Subject: [Sigtran] M3UA DATA message parameters order

From: "Munnaluru, Krishna" <[email-masked]>
Date: Fri, 10 Feb 2006 09:42:53 -0600

Hi,

In section 3.2 the RFC3332 says:

"Where more than one parameter is included in a message, the parameters
may be in any order, except where explicitly mandated.  A receiver
SHOULD accept the parameters in any order."

In section 3.3.1 Payload Data Message (DATA) it says:

"The following format MUST be used for the Data Message:"

I am wondering if the MUST in section 3.3.1 mandates the order of the
parameters in the DATA message.  Other messages (for example DUNA) does
not have a MUST in it.

Could you please clarify?

Thanks,

Krishna

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From: Chris Benson <[email-masked]>
Date: Fri, 10 Feb 2006 08:53:40 -0800 (PST)

Krishna,

A certain ordering of parameters is required under RFC3332 
when the value of one parameter is needed to understand the 
context/syntax of another parameter.

For DATA messsages, it is explicitly mandated in 3.3.1 that:

"Where the optional Network Appearance parameter is present, 
it must be the first parameter in the message as it defines
the format of thes Protocol Data field."

Although it would be possible to implement by reading all
parameters first and then interpreting them, this is not
what the RFC specifies. The specific ordering statement
quoted above is one of the "explicitly mandated" exceptions
to the more general 3.2 paragraph you quoted. 

With thanks, from Chris Benson.