port number: 52,142. Now, yes, it is possible that the two clients would pick the same ephemeral port number. If that happens, the patent enabled router is smart enough to know that it happened, and it's going to assign a different ephemeral port number and it's going to keep track of that in the Nat translation table. So we've expanded the Nat translation table a bit here with Pat. Now we're keeping track of not just IP addresses, we're keeping track of port numbers. And that's how we can have lots of devices on the inside of our network share a single publicly routable IP address. And I want you to know about one other implementation of Nat that you might not realise is Nat. You might hear it called "aport forwarding" or "port mapping." That's Nat in reverse, sort of. Here's what I mean. Let's say that we've got a remote client out on the Internet. It's IP addresses are 2030, 113, and two ZeroZero, and it wants to get to a secure shell server inside of our network. Maybe we've got a Linux server running SSH and we want to connect to it remotely. But we've only got that one publicly routeable IP address on our 11920 2100.How can we come up with that one and only one publicly routable IP address and somehow get connected to that secure shell server? Well, we can set up a port mapping that says if somebody comes in to ZeroZero and they come in on port 22, that's the well-known port for secure shell, then we can set up a static NAT entry in router R one to say, oh, that needs to go over to ten one one two. So this is kind of like Nat in reverse, isn't it? Now we're translating an incoming connection to a specific device on the inside of our network. So that's a look at network address translation. It's how we continue to use the IP version for addressing even though we're out of these big blocks of addresses. We took a look at some different variants. We said we could have static Nat, meaning that this inside local address is always mapped to this inside global address. We talked about Dynamicnet, where we could pick an inside global address from a pool of addresses. And we talked about port address translation orpat, where we have only one publicly routable IP address, but we keep all of our connections identified based on the ephemeral port numbers that are being used by our inside devices. And then we took a look at sort of a reverse implementation of that, which is sometimes called port mapping or port forwarding.

9. 4.8 NTP

My favourite saying about time is that a man with one watch always knows what time it is. A man with two watches is never quite sure. Well, for our network devices, we want to have one watch. We want to agree on what time it is. And that's possible thanks to a protocol called the INTERNET TIME PROTOCOL. And before discussing how it works, let's think about why network devices need accurate time. Well, as just a couple of examples, if we're doing troubleshooting and we're going through logs of our network devices,we can see what time certain things happen. Maybe at 02:00 a.m., this server experienced this error, and at 01:59 a.m., this router gave this error message. And if everybody agrees on what time it is,then we can do some event correlation and maybe narrow down the source of the problem. Also, for security reasons, we can use digital certificates to make sure that we're talking with the party we think we're talking with, and to make sure we can communicate with them securely by encrypting traffic. These digital certificates, though, have expiration dates. At a certain date and time, a specific certificate is no longer valid. So we need to agree on what time it is. If we don't have our clock properly synchronized,we might think it's a different year. We might think an invalid digital certificate is invalid or a valid digital certificate is invalid. And those are just a couple of reasons why Another reason that comes to mind is if I'm working on an IP phone, a lot of times those IP phones will display time, and they get that time from a server that gets its time via NTP. Well, in the United States, the naval observatory is the keeper and reiterate of the time. And they both have atomic clocks in Washington, DC. and Colorado Springs, Colorado. And the way an atomic clock keeps time is by monitoring the number of vibrations or oscillations of a cesium 133 element, because cesium 133 will vibrate a little bit over 9 billion times per second. And after that, many oscillations occurred. Dingding, ding. That equals 1 second. So this is a hyper-accurate clock. Now, we are probably not going to be able to point to an atomic clock from our computer,but there are lots of other NTP servers on the internet that can point to that atomic clock. So what we're probably going to do is have at least one device in our network, like a router, point to that clock, which may be getting its time from an atomic clock, and we're going to synchronise that time for router r one.In this example, using NTP, NTPuses UDP ports one, two, and three. And here's a memory aid for you if you want to memorise that port number. I think of the old Jackson fivesong ABC easy as one two three. Well, I think of NTP as one, two,three, and NTP also has a mechanism that gives us the believability of a time source. Now, the most believable time source is that atomic clock. And believability is measured as a stratum number. And the atomic clock has a stratum number of zero. And the stratum numbers can be zero through 15 and still be valid. If we get to 16, then that source is considered not to be credible. And let's say that we're pointing to a clock on the Internet that has a stratum value of one. If it has a stratum value of one, that means it learned its time from one of those atomic clocks with a stratum value of zero. because we increment the stratum value by one each time we go from one time source to the next time source. So if our router R One is going to be the time source for our network and it's going to hand out time and it's learning from a stratum one clock, you guessit, it's going to have a stratum value of two. So now R One is a stratum at 02:00 and it can hand out time throughout the network. Or if we have somebody within the network that's going to hand out time and it learns time from ROne, it's going to have a stratum value of three. But instead of having lots of devices within our network going out to the Internet and saying hey, what time is it? They can just ask R one.And R One is going to propagate time throughout the network. And that's a look at a way that we can have an authoritative time source in our network. And that's thanks to the protocol of NTP.

