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Chained S2a/S2b and S8 used when VPLMN has business relationship with Non-3GPP Networks and S-GW in VPLMN includes local non-3GPP Anchor.
The following are some additional considerations in this case:
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Gxc is used only in the case of PMIP-based S8 and for 3GPP access.
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Gxc is not required for Trusted Non-3GPP IP Access; Gxa is used instead to signal the QoS policy and event reporting.