Bret, 



Thanks for your response. I appreciate it. 


One follow up question on the following statements in RFC 3966: "If the 
reserved characters "+", ";", "=", and "?" are used as delimiters between 
components of the "tel" URI, they MUST NOT be percent encoded. These characters 
MUST be percent encoded if they appear in tel URI parameter values". 



Based on this, should the Tel URI be encoded as below for the  "cic" tel URI 
parameter, since "+" appears in the tel URI parameter value portion ? 



   Contact: < tel:+1-800-123-4567;cic=%2b1-6789 > 



I didn't see any specifics on this from RFC 4694 where the "cic" tel URI 
parameter is defined. 



Thanks, 

YoungSun 



----- Original Message -----


From: "Brett Tate" <[email protected]> 
To: [email protected], [email protected] 
Sent: Wednesday, March 6, 2013 12:35:49 PM 
Subject: RE: [Sip-implementors] Tel URI "+" encoding 

> In a Contact header of a SIP 302 response message 
> to be sent out , I am trying to include a tel URI 
> as below: 
> 
> Contact: < tel:+1-800-123-4567;cic=+1-6789 > 
> 
> But the third party SIP stack we use automatically 
> encode "+" to "%2b". 
> 
> Is this incorrect behavior? 

Yes. 

> Or is the SIP client receiving the tel URI supposed 
> to decode "%2b" as "+"? 

My understanding is no. 

The following RFC 3966 section 3 snippets appear to apply.  The '+' is being 
used as a delimiter; thus it "MUST NOT be percent encoded".  As far as I know, 
RFC 2396 indicating '+' within reserved indicates that the client should not 
interpret "%2b" as "+" within this situation. 

"The syntax definition follows RFC 2396 [RFC2396], indicating the 
 actual characters contained in the URI.  If the reserved characters 
 "+", ";", "=", and "?" are used as delimiters between components of 
 the "tel" URI, they MUST NOT be percent encoded.  These characters 
 MUST be percent encoded if they appear in tel URI parameter values. 

 Characters other than those in the "reserved" and "unsafe" sets (see 
 RFC 2396 [RFC2396]) are equivalent to their "% HEX HEX" percent 
 encoding." 

global-number-digits = "+" *phonedigit DIGIT *phonedigit 

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