 Welcome back. This is the second part of our lecture on location management. In this lecture, we will try to figure out how in some cases the identity of a particular entity can be mapped to its location. So, last time we had a look at MAC addresses and IP addresses. We will just quickly have a look at what they were. So, MAC addresses are something that comes in built from the manufacturer and IP addresses are something that are assigned by a system when a device connects to the network. The MAC address is actually a constant for a device. You know, it ideally should never change. However, we talked about that it can be spoofed at the software level. The IP addresses may actually change from network to network. So, if a device connects to a different network, it may be given a different IP address. And even on the same network, if it is reconnect, it is possible that the IP address may change. The duplicate MAC addresses may cause some problems on the network. You know, they can probably cause some havoc at the lower levels of routers and switches and all that stuff. But in general, the network will still probably continue to work. In case of duplicate IP addresses though, the system will take an action and then it will kick out either all the erring entities or it will simply keep one entity and you know kick out the others. So, basically at the end, only one entity with one IP address will be able to sustain itself on network and others will be kicked out. So, that is why IP addresses are almost always unique. In fact, always unique on the network. Now, we are going to talk about identity that can be mapped to location. So, we have already talked about what identities are in the previous lectures and we talked about what addresses are. Now, we are going to have a look at how in some cases, these addresses can actually be translated to locations. So, we will just have a review of something that we called location of wired devices. We talked about something called a library computer or say workstation 10 in the ground floor. We said that if a computer is connected to a LAN cable and that LAN socket is say you know in library or something, we can actually fix the location of the computer because of the fact that it is a wired device. We still did not say anything about exactly how can a particular LAN socket be mapped to an address or you know how can just by having look at a particular devices IP address or some other address, how can we say this is the device which is the library computer or the workstation. So, now we are going to have a look at this. So, whenever a device connects to a network, if the network somehow enforces a rule that it will always be given a particular address, then we can have some kind of a mapping between device and address. We are still not talking about location, but we can somehow fix a mapping between device and IP address. So, let us take an example of the library computer that we were talking about. Let us just say any computer which connects to the network from the library is given the IP address say 172.27.18.33. So, once we are able to somehow enforce this rule, we are pretty much sure that any device with this particular IP address on my network is in library because I have enforced a rule. Any device connecting to library will get this particular IP address. So, on my network, all I need to check is if any device is having this address, I am pretty much sure that it is the library computer only because I have somehow enforced a ruling. We have not yet talked about how that enforcement can be done. Let us just assume that there is some way I can enforce a particular IP address on a particular LAN socket, but basically there are techniques available to do that. So, if I can somehow ensure that the library socket any device connecting to that will get the same IP address. In future, whenever I see that IP address on my network, I am pretty much sure that it is the device connecting from library. The next thing is mapping these addresses to geo locations. So, we had a talk about how I can probably fix a particular IP address to a socket. So, if that particular socket is being used by any device, I can clearly say that that particular device is actually connecting from that particular location. Now, this mapping need not just be at a very micro level. Right now, we just talked about locations within a say an institute or something. These can actually be done at a much, much higher level as well. So, we can do these things on city level, on state level. They can actually be done on any level we want. So, we just saw how a particular IP address could be mapped to a location if we somehow enforce this rule in the network, but that solution is not very neat. Because we need to define these mappings at a very micro level. We have got to figure out addresses for all the LAN sockets in my institute probably and then I could be sure that any device connecting to that LAN socket will get this particular IP address and with the help of this IP address, I will be able to identify the device. But this mapping is not very neat. But what we can probably do is, we can have it have some kind of both ways. We can try to do little bit of mapping and then leave the things dynamically as well. So, we will come back to this, but before that what we are going to do is, we will have a look at. So, we saw that if an address is attached to a location somehow, then we can actually know the location of a particular device with that address, because we have mapped it. So, for example, in the previous case, we saw that if a particular IP address is mapped to this LAN socket in library, whenever we see a device with that particular IP address, we will be pretty much sure it is in library. But IP addresses are not always fixed to locations. Maybe we can clearly say they are not fixed to precise locations like a library socket. So, in an institute, they may actually use an addressing scheme which assigns every connecting device an address from a particular pool. So, now we are just going to concentrate on a pool of addresses. We are not going to fix particular addresses to particular sockets. We are just going to give the devices an address from a given pool. So, we are not going to do some kind of hard fixing of addresses. Now, this addressing scheme is called dynamic addressing scheme. And what we just saw before for the library computer was static addressing scheme. Now, in general, a range of IP addresses can still be mapped to a particular area. Again, we are not going to talk about how exactly these rules can be enforced. Just assume that there are hardware software solutions which can assign certain range of IP addresses to devices connecting from a certain say building or something. So, there are solutions available for doing that. We are not going to go in technical details of it. But so, what we are going to say is, for example, devices that connect to a network from the academic block will get an IP address in this particular range 172.27.18.1 to 172.27.18.200. Now, assume that we get a particular device with the IP address say 172.27.18.15. Now, we are