Technical Summary
This document describes some of the open problems in Internet
congestion control that are known today. This includes several new
challenges that are becoming important as the network grows, as well
as some issues that have been known for many years. These challenges
are generally considered to be open research topics that may require
more study or application of innovative techniques before Internet-
scale solutions can be confidently engineered and deployed.
Working Group Summary
This document represents the work and the consensus of the ICCRG.
Personnel
Lars Eggert (lars.eggert@nokia.com) has reviewed this document for the IESG.
RFC Editor Note
(1) Replace beginning of Section 3.5.3 with:
3.5.3 Inelastic Multi-domain Pseudowires
Extending pseudo-wires across multiple domains poses specific issues.
Pseudowires (PW) [RFC3985] may carry non-TCP data flows (e.g. TDM
traffic or Constant Bit Rate (CBR) ATM traffic) over a multi-domain
IP network. Structure Agnostic TDM over Packet (SATOP) [RFC4553],
Circuit Emulation over Packet Switched Networks (CESoPSN), TDM over
IP, are not responsive to congestion control as discussed by
[RFC2914] (see also [RFC5033]). The same observation applies to ATM
circuit emulating services (CES) interconnecting CBR equipment (e.g.
PBX) across a Packet Switched Network (PSN).
Moreover, it is not possible to simply reduce the flow rate of a TDM
PW or an ATM PW when facing packet loss. Providers can rate control
corresponding incoming traffic but they may not be able to detect
that PWs carry TDM or CBR ATM traffic (mechanisms for characterizing
the traffic temporal properties may not necessarily be supported).
This can be illustrated with the following example.
(2) Add at the end of Section 3.8.4 Congestion Control in Multi-layered Networks
Section 3.5.3 deals with Inelastic Multi-domain Pseudowires (PW),
where the characteristics of the Pseudowire itself determines the
characteristics of the traffic crossing the multi-domain PSN
(and this independently of the characteristics of the traffic
carried in the PW). A more complex situation arises when inelastic
traffic is carried as part of a Pseudowire (e.g. inelastic traffic
over Ethernet PW over PSN) whose edges do not have the means to
characterize the properties of the traffic encapsulated into the
Ethernet frames. In this case, the problem explained in
Section 3.5.3 is not limited to multi-domain Pseudowires but more
generally induced by "Pseudowire carrying inelastic traffic" (over
a single- or multi-domain PSN). The problem becomes even more
intricated when the Ethernet PW carries both inelastic and
elastic traffic. Addressing this issue further comforts our
observation that a general framework to efficiently deal with
congestion control problems in multi-layer networks is absolutely
necessary but without harming its evolvability.