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"X-" Considered Harmful

Document type: Replaced Internet-Draft (individual)
Document stream: No stream defined
Last updated: 2014-07-02 (latest revision 2010-10-19)
Intended RFC status: Unknown
Other versions: (expired, archived): plain text, pdf, html

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IESG State: Replaced by draft-ietf-appsawg-xdash
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found here:


Many application protocols use named parameters to represent data (for example, header fields in Internet mail messages and HTTP requests). Historically, protocol designers and implementers have often differentiated between "standard" and "experimental" parameters by prefixing experimental parameters with the string "X-". This document argues that, on balance, the "X-" convention has more costs than benefits.


Peter Saint-Andre <>

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid)