0108 Generating the Response

 

   When a UAS wishes to construct a response to a request, it follows

   the general procedures detailed in the following subsections.

   Additional behaviors specific to the response code in question, which

   are not detailed in this section, may also be required.

 

   Once all procedures associated with the creation of a response have

   been completed, the UAS hands the response back to the server

   transaction from which it received the request.

 

8.2.6.1 Sending a Provisional Response

   One largely non-method-specific guideline for the generation of

   responses is that UASs SHOULD NOT issue a provisional response for a

   non-INVITE request.  Rather, UASs SHOULD generate a final response to

   a non-INVITE request as soon as possible. When a 100 (Trying) response is generated, any Timestamp header field

   present in the request MUST be copied into this 100 (Trying)

   response.  If there is a delay in generating the response, the UAS

   SHOULD add a delay value into the Timestamp value in the response.

   This value MUST contain the difference between the time of sending of

   the response and receipt of the request, measured in seconds.