So *relying* on a 100 Trying is dangerous, but keeping an eye out for it is okay. To the OP (Neil) I&#39;d ask: what is the failure condition when a 100 Trying does not come back? Is that a form of &quot;gateway down&quot;? Is it possibly to use SIP OPTIONS to test this instead of relying upon a 100?<div>
<br></div><div>-MC<br><br><div class="gmail_quote">On Thu, Apr 21, 2011 at 8:55 AM, Steven Ayre <span dir="ltr">&lt;<a href="mailto:steveayre@gmail.com">steveayre@gmail.com</a>&gt;</span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
Yes, but it can be skipped - for instance if you&#39;re autoanswering you could skip the 100 and jump straight to the 200. Or similarly if you&#39;re generating ringback jump straight to the 183. There&#39;s no reason that 100 is needed first.<br>


<br>-Steve<div><div></div><div class="h5"><br><br><br><div class="gmail_quote">On 21 April 2011 15:31, Kristian Kielhofner <span dir="ltr">&lt;<a href="mailto:kris@kriskinc.com" target="_blank">kris@kriskinc.com</a>&gt;</span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204, 204, 204);padding-left:1ex">

When using UDP it&#39;s typically a good idea to fire some kind of<br>
provisional response ASAP to prevent the SIP retransmission timers<br>
from freaking out and repeatedly resending the initial INVITE.  That&#39;s<br>
where 100 Trying comes in.<br>
<div><br>
On Thu, Apr 21, 2011 at 10:13 AM, Brian West &lt;<a href="mailto:brian@freeswitch.org" target="_blank">brian@freeswitch.org</a>&gt; wrote:<br>
&gt; That seems like  rather weird request since the 100 trying isn&#39;t required.<br>
&gt;<br>
&gt; /b<br>
<br>
</div>--<br>
<font color="#888888">Kristian Kielhofner<br>
</font><div><div></div><div><br>
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