Path Signals

Document Type Replaced Internet-Draft (individual)
Author Ted Hardie 
Last updated 2018-04-19 (latest revision 2018-04-02)
Replaced by RFC 8558
Stream Internet Architecture Board (IAB)
Intended RFC status (None)
Expired & archived
pdf htmlized bibtex
Stream IAB state Replaced
Consensus Boilerplate Unknown
RFC Editor Note (None)

This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


This document discusses the nature of signals seen by on-path elements, 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. This document recommends that explict signals be used by transports which encrypt their state mechanics. It also recommends that a signal be exposed to the path only when the signal's originator intends that it be used by the network elements on the path.


Ted Hardie (

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)