Section: 16a.1 Diameter Authentication and Authorization
Content: Diameter Authentication and Authorization shall be used according to RFC 7155 [120]. The GGSN/P-GW and the Diameter server shall advertise the support of the Diameter NASREQ Application by including the value of the appropriate application identifier in the Capability-Exchange-Request and Capability-Exchange-Answer commands as specified in IETF RFC 6733 [111]. The Diameter client function may reside in a GGSN/P-GW. When the GGSN/P-GW receives an initial attach (e.g. Create PDP Context) request message the Diameter client function may send the authentication information to an authentication server, which is identified during the APN provisioning. The authentication server checks that the user can be accepted. The response (when positive) may contain network information, such as an IPv4 address and/or IPv6 prefix for the user when the GGSN/P-GW is interworking with the AAA server. The information delivered during the Diameter authentication can be used to automatically correlate the users identity (the MSISDN or IMSI) to the IPv4 address and/or IPv6 prefix, if applicable, assigned/confirmed by the GGSN/P-GW or the authentication server respectively. The same procedure applies, in case of sending the authentication to a ‘proxy’ authentication server. Diameter Authentication is applicable to the initial access (e.g. primary PDP context or the default bearer). When the GGSN/P-GW receives a positive response from the authentication server it shall complete the initial access (e.g. PDP context activation) procedure. If a failure or no response is received, the GGSN/P-GW shall reject the initial access (e.g. PDP Context Activation) attempt with a suitable cause code, e.g. User Authentication failed. The GGSN may also use the Diameter re-authorization procedure for the purpose of IPv4 address allocation to the UE for PDP type of IPv4v6 after establishment of a PDN connection. For EPS, the P-GW may also use the Diameter re-authorization procedure for the purpose of IPv4 address allocation to the UE for PDN type of IPv4v6 after establishment of a PDN connection. The use cases that may lead this procedure are: - Deferred IPv4 address allocation via DHCPv4 procedure after successful attach on 3GPP accesses. - Deferred IPv4 address allocation after successful attach in trusted non-3GPP IP access on S2a. - Deferred IPv4 home address allocation via DSMIPv6 Re-Registration procedure via S2c.