LTE: What does mean by "mix of S5/S8 connectivity and Gn/Gp connectivity is not supported for an UE simultaneously" ?

Question

while going through 3GPP 23.401, I stopped at PGW functionality. The following statement was written.
"If a UE is accessing multiple PDNs, there may be more than one PDN GW for that UE, however a mix of S5/S8 connectivity and Gn/Gp connectivity is not supported for that UE simultaneously". I couldn't understand it. Can someone please elaborate it.

Answer 1

S5 is local breakout. S8 is home-routed. Basically I think it means that a UE's subscription is such that it can connect to either, all of its "home" PDNs , or "visited" PDNs. The HSS manages the subscription. Now if the UE has to be supported a mix of "home" and "visited" PDNs, it has to be managed by both "home" and "visited" HSS, which is not a practical scenario. My thoughts, of course!