Coding and congestion control in transport
draft-irtf-nwcrg-coding-and-congestion-02
NWCRG N. Kuhn
Internet-Draft CNES
Intended status: Informational E. Lochin
Expires: September 6, 2020 ISAE-SUPAERO
F. Michel
UCLouvain
M. Welzl
University of Oslo
March 5, 2020
Coding and congestion control in transport
draft-irtf-nwcrg-coding-and-congestion-02
Abstract
FEC coding is a reliability mechanism that is distinct and separate
from the loss detection of congestion controls. Using FEC coding can
be a useful way to deal with transfer tail losses or with networks
having non-congestion losses. However, FEC coding mechanisms should
not hide congestion signals. This memo offers a discussion of how
FEC coding and congestion control can coexist. Another objective is
to encourage the research community to also consider congestion
control aspects when proposing and comparing FEC coding solutions in
communication systems.
This document is the product of the Coding for Efficient Network
Communications Research Group (NWCRG). The scope of the document is
end-to-end communications: FEC coding for tunnels is out-of-the scope
of the document.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 6, 2020.
Kuhn, et al. Expires September 6, 2020 [Page 1]
Internet-Draft Coding and congestion March 2020
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Separate channels, separate entities . . . . . . . . . . . . 3
3. FEC and CC layering . . . . . . . . . . . . . . . . . . . . . 5
3.1. FEC above the transport . . . . . . . . . . . . . . . . . 5
3.2. FEC within the transport . . . . . . . . . . . . . . . . 6
3.3. FEC below the transport . . . . . . . . . . . . . . . . . 7
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
7. Informative References . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
There are cases where deploying FEC coding improves the performance
of a transmission. As an example, it may take time for the sender to
detect transfer tail losses (losses that occur at the end of a
transfer, where e.g. TCP obtains no more ACKs to quickly repair the
loss via retransmission). This would improve the experience of
applications using short flows. Another example are networks where
non-congestion losses are persistent and prevent a sender from
exploiting the link capacity.
Coding is a reliability mechanism that is distinct and separate from
the loss detection of congestion controls. [RFC5681] defines TCP as
a loss-based congestion control; because FEC coding repairs such
losses, blindly applying it may easily lead to an implementation that
also hides a congestion signal to the sender. It is important to
ensure that such information hiding does not occur.
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