Re: Notices to ASPTM message mapping

Kolomaznik,

Kolomaznik Jan wrote:                                                           (Mon, 29 May 2006 13:16:15)
> 
>    Hello,
> 
>    I  would like to share any findings we have made during implementation
>    of  SUA  in  IPSP environment. Our work has been based on RFC 3868 and
>    draft-ietf-sigtran-sua-implementor-guide-03.txt.  Please send comments
>    if you find out we are not true.
> 
> 
>    1)  Problem  with  mapping  of  ASPTM messages on SCTP stream. - Which
>    stream  number  to  use?  ... there are two relevant paragraphs in RFC
>    3868, sua-implementor-guide-03 does not solve this question.
> 
>    RFC 3868, section 4.2.1:
> 
>    "All non-Transfer messages, with the exception of ASPTM, BEAT and BEAT
>    Ack messages SHOULD be sent on SCTP stream '0'.  ASPTM messages MAY be
>    sent  on  one of the streams used to carry data traffic related to the
>    Routing Context(s), to minimize possible message loss."
> 
>    RFC 3868, section 4.3.4.3:
> 
>    "It  is possible for the ASP to receive Data message(s) before the ASP
>    Active  Ack message as the ASP Active Ack and Data messages from an SG
>    or  IPSP  may  be  sent  on  different  SCTP streams.  Message loss is
>    possible,  as the ASP does not consider itself in the ASP-ACTIVE state
>    until reception of the ASP Active Ack message."
> 
> 
>    So  ASPTM messages MAY be sent on any SCTP stream, but generally it is
>    better  to  send they on any traffic stream (not on SCTP stream 0). It
>    practically means, a sending entity MAY send it on any SCTP stream and
>    a  receiving  entity  SHOULD  be  prepared  to  receive it on any SCTP
>    stream.

Yes.  In general, an implementation should be prepared to receive any message
on any stream.

> 
> 
>    2)  Mapping  of  ASPTM  Ack  messages on SCTP stream ... I think it is
>    general  principle  to  be  received  message acknowledged on the same
>    stream as an acknowledged message has been received - but this general
>    principle is not enforced in RFC 3868 or
>    sigtran-sua-implementor-guide-03.  This  situation  may  leads  to the
>    situation following the next example:
> 
>    ------------ ASP Active/SCTP stream 1 ----->
> 
>    <-------- ASP Active Ack/SCTP stream 0 ----

Yes, that is possible.  Did you see any reason why it would be necessary to
restrict the situtation further?

--brian

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