Subject: [NSIS] closing GIST issue 59 (D flag interpretation in MRI)

From: "Hancock, Robert" <[email-masked]>
Date: Thu, 1 Sep 2005 14:44:53 +0100

Dear all,

During the interoperability testing we discovered that the Direction
flag setting for the MRI was a significant 'gotcha', since there is
a natural tendency to think of the MRI as the Flow ID (and hence not
changing between upstream and downstream messages about the same
flow) whereas in fact it is Message Routing information (and hence
the D flag should be inverted). See also:

http://nsis.srmr.co.uk/cgi-bin/roundup.cgi/nsis-ntlp-issues/issue59

The text in 3.3 and 5.8.1.1 has been modified to highlight these facts,
with some minor changes elsewhere. Specifically, in 3.3, it describes
MRI as an aspect of message routing as follows:

   o  The format of the information that describes the path that the
      signalling should take, the Message Routing Information (MRI).
      For the path-coupled MRM, this is just the Flow Identifier (see
      Section 5.8.1.1) and some additional control information.
      Specifically, the MRI always includes a flag to distinguish
      between the two directions that signalling messages can take,
      denoted 'upstream' and 'downstream', and this flag would be
      inverted between a signalling message and its response.

and in 5.8.1.1:

                    ... A further flag in the MRI defines the
   direction of this particular signalling message relative to the flow
   described.  Therefore, for example, the flag would be inverted
   between a Query and Response message referring to the same flow.

Hoping this is *totally* unambiguous,

robert h.

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---

From: [email-masked]
Date: Fri, 2 Sep 2005 22:04:52 +0300

This seems reasonable. 

>-----Original Message-----
>From: [email-masked] [mailto:[email-masked]] On 
>Behalf Of ext Hancock, Robert
>Sent: 01 September, 2005 16:45
>To: [email-masked]
>Subject: [NSIS] closing GIST issue 59 (D flag interpretation in MRI)
>
>Dear all,
>
>During the interoperability testing we discovered that the 
>Direction flag setting for the MRI was a significant 'gotcha', 
>since there is a natural tendency to think of the MRI as the 
>Flow ID (and hence not changing between upstream and 
>downstream messages about the same
>flow) whereas in fact it is Message Routing information (and 
>hence the D flag should be inverted). See also:
>
>The text in 3.3 and 5.8.1.1 has been modified to highlight 
>these facts, with some minor changes elsewhere. Specifically, 
>in 3.3, it describes MRI as an aspect of message routing as follows:
>