The DVB server-based FCC solution has many commonalities with DVB LMB RET unicast repair because both solutions leverage the same protocol/architecture concepts. The main aspects of these common protocol/architecture concepts are specified in: RFC 4585 [84]: Extended RTP Profile for Real-time Transport Control Protocol (RTCP)-Based Feedback (RTP/AVPF). RFC 4588 [85]: RTP Retransmission Payload Format. RFC 5760 [111]: RTCP Extensions for Single-Source Multicast Sessions with Unicast Feedback. The DVB server-based FCC solution leverages IETF RFC 6285 [116], also referred to as RAMS (Unicast-Based Rapid Acquisition of Multicast RTP Sessions). RAMS specifies the interactions between an RTP receiver and a "Retransmission Server", and defines new RAMS RTCP FeedBack messages (RAMS-R, -I and -T) for controlling the burst process. This RAMS "Retransmission server" is responsible for sending the RTP burst (resulting in the FCC experience) but also for sending retransmissions in response to retransmission requests. RFC 6285 [116] stipulates that RTP retransmissions and RTP burst packets are transmitted in one and the same unicast RTP (retransmission) session, with the RTP burst packets formatted with a retransmission payload header (RFC 4588 [85]). DVB server-based FCC will not deviate from these rules, which means that when both the RET and FCC services are offered for a DVB LMB service, and a HNED makes use of both these services: The DVB LMB RET server and DVB FCC server coincide and are one and the same. This server will be referred to in this text as the DVB FCC (/LMB RET) server.
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