Draft: draft-irtf-nwcrg-coding-and-congestion-08

Commentary: A few small suggestions , but otherwise great , thanks for doing this !
fig:fec-below presents an architecture where FEC is applied end-to-
end below the transport layer, but above the link layer.  Note that
it is common to apply FEC at the link layer, where it contributes to
the total capacity that a link exposes to upper layers.  This
application of FEC is out of scope of this document.  In the scenario
considered here, the repair symbols are sent on top of what is
allowed by the congestion control.
fig:fec-below presents an architecture where FEC is applied end-to-
end below the transport layer, but above the link layer.  Note that
it is common to apply FEC at the link layer, where it contributes to
the total capacity that a link exposes to upper layers.  This
application of FEC is out of scope of this document.  This includes
the use of FEC on top of a link layer in scenarios where the link is
known by configuration.  In the scenario considered here, the repair
symbols are sent on top of what is allowed by the congestion control.
Some existing solutions already propose to disambiguate acked packets
from rebuilt packets QUIC-FEC.  New signaling methods and FEC-
recovery-aware congestion controls could be proposed.
Some existing solutions already propose to disambiguate acked packets
from rebuilt packets QUIC-FEC.  New signaling methods and FEC-
recovery-aware congestion controls could be proposed.  This would
allow the design of adaptive coding rates.
Our advice is that new research contributions should be mapped
following the organization of this document.  Otherwise, this may
lead to wrong assumptions on the validity of the proposal and wrong
ideas about the relevance of coding for a given use case.
The discussion provided in this document aims to encourage the
research community to also consider congestion control aspects when
proposing and comparing FEC coding solutions in communication
systems.  As one example, this draft proposes discussions on the
impact of the proposed FEC solution on congestion control, especially
loss-based congestion control mechanisms.  When a research work aims
at improving throughput by hiding the packet loss signal from
congestion control, the authors should 1) discuss the advantages of
using the proposed FEC solution compared to replacing the congestion
control by one that ignores a portion of the encountered losses, 2)
critically discuss the impact of hiding packet loss from the
congestion control mechanism.
Research Recommendation 1: From a congestion control point-of-view, a
repaired packet must be considered as a lost packet.  This does not
apply to the usage of FEC on a path that is known to be lossy.
Research Recommendation 2: New research contributions should be
mapped following the organization of this document (above, below, in
the congestion control) and should consider congestion control
aspects when proposing and comparing FEC coding solutions in
communication systems.
Research Recommendation 3: When a research work aims at improving
throughput by hiding the packet loss signal from congestion control
(e.g., because the path between the sender and receiver is known to
consist of a noisy wireless link), the authors should 1) discuss the
advantages of using the proposed FEC solution compared to replacing
the congestion control by one that ignores a portion of the
encountered losses, 2) critically discuss the impact of hiding packet
loss from the congestion control mechanism.