 We have discussed the NGN functional architecture in terms of the services stratum, the transport stratum and their inner details in quite much depth. However, there are certain additional topics which may not necessarily be related to the architecture as such, but they are important to discuss because the overall NGN vision cannot be realized without them. Specific to the topic of numbering, naming and addressing, we have discussed this in some of the earlier topics. If you remember, when we talked about E.164 and Enum, we did talk about numbering, naming and addressing in NGNs. Now we are going to just cap the topic and discuss issues which we might have missed or which we might have not discussed back then. In this module, we shall start with a quick recap of what are the two different addressing schemes in the traditional telecom world and the IP world and how can we look at the confluence of both of these in the form of NGN. So let's talk about divergence first. We understand that numbering, for instance, numbering mechanisms to label or identify devices, naming them for human consumption and addressing them to deliver traffic to them or get traffic from them is an important activity. Traditional telecom networks as in the PSTNs and PLMNs from the telecommunications service providers perspective all use E.164. Primarily based on all IP uses DNS for naming and addressing and IP address for numbering and addressing. It means that both DNS and IP address do something which E.164 does single-handedly. Now E.164 networks cover both the landline networks and the wireless networks. In landline networks, the destination IP address, the destination addresses are marked by E.164 and the switching at the exchanges are also done through E.164. In the GSM networks and the UMTS networks, we have additional terminologies for instance MSISTN which is a unique identifier of the device which characterizes two things. Number one, it's a digital device end to end that is the local loop is digital and the core side is also digital. Then it is mobile so MSISTN characterizes these two things. Then we have subscriber related information in SIM we call MC international mobile subscriber identity. In 3GPP we have yet another additional information called ISIM. All these combined are pretty much the scope of the telco. When we look at the internet, in internet the identification is done through names. The domain names, the uniform resource identifiers which are based on the protocols which are used and quite different email addresses like Ali, Adlerid, some server like gmail.com. Here in this case, routing is a different activity which is based on IP addresses. So the domain names are responsible for identification and IP addresses for routing. These two are combined together through a mechanism called DNS. Now with these two worlds which are trying to get abridged as in NGNs, some reality has to be accepted that is the dominant numbering scheme because of the availability of the devices themselves is E.164. We have the landline phones and we have the handheld devices like smartphones, tablets, laptops, phablets, etc. So in NGN we have Inam if you recall we discussed it. Now the dominant naming and addressing in internet has always been DNS that works along with IP address. So it means that we need some kind of translation that is all naming schemes regardless of what their origin may be have to map to IP address through DNS that is the take home.