pretty much sure that this device is from the academic block because its IP address is in this particular range. We really do not know where in academic block the device is. But yeah, because we enforced the rule that all devices in this particular building called academic block will get address from this range, we can still say that any device having an address within this range is going to be from academic block where we do not know but from academic block. So, in such a scenario, a device with a particular IP address can still be located. I would say not precisely located but it can still be located. So, within a particular block, a particular building, so what we have actually done is, this done this mapping at a much more higher level. Instead of doing it for a particular socket, we are not doing it for building. So, blocks. Now, this may not just be restricted to a level of an institute. It can actually, these kind of mappings can be done for localities, cities, states, countries. It can actually be done even at the continent level. So, I will give you an example. If you see any IP address on internet in this particular range, you know 103.24.48.02, 103.24.48.25, then it has to be a device connecting from Kanpur. So, because this IP range has been assigned to Kanpur. Similarly, the range 103.255.733, 73.02103.255.755.255 is allocated to Lucknow. So, any device on internet with an IP address in this range is connecting from Lucknow surely. So, basically there is a global database of such mappings and these are available at different levels. They are available at locality, cities, state levels, country level. So, if you have that particular database with you, with the help of that database, if you are given a particular IP address on internet, you can actually tell the location of that particular device, you know, that particular entity. So, there are many websites which can actually tell you the location of a particular IP address. I have given one here, www.iplocation.net. There are actually many others like these. So, one of the homeworks in this particular lecture is to figure out your IP address and see where your location is. The last part of this lecture is about local address. So, we just saw in the case of the library computer that the library computer was assigned an address like 172.27.18.33. Now, the problem is that even though all the things that we studied right now, they are equally applicable say on a local network within an institute or say on the internet, but the addresses which can actually be assigned to a device on intranet. Intranets are actually the internal networks. We call them intranets, just like internet is the network we connect to. Internets are the networks which are internal to a particular organization. So, there are certain IP address ranges that are fixed for the use within an organization and they are not used on internet. So, these are called local addresses. So, one example of such is any particular IP address that starts with 10. So, 10.anything.anything.anything.they are addresses which are only used within an intranet. You will never find a device on internet which will have this kind of an address which starts with 10. So, this is actually an example of local address. So, there are some ranges allocated in the IP address domain which are only applicable to say intranets. Now, a network administrator can actually make use of these ranges and it can actually apply some kind of local mappings. We talked about mappings in which a particular set of IP addresses are reserved for say academic block. These are actually achieved using something called subnets. Subnets are basically subnetworks. So, a network administrator can actually use these IP addresses and then he can divide it in partitions or something and one particular partition can go to say academic block, one particular partition can go to say hostels, another one can go to say lecture halls and all that stuff. So, basically subnets are something which are used very commonly by network administrator to actually partition the IP address ranges. Now, these are actually used on internet as well, but for now we are just going to concentrate on their mappings that we saw in the case of an institute. But this can pretty much be done on internet as well. You can actually assign subnets and basically this is how all the stuff works. The mappings we saw on the basis of continents and cities and states, they are all done using subnets. So, a particular subnetwork is going to be assigned to a particular geolocation. We will just have a quick recap of what we did in this particular lecture. The location of entities interacting with a system can be determined using techniques such as GPS and multilateration. So, GPS was a technique which makes use of satellites and multilateration is something that is done by the mobile service provider. Another way by which entities can actually be identified first on the system is their IP address. This is the identity of a particular entity and then these IP addresses can then be mapped to a particular location using a universal database. So, this database is something which stores some kind of mappings. So, with the help of this database, you can actually pinpoint and tell me where a particular device is. And the last thing we saw was is that an organization can use certain set of IP addresses to define local addresses and these were the local address ranges. So, homework. So, we talked about local addresses and we saw that any IP address that starts with 10 is actually a local address. Well, there are some more local address ranges. So, what you can do is probably just find them out. So, there are basically there are three local address ranges. One I already told you there are two others just find them out. The other thing is try to find out your own IP address. So, there are some commands in operating systems which can actually do that for you. For example, in Windows, it is a command called IP config. If you are using Linux or Mac, you can use IF config. Just use these commands and find out what your IP address is. Then you can go to any particular website which can map the IP address to location. One example is iplocation.net. So, go there and try to figure out what your particular IP address is and what location it is getting mapped to. IPlocation.net by the way can do that for you. On its home page it will show you your IP address as well as your location. Now, what you have to do is match whether the IP address that you are seeing on this particular website matches the one that you saw in IP config whether they are same or not. If they are not same for some people it would not be same by the way. You need to figure out the address that you saw with IP config. Is there anything special about that address? There would be something special by the way. So, just figure out what it is and you will be able to figure out something more about location management with the help of this. That address may not be something that is used on internet. So, just try to figure out what that is. So, this is the end of the lecture on location management. Thank you.