Long-term Viability of Protocol Extension Mechanisms
draft-iab-use-it-or-lose-it-00
Network Working Group M. Thomson
Internet-Draft Mozilla
Intended status: Informational July 30, 2019
Expires: January 31, 2020
Long-term Viability of Protocol Extension Mechanisms
draft-iab-use-it-or-lose-it-00
Abstract
The ability to change protocols depends on exercising the extension
and version negotiation mechanisms that support change. Protocols
that don't use these mechanisms can find that deploying changes can
be difficult and costly.
Status of This Memo
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This Internet-Draft will expire on January 31, 2020.
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Thomson Expires January 31, 2020 [Page 1]
Internet-Draft Use It Or Lose It July 2019
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Implementations of Protocols are Imperfect . . . . . . . . . 3
2.1. Good Protocol Design is Not Itself Sufficient . . . . . . 3
2.2. Examples of Disuse . . . . . . . . . . . . . . . . . . . 4
2.3. Multi-Party Interactions and Middleboxes . . . . . . . . 5
3. Retaining Viable Protocol Evolution Mechanisms . . . . . . . 6
3.1. Examples of Active Use . . . . . . . . . . . . . . . . . 7
3.2. Dependency is Better . . . . . . . . . . . . . . . . . . 7
3.3. Unused Extension Points Become Unusable . . . . . . . . . 8
4. Defensive Design Principles for Protocols . . . . . . . . . . 9
4.1. Active Use . . . . . . . . . . . . . . . . . . . . . . . 9
4.2. Cryptography . . . . . . . . . . . . . . . . . . . . . . 9
4.3. Grease . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.4. Invariants . . . . . . . . . . . . . . . . . . . . . . . 11
4.5. Effective Feedback . . . . . . . . . . . . . . . . . . . 11
5. Security Considerations . . . . . . . . . . . . . . . . . . . 12
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
7. Informative References . . . . . . . . . . . . . . . . . . . 12
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 16
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction
A successful protocol [SUCCESS] will change in ways that allow it to
continue to fulfill the needs of its users. New use cases,
conditions and constraints on the deployment of a protocol can render
a protocol that does not change obsolete.
Usage patterns and requirements for a protocol shift over time. In
response, implementations might adjust usage patterns within the
constraints of the protocol, the protocol could be extended, or a
replacement protocol might be developed. Experience with Internet-
scale protocol deployment shows that each option comes with different
costs. [TRANSITIONS] examines the problem of protocol evolution more
broadly.
This document examines the specific conditions that determine whether
protocol maintainers have the ability to design and deploy new or
modified protocols. Section 2 highlights some historical issues with
difficulties in transitions to new protocol features. Section 3
argues that ossified protocols are more difficult to update and
successful protocols make frequent use of new extensions and code-
points. Section 4 outlines several strategies that might aid in
ensuring that protocol changes remain possible over time.
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