Active Queue Management and Packet Scheduling

Document Charter Active Queue Management and Packet Scheduling WG (aqm)
Title Active Queue Management and Packet Scheduling
Last updated 2015-10-14
State Approved
WG State Concluded
IESG Responsible AD Mirja K├╝hlewind
Charter Edit AD Martin Stiemerling
Send notices to (None)


Internet routers, lower-layer switches, end-host operating
  systems, device drivers, and many types of additional
  middleboxes include memory buffers in which they implement
  queues to hold packets that require processing or otherwise
  need to wait for forwarding to the next hop.

  The queues are intended to absorb bursts of traffic that may
  naturally occur, and avoid unneccessary losses.  However, queues
  also cause latency and jitter in the eventual arrival times of
  packets.  This can create issues and complications for interactive

  Extremely large unmanaged buffers have been noticed in some
  software and equipment.  When these buffers start to fill,
  interactive applications and other traffic can be severely
  impacted or completely broken, due to high and potentially
  oscillating delays.
  The Active Queue Management and Packet Scheduling working group
  (AQM) works on algorithms for managing queues in order to:

  (1) minimize the length of standing queues, helping
  to reduce delay for interactive applications

  (2) help flow sources control their sending rates without
  unnecessary losses, e.g., through Explicit Congestion
  Notification (ECN)

  (3) consider the merits of various techniques to protect flows
  from negative impacts of other more aggressive or misbehaving

  (4) help avoid global synchronization of flows sharing a

  The AQM working group will produce documents that cover the
  design, use, configuration, and monitoring of algorithms for
  managing queues in Internet devices and software. The scope
  includes both how to best configure existing equipment and
  software, as well as recommendations on designing new equipment
  and software.

  The AQM working group will also publish algorithm specifications
  that are found to be broadly applicable and beneficial.  Evaluating
  these algorithms shall be done in coordination with the Internet
  Congestion Control Research Group (ICCRG), and related IETF Working 
  Groups, such as the RTP Media Congestion Avoidance Techniques Working 
  Group (RMCAT), in order to select and assess the relevant criteria, 
  scenarios, and metrics.

  The working group will also explore the merits of whether to
  isolate flows, and mechanisms for performing this function.  Note
  that isolation and potentially policing of flows implies some policy
  beyond what is required to simply minimize queues.  This topic
  requires significant attention in the working group.

  AQM algorithms do not have to be implemented universally in order
  to be effective.  Specifications will aid in producing proper
  implementations that avoid potential ambiguities and corner cases.
  "Interoperability" of algorithms and implementations of them is
  not the reason for creating these specifications; correctness is
  the primary motivation.
  The working group will not make changes to existing IETF protocols,
  but the working group may use Explicit Congestion Notification (ECN),
  Diffserv, and other mechanisms maintained by the TSVWG working group.
  Since the implementation of these mechanisms is likely to be entwined
  with AQM algorithms, there is expected to be close coordination
  between the TSVWG and AQM groups. 

  Many AQM algorithms have been proposed in academic literature, but
  a smaller number are widely implemented and deployed.  The goal of the
  working group is to produce recommendations that will actually be used,
  and algorithms that will actually be implemented, deployed in equipment,
  and enabled.  Towards these ends, the group actively encourages
  participation from operators and implementers. Furthermore, the group
  will jointly work with the Routing and Internet Area in order to
  involve vendors of networking equipment in the development of the
  AQM mechanisms. 

  Wider research and evaluation of AQM mechanisms shall be
  coordinated with the IRTF/ICCRG, and significant participation in this
  WG from the academic and research community is highly desirable, when
  it is directly relevant to implementation and deployment.
  Combined Queue Management / Packet Scheduling algorithms are in-scope, 
  provided their benefits have been evaluated against the established 
  requirements for an AQM algorithm. It is expected that some classes of 
  algorithms will focus on software implementations, while others on 
  existing or new hardware deployments, and algorithms may be specific 
  to distinct scenarios.