When operator would like to configure S12 interface in place of S4 interface ?

Question

I am looking for scenarios in which MME/SGSN purges an UE. And also what these nodes do as part of this procedure.

Answer 1

Never

Yes, this is the answer. Never. Why? Because read anything about those two and you will notice what is on the top of UDP in both cases.

Do your homework guys.

Comments

Ah!
When you will finally know what is running on top of UDP in both cases please do not stop yourself from GOOGLING to find what for those on-top-of-UDP-protocold are used for.

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If an operator has PDN connectivity only and a UE (UMTS-user) want to access data. It now depends upon the Operator configurations that how he is carrying the user up to Packet data network.
Because it has two implementation ways: either it can configure through S4 interface or S12 interface. That is what I have asked on which circumstances an Operator would prefer to implement which interface he may use.

For your information both interfaces have GTP-U protocol on top of UDP. I suggest you to don’t Google too much so that you forget the stack itself.  First you should do your homework and then re-commend someone else. It will remind you some etiquette.
Read something before you comment. If you didn’t understand my question, you could cross comment to me for asking the real problem. It would be nicer instead of suggestions.

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Hello,the s12 and s4 interface can and should co-exist. The s12 interface allows a Direct Tunnel between the RNC and S-GW, While the S4 when used as an User Plane interface acts as a Two Tunnel PDP Context, that is: One Tunnel between RNC and SGSN (using Iu-PS interface) and another tunnel (using s4 interface) between SGSN and S-GW.

The S12 is a user plane only interface, while the s4 interface is a control and user plane interface.

Hope that helps, even after more than a year.

BR,