10. 4.9 SDN

In this video, we're going to discuss technology that is largely redefining the role of a network administrator. When I first got into networking, the way we would configure routers and switches, and we can still do this,is we would go to the console of that router or switch, or we could secure or telenet to it, and we could type in a bunch of commands from the CLI, the command line interface. However, that doesn't scale very well if we need to make lots of changes to lots of devices. Let's say, for example, that we have an e-commerce company and we're running one of those really expensive advertisements for the big game, and we expect that after the big game commercial airs, we're going to be flooded with lots and lots of traffic coming just inundating our web servers. So we decided to spin up some extra virtual machines to handle that load. And we want to reconfigure the load balancer to spread the load across those different virtual machines. We want to reconfigure the quality of service and want to prioritise the e-commerce traffic coming in to make sure all those orders go through. And then, after a few hours, maybe we want to go back to our normal configuration. That's a lot to do manually, but SDN is going to allow us to programmatically configure our network devices. And to better understand SDN, let's take a look at how networks traditionally work with routers and switches being configured one at a time. There are three different operational planes for these routers and switches. There's a data plane, there's a control plane, and there is a management plane. Let's talk about each one. The management plane that's in charge of allowing us to access for management purposes that router or that switch. As an example, the management plane might run a protocol such as secure shell to allow us to connect to the CLI remotely. The control plane is in charge of runningprotocols used by routing protocols, or on aswitch, maybe it's the spanning tree protocol. For example, OSPF might be running on the routers you see on screen. Well, that process of running OSPF and running the Dick extra algorithm that OSPF uses, that's all happening at the control plane. And the control plane is populating the routing table that is going to be used to make forwarding decisions. And the data plane is concerned with data. When a packet comes in, its job is to figure out where to send it, and it's going to consult the IP routing table or maybe the Mac address table on a switch to determine how to afford that traffic appropriately. And this traditional approach is called a distributed control plane because the control plane exists on each of our devices. However, with SDN, we may have an SDN controller, and the SDN controller can take care of control plane tasks. It can run the docker algorithm for OSPF, and it can run the spanning tree protocol calculation. It can populate the Mac address table and the IP routing tables because it now contains the control plane. And the way it does that is by communicating with these devices through what it calls an API, an application programming interface. And the way we normally draw this is with the SDN controller in the middle and the devices that are managed at the bottom. You can think of these devices as being south of the SDN controller if you think of a compass where south is down. So we say that these APIs, these application programming interfaces that are pointing down to the devices, we say they are southbound interfaces, which we abbreviate as SBIs. And in this configuration, where the SDN controller is doing the control plane work for all the different devices and communicating via southbound interfaces, this is called a centralised control plane because the control plane is now centralised in that SDN controller. Most SDN controllers aren't going to be using telnet or secure shell or simplenetwork management protocol to communicate with these devices. They're going to be using some sort of SDN protocol such as OpenFlow. That's one of the standards-based Southbound interfaces. So if the devices were managed south of the controller, what we have living to the north are applications. These are programmes that perhaps we write or maybe we modify someone else's code to meet our specific needs. And these applications are going to communicate with the SDN controller through northbound interfaces, or NBI for short. Because the applications are typically drawn above the controller, They're north of the controller, but they're not going to be using things like OpenFlow. They're going to be using what are called RestAPIs, or some people call them Restful APIs. The rest stands for representational. state transfer Here's what that means: It means we're using the same sort of messages that are used with a web server. If we go out to a web server and we pull down information, we might be using an HTTP verb of Get. Or if we send information to a web server, we might use a put or a post HTTP verb. Those same verbs are used between the applications and the SDN controller to pull information from the controller or to send information to the controller. I could send my intent to configure all three devices at the bottom of the screen for some sort of quality of service configuration, I could send my Intent.This is why it's called "intent-based networking." I can send my intent using this application down to the SDN controller and it's going to know, based on my intent, the appropriate Southbound API messages to send to the switch and to each of the routers. Because quality of service configuration commands may be different between the switch and the routers, the controller knows what to send to specific devices. And I mentioned that these applications could be programmes that we have. If we do that, the most popular programming language for SDN software-defined networking is Python. And when we send a rest message down to the SD controller saying "Can you give me this information whichit may glean from the devices down below?" Or I want you to send out this information. That request is sent by the appropriateHttp verb or Restful API. It needs to be formatted in a specific way, and there are two popular ways of encoding the data in that message. One is called JSON, which stands for JavaScript Object Notation, and that's the one we will probably see most often. The other option, which you might see, is XML, which stands for Extensible Markup Language. But that's an overview of software defined networking, which is really redefining what it means to be a network administrator. Because we're moving from a world where we configure one device at a time to one where we express our intent for the network configuration inside of an application, which communicates with the controller, which sends appropriate instructions down to the devices, and that lets us dramatically scale the size of our network and how quickly we configure that network.

