RFCScope: Detecting Logical Ambiguities in Internet Protocol Specifications

Internet protocol specifications, published as Requests for Comments (RFCs) by the IETF organization, are essential to ensuring the interoperability, security, and reliability of the Internet. However, ambiguities in these specifications, particularly logical ambiguities such as inconsistencies and under-specifications, can lead to critical misinterpretations and implementation errors. Unfortunately, such ambiguities remain largely overlooked and challenging to detect with existing tools. In this paper, we present the first systematic study of verified technical errata from Standards Track RFCs over the past 11 years, identifying seven distinct subtypes of logical ambiguities. Building on these insights, we introduce RFCScope, the first scalable framework for detecting logical ambiguities in RFCs. RFCScope employs large language models (LLMs) through a modular pipeline that constructs targeted cross-document context, partitions specifications to preserve semantic integrity, applies bugtype-aware prompts for detection, and filters out false positives using structured reasoning validation. RFCScope uncovers 31 new logical ambiguities spanning all seven subtypes across 14 recent RFCs. Eight of these have been confirmed by RFC authors, with three officially verified as technical errata. Our results demonstrate that RFCScope offers a practical solution for improving the clarity, consistency, and reliability of protocol standards through ambiguity detection.