This is an announcement of an IETF-wide Call for Comment on draft-iab-path-signals-02. The document is being considered for publication as an Informational RFC within the IAB stream, and is available for inspection at: <https://datatracker.ietf.org/doc/draft-iab-path-signals/> The Call for Comment will last until 2018-12-25. Please send comments to architecture-discuss@ietf.org and iab@iab.org. Abstract This document discusses the nature of signals seen by on-path elements examining transport protocols, contrasting implicit and explicit signals. For example, TCP's state mechanics uses a series of well-known messages that are exchanged in the clear. Because these are visible to network elements on the path between the two nodes setting up the transport connection, they are often used as signals by those network elements. In transports that do not exchange these messages in the clear, on-path network elements lack those signals. Often, the removal of those signals is intended by those moving the messages to confidential channels. Where the endpoints desire that network elements along the path receive these signals, this document recommends explicit signals be used.
