All right. So, let's talk about some of the core network elements in the effort that's going on to virtualize these and that decomposition that we spoke of in the past. The targets really come into play when we look at the transformation that's taking place as a motivator behind the 5G introduction. So, while we've got the engine open, if you will, we can do some interesting things in the core of the network and those elements that we really want to look at and talk about that are in the process of being virtualized or that had been virtualized start with the evolved packet core and then we dig into that. So, when we look in a long-term evolution the thing that's also called as 4G, we see that once we egress from the enhanced NodeB, the eNB part of the radio access network or through the EU trend we come into the network and are inter-operating with the elements that we call the evolved packet core, the EPC, for simplification. This provides us with that IP consolidation that was a prime mover actually for LT for the 4G. So, in addition to the bandwidth increases that we got when we introduced the 4G and the LTE, one of the things that we also did was we allowed for the collapsing of two networks that existed inside the core of the network and that is the data network and the voice network. Again, we sometimes forget about the fact that we still use these devices to make phone calls. The voice portion of the network prior to LTE was a separate set of capabilities that handled that TDM, that voice access and actually over different channels but with LTE we were able to introduce voice over LTE, VOLTE as it's called. But in order to support that, some of those calls still needed to egress the network and interface with legacy devices. So, if you were calling an enterprise for example, you may need to LT egress it's not going to remain wireless or you may actually go over someone else's network, that is the two devices are on two different mobile network operators or one of them could terminate into a classical landline. But in order to support that capability we had to have another technology that was called IMS. Now IMS goes back a long ways it started being standardized probably in the late 1990s early 2000s and it stood for IP multimedia services. A tremendous amount of capability but for the most part why IMS is used for today in the core of the network is to support voice services and that is to provide the the interoperability that needs to take place so that if we're calling an orphanage in Honduras, for example, that still has still has a patch phone, if I'm calling them from from a mobile phone we can still have a conversation about an upcoming trip or whatever happens to be the example would be. So, again we've talked about the globality of the communication service provider network and in that reach of that connectivity and IMS is a critical portion of that and IMS also is one of those elements that while we may look at it as legacy element, it has been virtualized and we're going to touch very briefly on some of the configuration elements inside that. So, let's dig down and look at those elements inside the IMS, this is a very high level abstracted diagram. Sometimes you want to think of it as a tool of an abstracted diagram of the IMS solution itself because again if you look at a communication service provider network the IMS is going to be distributed across there geography. For your very large geography you may have one of these for every 10 million or 20 million subscribers over your network and and you're going to put some locality in it because as I said the IMS actually provides that interworking function. If you look at what we've got here the media layer itself this alphabet soup that's down here of a MGW or media gateway platform, if you will, that actually provides physical interfaces to a legacy PSTN interface. So if you've got one or two interfaces from the legacy telco days that are still required to deliver access as the egress to your network into some other network and that's the medium that used, this media gateway, performs the digital transformation that takes place so that those voice protocols inter-operate. Because a Voice Protocol on a mobile device is actually different than the voice protocol on an E1 or 21 interface. I'm not just talking about the signaling aspects which are also different but the actual popularization of the voice itself is different, and we've got me resource control functions that are associated with that in their. Move our our concentration up into the control layer and IMS was originally designed with his segregation in place and there are a lot of control functionalities so this is signalling aspect. This is setting up and tearing down sessions. This is associated with the billing aspect, running timers and if you've got a prepaid type of a device in there ensuring that the call is managed according to those rules where prepay or postpay so that's crediting the account correctly. Then also there are very large databases the HSS is it just as a very large subscriber database that these network elements used to determine whether or not this device has international calling access for example, would be one of the things that the HSS would be involved in. The PCRF again that's a billing aspect that's associated with it. All of these devices that we see at the control layer were segregated out from the specification early on and function as signaling plane type of devices and in the beginning of our network functions virtualization efforts, the vendors that we're providing these solutions found that it was actually very easy to virtualize these elements because in essence they were already running on standard high-volume servers. There was lot of system integration work that took place there but to take them and put them on virtualized servers by driving hypervisors underneath them was not the heavy lift that we see that we find that the re-architecting some of the other elements in the network. In the top again, application servers. So, we talked about voice services I gave you a couple of examples, simple voice services. But the IMS solution is also capable of providing services to enterprise IPPPX type functionality where you can enterprise and you've got desk phones that are still being used by those enterprises, you can actually support that type of functionality of an IPPPX off of off of an IMS system. So, not only does it apply to the VOLTE type of use case or voice over Wi-Fi type of use case but depending on the capabilities of the application servers. Again, these are just signaling type control plane devices around handling enter the media are great candidates and have been virtualized for some time in the network. So we're not going to spend a lot more time digging down into the IMS itself. Some of the protocols are listed here signaling Initiation Protocol such as solely on the control plane aspect of things. Diameter protocol is a query response protocol. So what I'm going to think about as being accessing databases or diameter and the SIP is setting up and tearing down those sessions and then the other protocol that Megaco is actually an indication of one that would actually be carrying the traffic. Then you see that the EPC, the evolved packet for core, the Packet Gateway of it interfaces into both the control function the CSCF for the IMS as well as into the policy control function for that element.
