 Scenarios and Rules The general rule is that if the requested PDN Type matches one of the subscribed (provisioned) PDN Types in the HLR/HSS subscription profile, then the created PDN Connection will have that. The requested and subscribed PDN Type is first verified in an SGSN/MME during the connection setup phase after the subscription profile has been downloaded from the HLR/HSS to the SGSN/MME. The second time, the requested PDN Type gets verified against the configured PDN Types in a PGW. If the requested type differs from the subscribed or the configured one, then the type gets changed according to well established rules. The basic matching and conversion rules are listed in Table 4.9. If the subscription profile has multiple PDN Types provisioned for the same APN, then the selection of the selected PDN Type is up to the implementation. For example, the subscription profile may have both PDN Types IPv4 and IPv6 for the same APN. If the PDN Type IPv4v6 is requested it is up to the SGSN/MME implementation to determine which one gets selected. Certain combinations do not make sense, such as having PDN Type IPv4 and PDN Type IPv4v6 for the same APN, since the provisioning overlaps and thus is redundant (unless there are known issues with earlier 3GPP releases in the network, as discussed earlier). Table 4.9 summarizes all the PDN Type selection and fallback rules described SO far. In the table UE Req. stands for the PDN Type originally requested by the UE and NW Table 4.9 PDP/PDN Type matching and conversion rules non-exhaustive summary UE Req. Subscribed DAF NW Req. PGW Result Remarks IPv4, IPv4v6, IPv4_or_IPv6 IPv4, IPv4v6 IPv6, IPv4v6, IPv4_or_IPv6 IPv6, IPv4v6 IPv4v6 IPv4, IPv4v6 IPv4v6 IPv6, IPv4v6 IPv4v6 IPv4, IPv6, IPv4v6 IPv4 IPv4v6 Reject Note 1 IPv4v6 IPv4, IPv4v6 IPv4v6 IPv6, IPv4v6 IPv4v6 IPv4, IPv4v6 IPv4, IPv4v6 Note 1 IPv4v6 Reject Note 1 IPv4v6 IPv4, IPv6, IPv4_or_IPv6 IPv4, IPv6, IPv4v6 IPv4 Note 2 IPv4v6 IPv4, IPv6, IPv4_or_IPv6 IPv4, IPv6, IPv4v6 IPv6 Note 3 IPv4v6 IPv4v6 IPv4v6 Note 2 IPv4v6 