11. 4.10 IoT

One of the buzzwords in the industry you hear a lot is IoT, or internet of things. And what the internet of things is implying is that it's no longer just computers that might sit on our desktops that will connect to the internet. We've got lots of different devices that might connect to the internet, such as the thermostat in your home, or maybe a door lock or video camera for security around your premises. In fact, a few years ago, the number of IoT devices exceeded the number of non-IoT devices I'm thinking about in my own home. My wife and I each have a few computers, but we have lots more IoT devices. We've got lots of light bulbs that come on at specific times. Those are connected using IoT technology. We've got about three thermostats and a couple of doorbells. We've got about ten video cameras. We've got lots of IoT devices, even in our appliances. Our refrigerator is an IoT device. If we leave the door open too long, it sends a message to my watch, and it sends a message to the TV saying the door is open. Things are starting to become more and more interconnected, and that's our focus in this video. First, let's answer the question: what is driving this very fundamental change in networking? Well, one thing is how widely available high-speed internet connections are. No longer are we limited to those slow dial-up modems. It's very common to have high-speed connectivity within our homes. And we have more and more devices that have WiFi built right into them, such as those light bulbs I was telling you about. And since a lot of these devices are controlled by the smartphone, the growing adoption of smartphones has led to the increase of IoT devices. And just as a few sample applications where you might see IoT devices,one might be in predictive maintenance. My daughter used to have a car, and I would receive emails from it on a regular basis if it needed maintenance. If she had low tyre pressure, I would receive an email informing me that the pressure in her left front tyre had dropped to a certain level. You might want to put some air in it. You might also see this used in an assembly line in a factory. Maybe. We have different assembly lines and one assembly line breaks down. Well, those devices can automatically detect thatinterruption and redirect materials to be sent to another assembly line to minimise the impact of that assembly line outage. It could be used for automated inventory management. And an example that comes to mind here is Heineken. They have a monitor in a keg of beer that they send to a bar. And that monitor can check the amount of beer remaining in the keg, and it can check the freshness of that beer, and it can send a message back to Heineken to make sure that there's a fresh batch of beer at the bar before they ever run out. And we've already mentioned that some home automationapplications, such as controlling lighting around your home,controlling the environment with a thermostat, controlling securitywith different video cameras and doorbells, are also heavily used in health monitoring. As an example, you might have a smartwatch and if it detects that your heartbeat is out of a certain rhythm or at a certain rate, it can send you an alert about that. And I really want you to understand some of the underlying technologies that make IoT possible. And the first one is Zwave. Zwave is often used for home automation. As an example, Honeywell has some thermostats that use Zwave, and Zwave can communicate. In a mesh topology, all the devices don't have to be connected back to a central hub. They could be, but in a mesh topology, one Zwave device could send its data to the next Zwave device, and it could send that to a nearby Zwave device. So everybody doesn't necessarily have to connect back to a hub. And something important to know about Zwave technology is that it uses radio waves in the 900 MHz band. That's not going to interfere with your WiFi networks, which operate in the two, four, and or five GHz bands. And sort of a competitor to Zwave is Zigbee. Zigbee is also used for home automation. It's not compatible with Zwave. And on the positive side, Zigbee is faster than Zwave. It can accommodate more devices in the network, it can do more meshing, you can go through more hops than you can with Zwave, and it can operate in the 900 MHz band,but it can also operate