turn. Both the outgoing INVITE messages are associated to the incom- ing INVITE message in a back-to-back relation. The Indirection Service would reply with SIP OK carrying the access information related to the requested chan- nel, for example, server address, codec, and SO on. The Network Service then inter- acts with the Optical Network Control and Management Plane using proprietary signaling to set up the network as required. If both INVITE messages are success- ful, as indicated by the receipt of SIP OK messages from Indirection and Network Services respectively, SIP OK will then be sent to the requester along with the video information (copied from the Indirection Service's SIP OK), based on which the requester can start streaming video. 9.3.2 Multimedia Services over EPON Access Network EPON, specified by IEEE 802.3ah, enables multiple ONUs to share a symmetri- cal 1 Gbps downstream and 1 Gbps upstream bandwidth resources. As a low- network-cost and high-data-rate network, EPON is an attractive solution to broadband access networks for business and residential users. In order for Design and Implementation of an IMS-Based Testbed IMS core (CSCF, HSS) IMS client Application servers 18.Ok 15. Ok (server IP) 1. REG 6. INVITE Composite INVITE service 7. INVITE 13. Ok Indirection 9. INVITE service Network service 8. INVITE 12. Ok 14. Ok (server IP) IP network 2. REG Security service 4. INVITE 5. INVITE 16. Ok (server IP) Mobile service 17.Ok discovery 11. Done 10. Connect Control plane Fixed IMS/Video Splitter Managed optical client network Video server 1 Video server 2 Figure 9.5 Signaling sequence for mobile phone initiated service. multimedia service to be efficiently supported on the EPON network for sub- scribed users, the EPON should be able to allocate and guarantee the downlink bandwidth resource for these multimedia services, that is, resource on EPON is allocated according to user's service requirements. Furthermore, to allow users to access subscribed multimedia services, such issues as user authentica