Subject: [Sip] Question on Histrory-Info: the basic rules for adding the index

From: Takuya Sawada <[email-masked]>
Date: Mon, 24 May 2004 18:51:12 +0900

Hi,

In the summarized basic rules for adding the index in section
4.3.3.1 of History-Info draft, item 2 says;

>     2. If the Request-URI indicates a resource that this proxy is not 
>     responsible for, then the lowest/last digit of the index is 
>     incremented (i.e. a new level is not created).  For example, if the 
>     index in the History-Info header of the received request was 1.2, 
>     then the index in the History-Info header field added by this proxy 
>     would be 1.3.

In RFC 3261, section 16.5, on determining request targets at SIP proxy;

>    If the domain of the Request-URI indicates a domain this element is
>    not responsible for, the Request-URI MUST be placed into the target
>    set as the only target, 
<snip>
>       A proxy can only change the Request-URI of a request during
>       forwarding if it is responsible for that URI.  If the proxy is not
>       responsible for that URI, it will not recurse on 3xx or 416
>       responses as described below.

Note that Request-URI in the above sentense is after preprocessing at
the proxy. 
I think that If the Request-URI indicates a resource that the proxy is not
responsible for, the Request-URI will not change. Retargeting on receiving
3xx will not ocuur, neither.
Why do you need to record the history of Request-URI at the proxy
which is not responsible for the Request-URI?

I think the basic rules item 1 is enough and simpler solution.

Then, for example, the sequence in section 4.5 can be seen as
the following;

   UA1        Proxy1  Proxy2     UA2      UA3      UA4      UA5 
                
   |            |         |        |        |        |        | 
   |--INVITE -->|         |        |        |        |        | 
   |            |-INVITE->|        |        |        |        | 
                 Supported: Histinfo 
                 History-Info: <sip:Bob@P1>;index=1, 
                               <sip:Bob@P2>; index=1.1 
   |            |         |        |        |        |        | 
   |            |         |-INVITE>|        |        |        | 
                  History-Info: <sip:Bob@P1>;index=1,  
                                <sip:Bob@P2>; index=1.1, 
                                <sip:User2@UA2>; index=1.1.1 
   |            |         |        |        |        |        | 
   |            |         |-----INVITE ---->|        |        | 
                  History-Info: <sip:Bob@P1>;index=1,  
                                <sip:Bob@P2 >; index=1.1, 
                                <sip:User3@UA3>; index=1.1.2 
   |            |         |        |        |        |        | 
   |            |         |-------INVITE------------>|        |  
                  History-Info: <sip:Bob@P1>;index=1,  
                                <sip:Bob@P2 >; index=1.1, 
                                <sip:User4@UA4 >; index=1.1.3 

   /* All Responses from the INVITEs indicate non-success/non-
   availability*/   
  |            |         |        |        |        |        | 
  |            |<-480 ---|        |        |        |        | 
               History-Info: <sip:Bob@P1>;index=1,  
                  <sip:Bob@P2>; index=1.1,   
                  <sip:User2@UA2?Reason:SIP;\ 
                   cause=408;text="RequestTimeout">;index=1.1.1,                  
                  <sip:User3@UA3?Reason:SIP; \        
                   cause=487;text="Request Terminated">; index=1.1.2, 
                  <sip:User4@UA4?Reason:SIP;\         
                   cause=603;text="Decline">; index=1.1.3 
  |            |         |        |        |        |        | 
 /* Upon receipt of the response, P1 determines another route for the 
  INVITE, but finds that it matches some routes already attempted  
 (e.g. UA2 and UA3, thus the INVITE is only forwarded to UA5, where  
  the session is successfully established  */ 
  |            |         |        |        |        |        | 
  |            |----------------INVITE --------------------->| 
                History-Info: <sip:Bob@P1>;index=1, 
                   <sip:Bob@P2>; index=1.1,  
                   <sip:User2@UA2?Reason:SIP;cause=408;\ 
                    text="RequestTimeout">;index=1.1.1,                      
                   <sip:User3@UA3?Reason:SIP;cause=487;\ 
                    text="Request Terminated">; index=1.1.2, 
                   <sip:User4@UA4?Reason:SIP;cause=603;\ 
                    text="Decline">; index=1.1.3 
                  <sip:User5@UA5>;index=1.2  
  |            |         |        |        |        |        | 
  |            |<-----200 OK---------------------------------| 
  |<--200 OK---|         |        |        |        |        | 
  |            |         |        |        |        |        |  
  |--ACK --------------------------------------------------->| 

Regards,
Takuya

--------
Takuya Sawada
KDDI Corporation (KDDI)
Garden Air Tower, 3-10-10, Iidabashi, 
Chiyoda-ku, Tokyo 102-8460, Japan
Tel: +81-3-6678-2997
Fax: +81-3-6678-0286
[email-masked]

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