一方で、予期しないものに寛容に振る舞う方針にはむしろシステムの堅牢さにとって有害な面がある、というポステルの法則（ロバストネス原則）の反省もある。
RFC 9413 - Maintaining Robust Protocols
https://www.rfc-editor.org/rfc/rfc9413
www.rfc-editor.orgRFC 9413: Maintaining Robust Protocols
The main goal of the networking standards process is to enable the long-term
interoperability of protocols. This document describes active protocol
maintenance, a means to accomplish that goal. By evolving specifications and
implementations, it is possible to reduce ambiguity over time and create a
healthy ecosystem.
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. However, it has been interpreted in a variety of ways.
While some interpretations help ensure the health of the Internet, others can
negatively affect interoperability over time. When a protocol is actively
maintained, protocol designers and implementers can avoid these pitfalls.
