 The concept of evolution culminates with the emergence of the entity in the core Which is known as the evolved packet core So we know that the core network in classical GSM network actually meant The base station controller the MSc, HLR, VLR, OSS, etc. But in today's networks LTE, LTEA, we don't see many of those terminologies because now we have the evolved packet core That contains multiple gateways, which are sharing the functionality for the user as well as for the signaling planes So we'll see how this evolved into EPC. We look at the context of it And then we are going to look at the most important gateway nodes and the controlling nodes So basically evolved packet core is the main part of the overall evolution which took place If you remember we talked about having higher bit rates, better modulation techniques, etc. On the air interface side, that is the radio network control part and the Radio link control part, but here we are talking about the core side which forms the Essence of the overall connectivity for the data networks today. So the word Evolution is not by Fun or it is not by accident. There is a history to it and it says That whatever network elements we saw starting from the SGSN and GGSN to the other advanced functionality We see that essentially GPRS was the first step in providing data connectivity. So the evolution started from there So that is why even in today's evolved packet core architecture, we would see these Network elements to be there some as They are and others probably renamed so the components starting from the gateway elements are the Mobility management entity that takes care of the handovers The gateways which provide the bearer parts Starting from the serving gateway to the packet gateway that provides connectivity to the Extraneous networks that is the IP network or the internet Per se and then we have certain controlling nodes which perform the functionality of somewhat the service stratum which is working together with the Transports stratum. So we have the home subscriber server which is akin to the home location register and we have the policy and charging rules function PCRF which is similar to what we had the AAA services in classical networks If you look at the evolved packet core, we can say that Starting from the Lower side of this diagram. We see we have the user equipment then we have the Radio connectivity that is the Terrestrial radio connectivity Here we have the starting from the classical G Iran that is GSM edge radio access network Once we had the data connectivity from the old days We have the entities like the base station and the base station controller in UMTS universal mobile telecommunication standard based radio access network We have the node B and the radio network controller, which only persisted up till release seven Then we have the evolved U-tran that includes now E node B and radio network controller is Obviated now this E node B is now connected to the evolved packet core the block or the Super functional module that you see right above it Here we have some Functionalities that we have just seen the names of including the packet gateway the serving gateway mobility management entity the charging and Rule function policy and charging rule functions home subscribers server SGSN we don't see GGS in here But in one way or the other the serving gateway and the the packet gateway are now serving as the GGSN, which is the gateway gprs support node We also have the evolved packet data gateway, which has a bearer path with the packet gateway So wherever you see this dotted line that actually means it is for control signaling and wherever you see this Continuous line that means it's the user connectivity So we also see the triple a server for Non 3GPP Technologies the earliest telecom architectures, so this is a fairly complicated diagram that includes holistic view in fact a comprehensive view of how the data networks have evolved and how the evolved packet core addresses contemporary technology integration and backward technology integration as well