From the course: Telecom Network Evolution: 2G-to-6G Technologies, Architecture, and Key Concepts

User identity: GUTI

From the course: Telecom Network Evolution: 2G-to-6G Technologies, Architecture, and Key Concepts

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User identity: GUTI

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(upbeat music) - [Instructor] We talked about the international mobile subscriber identity, which is IMSI, which helps to have a communication within the device and the network. Now, IMSI is a permanent ID and it cannot be used every time for the communication because it poses privacy and security risk. In that case, we have a new term, which is GUTI, which is globally unique temporary identity. Now, this is used to protect the user's permanent identity, which is IMSI. We talked about the IMSI in detail, that TMSI is used to encapsulate the IMSI, but for the initial attach and authentication purpose only. What about the continuous communication after that? So GUTI comes into picture in that case. It enhances the user privacy and supports efficient paging. Now there are different components of GUTI. It is heavily focused on the MME group IDs and MME code. We have the different MMEs where we have different groups and specific MME would be then representing a particular user. We also have the TMSI, which we know is unique for individual users, but not globally. Then we have the PLMN ID, which is MCC and MNC. When the PLMN ID combined with the MME identifier, it becomes a globally unique MME identifier. It uniquely identifies the MME. Then when combined the MME with the TMSI, it gives us a GUTI, which is globally unique temporary UE ID. It does not reveal the permanent identity of the UE and it is globally unique. Now, if you look into the example of GUTI, for example, there is a particular user in a particular country, which is USA, it has a particular operator with the code of 260. The network code is 260 here. We have MME group ID, which is identifying the group of MME, serving this particular network. And then we have a specific MME, which is serving this user with a code of 12. Then we have the TMSI for individual user because we are not revealing the IMSI ID, and hence the complete GUTI might look like this alpha numeric long digits, which we can see here. Now, this is the GUTI value, which is globally unique, even across different countries and operators, and that's what we want. We want it to be unique so that we can map it with the IMSI, the global temporary ID to be mapped to the global permanent ID so that the identity would not be revealed from security and privacy perspective. Now, if we look into the comparison, so IMSI is the subscriber unique identity, whereas the GUTI is the temporary ID, but it is globally unique also. Now the IMSI is permanent ID, GUTI is not permanent. The IMSI is used for initial authentication, whereas GUTI is used after attached process. Now, GUTI is also used in 5G, it is not only in 4G, but instead of IMSI and TMSI, we have different terms which we'll touch base upon shortly. So in 5G networks, there are several critical identifiers to manage user sessions securely. GUTI is one of that. Similar to what we have seen in 4G, we have the MME, here we have the AMF, the access and mobility function, which does the authentication and registration part. So we have the similar kind of concept where we have the different region. Within the region, we have different sets of AMF, and within that set, we have a particular AMF serving a particular user, which we are talking about here. And we have a globally unique AMF ID. When combined with the TMSI, it gives us the GUTI, 5G GUTI in this case. Now 5G GUTI is doing the similar thing, but it has certain new terminologies added here. It has a SUPI, it has a SUCI, and it has NAI, which we are going to talk about in the subsequent light.

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