Section: 13.2.2 Other configuration by the Intranet or ISP (IPv6 only)
Content: When using IPv6, in some situations the MS may need additional configuration information from the Intranet or ISP besides the IP address. It may for example be IMS related configuration options (see 3GPP TS 24.229[ IP multimedia call control protocol based on Session Initiation Protocol (SIP) and Session Description Protocol (SDP); Stage 3 ]  [47]). If the MS is DHCP capable and the IPv6 address has been allocated using Stateless Address Autoconfiguration, the MS may use a procedure as in the example below to configure additional external network protocol parameters, or other parameters that apply to the Intranet or ISP. The GGSN shall in this case indicate to the MS that there is additional configuration information to retrieve by setting the O-flag in the Router Advertisements. This shall be configured per APN in the GGSN. The following description bullet items describe an example of a signal flow, where the MS directs an Information-Request to the All_DHCP_Relay_Agents_and_Servers multicast address. The MS may also direct the message to a specific server instead of all servers. For a detailed description of the DHCPv6 messages refer to the DHCPv6 IETF RFC 3315 [46]. The sequence is depicted in figure 16f. 1) A Router Advertisement with the O-flag set, is sent from GGSN to TE to indicate to it to retrieve other configuration information. 2) The TE sends an INFORMATION-REQUEST message with the IP destination address set to the All_DHCP_Relay_Agents_and_Servers multicast address defined in the DHCPv6 IETF RFC 3315 [46]. The source address shall be the link-local address of the MS. The DHCP relay agent in the GGSN shall forward the message. 3) DHCP servers receiving the forwarded INFORMATION-REQUEST message, reply by sending a RELAY-REPLY message, with the "Relay Message" option including a REPLY message with the requested configuration parameters. The TE chooses one of the possibly several REPLY messages and extracts the configuration information. EXAMPLE: In the following example a request for information with use of DHCPv6 from end to end is shown. Figure 16f: DHCPv6 Other configuration signal flow