[SIPForum-discussion] REGISTER: Request or response?

[Michel Bensoussan]

Hello

Looking on RFC 3261, paragraph 20. Header Fields, Table 3, we can see 
that the Warning header may only appear in responses (r), and that it is 
optional (o) in the REGISTER (REG) method.

It this a contradiction?
REGISTER isn't by definition a Request and not a response?

Can we use Warning header in a REGISTER message?

If I cannot use Warning, is there a way to transmit a proprietary 
parameter in the REGISTER message?

Thanks.

Regards,
Michel.