[tsvwg] I-D Action: draft-ietf-tsvwg-ecn-l4s-id-14.txt

internet-drafts@ietf.org Tue, 09 March 2021 00:45 UTC

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Subject: [tsvwg] I-D Action: draft-ietf-tsvwg-ecn-l4s-id-14.txt
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A New Internet-Draft is available from the on-line Internet-Drafts directories.
This draft is a work item of the Transport Area Working Group WG of the IETF.

        Title           : Explicit Congestion Notification (ECN) Protocol for Ultra-Low Queuing Delay (L4S)
        Authors         : Koen De Schepper
                          Bob Briscoe
	Filename        : draft-ietf-tsvwg-ecn-l4s-id-14.txt
	Pages           : 59
	Date            : 2021-03-08

   This specification defines the protocol to be used for a new network
   service called low latency, low loss and scalable throughput (L4S).
   L4S uses an Explicit Congestion Notification (ECN) scheme at the IP
   layer that is similar to the original (or 'Classic') ECN approach,
   except as specified within.  'Classic' ECN marking is required to be
   equivalent to a drop, both when applied in the network and when
   responded to by a transport.  Unlike 'Classic' ECN marking, for
   packets carrying the L4S identifier, the network applies marking more
   immediately and more aggressively than drop, and the transport
   response to each mark is reduced and smoothed relative to that for
   drop.  The two changes counterbalance each other so that the
   throughput of an L4S flow will be roughly the same as a non-L4S flow
   under the same conditions.  Nonetheless, the much more frequent
   control signals and the finer responses to them result in much more
   fine-grained adjustments, so that ultra-low and consistently low
   queuing delay (typically sub-millisecond on average) becomes possible
   for L4S traffic without compromising link utilization.  Thus even
   capacity-seeking (TCP-like) traffic can have high bandwidth and very
   low delay at the same time, even during periods of high traffic load.

   The L4S identifier defined in this document distinguishes L4S from
   'Classic' (e.g. TCP-Reno-friendly) traffic.  It gives an incremental
   migration path so that suitably modified network bottlenecks can
   distinguish and isolate existing traffic that still follows the
   Classic behaviour, to prevent it degrading the low queuing delay and
   low loss of L4S traffic.  This specification defines the rules that
   L4S transports and network elements need to follow to ensure they
   neither harm each other's performance nor that of Classic traffic.
   Examples of new active queue management (AQM) marking algorithms and
   examples of new transports (whether TCP-like or real-time) are
   specified separately.

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