[Sip-implementors] Is The ID Parameter Extraneous

[Ngo, Dai (c)]

Hi,   In the draft-ietf-sip-events-05.txt section 4.1.4.1 and 4.1.4.2 it mentions an optional ID parameter, which can be used to establish a new "dialog" in the EVENT header. Is this parameter extraneous when we already have the From (+From-tag), To (+To-Tag), Branch, Cseq, etc. or am I missing something?   Thanks for explaining and regards,   Dai Ngo