I am doing a Java RFC 3550 (RTP) implementation , and I ran into a little problem:
In chapter 11 , paragraph 2, states that:
(...) A participant MUST NOT assume that the source port of an incoming RTP or RTCP packet may be used as a destination port for outgoing RTP or RTCP packets. When RTP data packets are sent in both directions, each participant in the RTCP SR packets MUST be sent to the port that the other participant indicated to receive RTCP. (...)
RTP has no mechanism for reporting these addresses and ports (prior to SDP or some other installation protocol), which would lead me to understand this paragraph as "if you get data from an unknown source, just drop it."
But section 6.3.3 basically says that when an RTP or non-BYE RTCP packet is received with an unknown SSRC, a new member must be added to the table.
So to summarize:
- You must add a new member when an unknown SSRC is received;
- You cannot use the IP / port of the packet source as the packet destination for this member;
- SDP does not determine the SSRC that will be used by each of the RTP participants;
- You can manually add RTP members (discovered in other ways), but you do not know what SSRC is.
, : SSRC?