IESG Statement: Normative and Informative References

19 Apr 2006

Nearly all RFCs contain citations to other documents, and these are listed in a References section near the end of the RFC.

There are many styles for references, and the RFCs have one of their own. Please follow the reference style used in recent RFCs. Please note that for documents that have been assigned an STD or BCP number, the number must be included in the reference. 

Within an RFC, references to other documents fall into two general categories: "normative" and "informative". Normative references specify documents that must be read to understand or implement the technology in the new RFC, or whose technology must be present for the technology in the new RFC to work. An informative reference is not normative; rather, it only provides additional information. For example, an informative reference might provide background or historical information. Informative references are not required to implement the technology in the RFC. 

Note 1: Even references that are relevant only for optional features must be classified as normative if they meet the above conditions for normative references. 

Note 2: It is not considered necessary to cite basic specifications that may be safely assumed to be known to practitioners (for example, RFC 791 need not be cited in every specification that mentions IPv4). 

Note 3: The normative/informative distinction is relevant in any document that amounts to a technical specification, even if its intended status is Experimental or Informational. 

Note 4: Normative references in RFCs cannot be to "work in progress" documents such as Internet Drafts. Drafts with such references will not be published as RFCs until the references are also published. 

The distinction between normative and informative references is often important. The IETF standards process according to RFC 2026 and RFC 3967, and the RFC Editor publication process, both need to know whether a reference to a work in progress is normative. An RFC cannot be published until all of the documents that it lists as normative references have been published. In practice, this often results in the simultaneous publication of a group of interrelated RFCs. 

For these reasons, the IESG and the RFC Editor have established guidelines that will request separate reference lists for normative and informative references in Internet Drafts and RFCs. For example, if both types are present, there would be two reference subsections, numbered s.1 and s.2 for example: 

s.1. Normative References

xxx
... 
xxx

s.2. Informative References

xxx
...
xxx

Of course, if there is only one type of reference, only one section is needed.