> -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of > Andrew Kohlsmith > Sent: Saturday, June 11, 2005 11:58 AM > To: asterisk-users@lists.digium.com > Subject: Re: [Asterisk-Users] ATTN: Keith > > On Saturday 11 June 2005 11:35, Tracy Phillips wrote: > > > That is *precisely* why the RFC is worded "should" -- it is > > > optional. If the RFC said "must" then it is required. RFCs are > > > worded very carefully as a general rule. > > > I am just glad everyone doesn't have that attitude about RFCs. > > I'm not sure I understand -- I'm not making this up, RFCs use > "must" and "should" very carefully. The latter is a > guideline, and the former is a rule. I'm trying to find the > link describing this but it's eluding me at the moment. > > I think this is a VERY good thing; RFCs are like the laws of > the internet; they should not be open to interpretation since > they define the protocols used to interoperate. > > -A.
Andrew, Did some looking for you. It is contained in RFC 2119, Key words for use in RFCs to Indicate Requirement Levels. Here is an excerpt: Abstract In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. Authors who follow these guidelines should incorporate this phrase near the beginning of their document: The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119. Note that the force of these words is modified by the requirement level of the document in which they are used. 1. MUST This word, or the terms "REQUIRED" or "SHALL", mean that the definition is an absolute requirement of the specification. 2. MUST NOT This phrase, or the phrase "SHALL NOT", mean that the definition is an absolute prohibition of the specification. 3. SHOULD This word, or the adjective "RECOMMENDED", mean that there may exist valid reasons in particular circumstances to ignore a particular item, but the full implications must be understood and carefully weighed before choosing a different course. 4. SHOULD NOT This phrase, or the phrase "NOT RECOMMENDED" mean that there may exist valid reasons in particular circumstances when the particular behavior is acceptable or even useful, but the full implications should be understood and the case carefully weighed before implementing any behavior described with this label. 5. MAY This word, or the adjective "OPTIONAL", mean that an item is truly optional. One vendor may choose to include the item because a particular marketplace requires it or because the vendor feels that it enhances the product while another vendor may omit the same item. An implementation which does not include a particular option MUST be prepared to interoperate with another implementation which does include the option, though perhaps with reduced functionality. In the same vein an implementation which does include a particular option MUST be prepared to interoperate with another implementation which does not include the option (except, of course, for the feature the option provides.) 6. Guidance in the use of these Imperatives Imperatives of the type defined in this memo must be used with care and sparingly. In particular, they MUST only be used where it is actually required for interoperation or to limit behavior which has potential for causing harm (e.g., limiting retransmisssions) For example, they must not be used to try to impose a particular method on implementors where the method is not required for interoperability. So here you are absolutely correct. Robert _______________________________________________ Asterisk-Users mailing list Asterisk-Users@lists.digium.com http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users