A new TLV RAMS-I element for RAMS
Huawei Technologies
Huawei Technologies
[I-D.ietf-avt-rapid-acquisition-for-rtp] defines a method for rapid acquisition of multicast sessions (RAMS). Upon accepting the first RAMS-R message, RS MUST echo an RAMS-I message as a response to RR. This document proposes to optionally convey a parameter called unicast backspace in the RAMS-I message. Unicast backspace is the RTP timestamp difference between the first unicast burst packet to be sent and the latest primary multicast packet in the buffer of RS. The RTP timestamps values for these packets are taken from the primary multicast stream. The parameter is a constant once RS chooses a starting point for the unicast burst. This parameter can be used by RR to determine when to join the primary multicast session. RR would not rely on RAMS-I to revise the earliest multicast join time after the burst rate is changed by RS and therefore is immune to the lose of RAMS-I. Moreover, if this parameter is known, RR with appropriate playback control can reduce the additional end-to-end delay introduced by the RAMS process or can enable the RS to serve the RR with shorter burst duration and therefore save the bandwidth of RS export and the burst forwarding path.