what is the functionality or role of ePDG in lte network ?

Question

For me, the role of SGW is packet forwarding w.r.t user plane ? Is it possible MME interacts with PGW directly ?

Answer 1

ePDG stands for "Evolved Packet Data Gateway". It sits between PGW and untrusted (unlicensed ) non-3GPP access network and provide LTE services through untrusted non-3GPP network. ePDG is responsible to make IP sec tunnel between UE(which is located in untrusted non-3GPP network) and PGW. it is responsible for security and tunnel authentication and authorization. ePDG also acts as local mobility anchor.

Comments

May I know what is untrusted non-3GPP Network?

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Say for example one area/geography is reliance network and other is airtel then these two network are called untrusted network. The fact is these two are separate business entity so are not trustworthy of each other and more importantly they would not have connectivity using private network so need to connect using public or third party IP network so there is a requirement of secure channel between these two if needs to communicate/interwork.
I hope this clarifies the doubt.