<p>If I am not mistaken, Reg-ID 0 is invalid. RFC 5626 says</p>

<p>c-p-reg        = "reg-id" EQUAL 1*DIGIT ; 1 to (2^31 - 1)</p>

<p>I think a 439 message, like a reg-id doesn't exist is appropriate. Sending 200 Ok is definitely wrong.</p>

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