Subject: rfc2327 inconsistency//Special characters in SDP

From: Rajesh Kumar <[email-masked]>
Date: Tue, 24 Oct 2000 15:41:53 -0700

Dear Mark Handley / Van Jocobson / MMUSIC chair,

I seem to have found an inconsistency in the rfc2327 ABNF, which, 
paradoxically makes my job of defining ATM conventions for SDP simpler!. 
Perhaps, someone (the authors?) could guide me in this regard.

The definition of 'alpha-numeric' in the rfc2327 ABNF excludes special 
characters such as $, / and -. These are included in the definition of 'safe'.

alpha-numeric =       ALPHA | DIGIT
safe =                alpha-numeric |
                          "'" | "'" | "-" | "." | "/" | ":" | "?" | """ |
                          "#" | "$" | "&" | "*" | ";" | "=" | "@" | "[" |
                          "]" | "^" | "_" | "`" | "{" | "|" | "}" | "+" |
                          "~" | "

Most of the SDP parameters are defined as 1*(alpha-numeric). Thus, 'proto' 
which is defined as 1*(alpha-numeric) should not have the "/" character, 
but it does as in RTP/AVP!

I really think that special characters should be allowed in many of these 
values, and that these definitions 1*(alpha-numeric) should be altered to 
1*(safe).

The reason why I am so interested in this is that in my conventions for SDP 
in the ATM context, I have extensively used special characters such as "/", 
"$" and "-" and I do not want to be forced to replace them with reserved 
strings such as "CHOOSE" for "$". I think that SDP ABNF syntax is 
inconsistent on this point, and I should be allowed to re-define many of 
these fields as 1*(safe) rather than 1*(alpha-numeric) for the ATM case.

I do not think there is a good reason for precluding my use of these 
special characters in the ATM conventions for SDP, since rfc2327 flouts its 
own BNF definition in this regard.

So it is 1*(safe) then in the document that will replace rfc2327?

Comments?

Rajesh Kumar
Cisco Systems