Subject: RFC 3261 ambiguity

From: Marco Ambu <[email-masked]>
Date: Wed, 11 Jan 2006 10:40:09 +0100

Dear all,
I would like to show you an ambiguity in RFC 3261.
The ABNF for SIP in RFC 3261 page 227 defines header Accept as "Accept = 
"Accept" HCOLON [accept-range *(COMMA accept-range)].
Expanding this form we have:
Accept = "Accept" HCOLON [( (...) *(SEMI m-parameter) *(SEMI 
accept-param) ) *(COMMA accept-range)]
For example we can have
Accept: 
application/sdp;m_extension_parameter=value1;accept_extension_param=value2;q=0.5
We know from RFC 3261 that q is an accept-param.
We don't know how to consider the first two unknown parameters: how to 
distinguish from m-parameter and accept-param?

While in ohter cases RFC 3261 shows the rules to solve ambiguities (for 
example how to consider the parameters in a Contact URI if the URI is 
not enclosed in angular brakets) I have not found any suggestion for 
this specific case in RFC 3261.

Best Regards,
Marco Ambu
Abbeynet