Read the clarification alongside RFC 2119
01BCP means Best Current Practice. RFC 2119 defines requirement levels; RFC 8174 clarifies when its special key-word meanings apply.
Keep RFC 2119’s definitions and RFC 8174’s case rule. The boilerplate cites both; there is no RFC version 2.
Source for this drawing: RFC 8174 · Read RFC section 1 ↗
New to this? Start hereA quick picture + helpful background
A message needs an address.
Think of a packet as a small addressed envelope. Devices pass it onward; transport protocols decide what delivery promises an application gets.
Start with this guide; no earlier guide is needed for the overview.
These pictures are analogies to help you learn. The linked RFC explains the actual rules.
Terms in this drawing
- BCP 14
- Best Current Practice 14, the requirement-word convention documented by RFC 2119 together with RFC 8174.
- Normative text
- Text that specifies requirements, including plain prose or a format definition without a special key word.
- Conformance
- Meeting the applicable requirements of the specification.
Related RFCs and changes
“Updates” changes part of an earlier RFC. “Obsoletes” replaces it. This list shows selected related documents.
The updated guidance replaces often capitalized with all capitals and explicitly preserves normative text that uses no such key words.
Read the updated RFC section ↗An update changes a specific rule; it does not erase the earlier publication.
- RFC 2119 originally said the words are often capitalized. RFC 8174 replaces that introductory guidance with an all-capitals clarification.
- RFC 8174 updates RFC 2119; it does not obsolete it. The earlier definitions remain needed, read with the clarification.
- The recommended introductory wording cites BCP 14, RFC 2119 and RFC 8174 and says the special meanings apply when, and only when, the listed words appear in all capitals.
The current list is MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, SHOULD NOT, RECOMMENDED, NOT RECOMMENDED, MAY and OPTIONAL. RFC 8174 includes NOT RECOMMENDED in the boilerplate; RFC 2119 §4 already defines that synonym. This is a reading convention, not a new network protocol.
Read the RFC section ↗