As we know, if one side's UA want change it's receiving address, it needs a new O/A procedure. Not considering symmetrical RTP, can UA change it's sending address during session?
IETF level:
By current RFC3264, it seems that there's no normative text to forbid such behavior.
3GPP(definition of media flow):
IP Flow: Unidirectional flow of IP packets with the following properties:
- same source IP address and port number;
- same destination IP address and port number;
- same transport protocol (port numbers are only applicable if used by the transport protocol).
Media Flow: One or more IP flows carrying a single media instance, e.g., an audio stream or a video stream. In the context of this specification the term Media Flow is used instead of IP Flow regardless of whether the actual IP packet corresponds to media plane information (e.g. audio RTP flow) or control signalling (e.g. RTCP or SIP Signalling).
[Inference] By 3GPP's definition, 3GPP's usage seems UE can not change it's sending address(the media flow should has same source IP address and port number).
And informative: I heard lots of NAT/SBC equipment developers/providers said that the media might be blocked by their equipment if UE changing sending address during session.
Today, someone asked me the problem again. But I am not sure about the answer, so I'd like to hear people's points here.
Thanks,
Gao
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