Re: [M3UA] ASP UP in IPSP DE mode

Santhana,

Please see comments below...

Santhana wrote:                               (Thu, 06 Jan 2011 10:26:34)
>    Dear Brian
> 
>                In IPSP DE mode, is the double exchange of ASP UP messages
>    mandatory? As per the M3UA RFC 4666, in section 4.3.4.1.2 para2 says
>    double exchange of ASPSM is MUST.
> 
>    Whereas in section 5.6.2 in the sequence diagrams it says second
>    exchange is optional.
> 
> 
>    If it is mandated, then what purpose it solves?
> 
> 
>    Regards
> 
>    Santhanakrishnan

I don't know what purpose it solves.  There was a change from RFC3332 to
RFC4666 in 4.3.4.1.2 para2, but the example in 5.6.2 did not change.  But
then the editor of RFC4666 did a poor job of keeping examples up to date
with the text.

 RFC 4666

   Alternatively, when using the IPSP DE model, an interchange of ASP Up
   messages from each end MUST be performed.  Four messages are needed
   for completion.

 RFC 3332

   Alternatively, an interchange of ASP Up messages from each end can be
   performed. This option follows the ASP state transition diagram. It
   would need four messages for completion.

The only reason I can remember for requiring double exchange of ASP-UP
for DE was so that a misconfiguration between SE and DE would be detected.
The original intent from RFC 3332 is described at the end of example
RFC4666/5.6.2 or RFC3332/5.5.2 (which are identical).

   In this approach, only one single exchange of ASP Up message can be
   considered as enough since the response by the other peer can be
   considered as a notice that it is in ASP_UP state.

But, in general, DE mode is always a situation of performing two message
exchanges where one will do.  Use SE mode wherever possible.

--brian

-- 
Brian F. G. Bidulock
[email protected]
http://www.openss7.org/