Yes, but it can be skipped - for instance if you're autoanswering you could skip the 100 and jump straight to the 200. Or similarly if you're generating ringback jump straight to the 183. There's no reason that 100 is needed first.

-Steve


On 21 April 2011 15:31, Kristian Kielhofner <kris@kriskinc.com> wrote:
When using UDP it's typically a good idea to fire some kind of
provisional response ASAP to prevent the SIP retransmission timers
from freaking out and repeatedly resending the initial INVITE.  That's
where 100 Trying comes in.

On Thu, Apr 21, 2011 at 10:13 AM, Brian West <brian@freeswitch.org> wrote:
> That seems like  rather weird request since the 100 trying isn't required.
>
> /b

--
Kristian Kielhofner

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