in the two 4 GHz bands. So be aware that if you do that, zigbeemight interfere with some of your Wi-Fi communications. An ant and an ant plus Those are low power standards. They do operate in the two Gbaht bands. You might see these in mobile devices such as heart rate monitors that you can wear. You've probably heard of that one. That's going to be a fairly short-range technology, and it will use fairly low power. And you can connect multiple devices together using Bluetooth. For example, if I'm away from a WiFi network and I have my laptop and I want to get on the Internet,I can use Bluetooth to tether my laptop computer to my cell phone, which is then going to use five G to get out to the rest of the world. I use Bluetooth on a daily basis to connect my speakers to my computer. If you're in a checkout line at a grocery store,you might be using NFC, or near-field communication. Some smartphones have NFC capabilities where you can hold your smartphone up within just a few centimetres, like 4 CM from the checkout device. And it's going to pay for what you're purchasing. A technology that has been around a long time is infrared, or IR. You see this frequently with TV remote controls. It is a line of sight. It's not going to interfere with your WiFi networks, but it's not going to go around corners, it's not going to go through walls. It's a direct line of sight. So it's fairly short range, fairly low throughput. Another example of infrared is I've seen it used to print, where you could print from a laptop to a printer using infrared technologies. RFID is very popular. That's radio frequency identification. And you can have either passive or active RFID tags on different things. As one example, one of my friends works for Lexmark,the printer company, and he was telling me about paper that you can put in their Lexmark printers and can have an RFID tag embedded in that paper. Maybe in a lawyer's office. You want to make sure that nobody takes a sensitive document out of the office. Or you can have these RFIDtags on each of these documents. So somebody could very quickly scan a file folder and realise all the documents are there. Or if somebody tries to take a document outside of the office, once they go through a portal like a doorway, it can alert someone that somebody is taking this piece of paper with an RFID tag and they're trying to leave the building. And that's with passive RFID. And that's a fairly short range. You can get a longer range if you power an RFID chip. And one of the most popular supporting technologies out there is the WiFi communication that we use on our laptops or smartphones to get on the network. There are different IEEE 800 and 211 standards. There are 800 and 211. A, B, and G. Also, N and AC. And at the time of this recording, the newest one was sometimes called WiFi Six, and that's 800 and 211 Ax. And there are a tonne of IoT devices that use 800 and 211 technologies. For example, in my home we have thermostats for doorbells, TVs, arranged lights, and the refrigerator. They're all connected to the WiFi network. Now, something to keep in mind with IoT technologies. I've noticed that when they connect to a WiFi network using some 800 and 211 standards, they almost always use the two 4's instead of the 5. So if you have a WiFi network and you have a name on your WiFi network, which is called an SSID, let's say it's called Kevin's Net, if it's operating in both ranges,that could cause a problem with your IoT devices. They might attempt to connect to an access point that advertises that the SSID in the 5 in the IoT device is only compatible with a 2.4. So what I've done in my home is set up a separate SSID, or in other words,a separate WiFi network just for IoT devices. And it's running at two of 4 GHz only. Now there are some IoT devices that can work in either range, but I've noticed that there are predominantly IoT devices in my home anyway. They exclusively use the 2.4. That's a look at IoT, or the internet of things.

ExamSnap's CompTIA N10-008 Practice Test Questions and Exam Dumps, study guide, and video training course are complicated in premium bundle. The Exam Updated are monitored by Industry Leading IT Trainers with over 15 years of experience, CompTIA N10-008 Exam Dumps and Practice Test Questions cover all the Exam Objectives to make sure you pass your exam easily.