The Harmful Consequences of the Robustness Principle
draft-iab-protocol-maintenance-04
Network Working Group M. Thomson
Internet-Draft Mozilla
Intended status: Informational November 04, 2019
Expires: May 7, 2020
The Harmful Consequences of the Robustness Principle
draft-iab-protocol-maintenance-04
Abstract
The robustness principle, often phrased as "be conservative in what
you send, and liberal in what you accept", has long guided the design
and implementation of Internet protocols. The posture this statement
advocates promotes interoperability in the short term, but can
negatively affect the protocol ecosystem over time. For a protocol
that is actively maintained, the robustness principle can, and
should, be avoided.
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This Internet-Draft will expire on May 7, 2020.
Thomson Expires May 7, 2020 [Page 1]
Internet-Draft Protocol Maintenance November 2019
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Fallibility of Specifications . . . . . . . . . . . . . . . . 3
3. Protocol Decay . . . . . . . . . . . . . . . . . . . . . . . 4
4. Ecosystem Effects . . . . . . . . . . . . . . . . . . . . . . 5
5. Active Protocol Maintenance . . . . . . . . . . . . . . . . . 6
6. Extensibility . . . . . . . . . . . . . . . . . . . . . . . . 8
7. Virtuous Intolerance . . . . . . . . . . . . . . . . . . . . 8
8. Exclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 9
9. Security Considerations . . . . . . . . . . . . . . . . . . . 10
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
11.1. Informative References . . . . . . . . . . . . . . . . . 10
11.2. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 12
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
The robustness principle has been hugely influential in shaping the
design of the Internet. As stated in IAB RFC 1958 [PRINCIPLES], the
robustness principle advises to:
Be strict when sending and tolerant when receiving.
Implementations must follow specifications precisely when sending
to the network, and tolerate faulty input from the network. When
in doubt, discard faulty input silently, without returning an
error message unless this is required by the specification.
This simple statement captures a significant concept in the design of
interoperable systems. Many consider the application of the
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robustness principle to be instrumental in the success of the
Internet as well as the design of interoperable protocols in general.
Time and experience shows that negative consequences to
interoperability accumulate over time if implementations apply the
robustness principle. This problem originates from an assumption
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