Re: [p2pi] WG Action: Low Extra Delay Background Transport (ledbat)

[Stanislav Shalunov <[e-mail]>]

P.S. The URL to subscribe is https://www.ietf.org/mailman/listinfo/ledbat

On Nov 13, 2008, at 2:52 AM, Stanislav Shalunov wrote:

> LEDBAT was formerly known as TANA.  If you were subscribed, your  
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> interested, please consider subscribing to [e-mail].
>
> Thank you,  -- Stas
>
>
>
> Begin forwarded message:
>
>> From: IESG Secretary <[e-mail]>
>> Date: November 11, 2008 10:30:01 AM PST
>> To: [e-mail]
>> Cc: [e-mail], [e-mail], [e-mail]
>> Subject: WG Action: Low Extra Delay Background Transport (ledbat)
>>
>> A new IETF working group has been formed in the Transport Area.  For
>> additional information, please contact the Area Directors or the WG
>> Chairs.
>>
>> Low Extra Delay Background Transport (ledbat)
>> --------------------------------------------------------------
>> Current Status: Active Working Group
>>
>> Last Modified: 2008-11-06
>>
>> Chair(s):
>> * Stanislav Shalunov [[e-mail]]
>> * Murari Sridhavan [[e-mail]]
>>
>> Transport Area Director(s):
>> * Magnus Westerlund [[e-mail]]
>> * Lars Eggert [[e-mail]]
>>
>> Transport Area Advisor:
>> * Lars Eggert [[e-mail]]
>>
>> Mailing Lists:
>>
>> General Discussion: [e-mail]
>> To Subscribe: https://www.ietf.org/mailman/listinfo/ledbat
>> In Body: (un)subscribe
>> Archive: http://www.ietf.org/mail-archive/web/ledbat/
>>
>> Description of Working Group:
>>
>> The LEDBAT WG is chartered to standardize a congestion
>> control mechanism that should saturate the bottleneck,
>> maintain low delay, and yield to standard TCP.
>>
>> Applications that transmit large amounts of data for a long
>> time with congestion-limited TCP, but without AQM, fill the
>> buffer at the head of the bottleneck link. With FIFO queue,
>> this increases the delay experienced by other applications.
>> With buffer of one RTT, the delay doubles. In some cases,
>> the extra delay may be much larger. This is a particularly
>> acute and common case is when P2P applications upload over
>> thin home uplinks: delays in these cases can sometimes be of
>> the order of seconds.
>>
>> The IETF's standard end-to-end transport protocols have not
>> been designed to minimize the extra delay introduced by them
>> into the network. TCP, as a side effect of filling the
>> buffer until it experiences drop-tail loss, effectively
>> maximizes the delay. While this works well for applications
>> that are not delay-sensitive, it harms interactive
>> applications that share the same bottleneck. VoIP and games
>> are particularly affected, but even web browsing may become
>> problematic.
>>
>> LEDBAT is a transport-area WG that will focus on broadly
>> applicable techniques that allow large amounts of data to be
>> consistently transmitted without substantially affecting the
>> delays experienced by other users and applications.
>>
>> The WG will work on the following:
>>
>> (1) An experimental congestion control algorithm for
>> less-than-best-effort "background" transmissions, i.e., an
>> algorithm that attempts to scavenge otherwise idle bandwidth
>> for its transmissions in a way that minimizes interference
>> with regular best-effort traffic.
>>
>> Desired features of such an algorithm are:
>>
>> * saturate the bottleneck
>>
>> * eliminate long standing queues and thus keep
>> delay low when no other traffic is present
>>
>> * quickly yield to traffic sharing the same bottleneck queue
>> that uses standard TCP congestion control
>>
>> * add little to the queueing delays induced by TCP traffic
>>
>> * operate well in networks with FIFO queueing with drop-tail
>> discipline
>>
>> * be deployable for popular applications that currently
>> comprise noticeable fractions of Internet traffic
>>
>> * where available, use explicit congestion notification (ECN),
>> active queue management (AQM), and/or end-to-end
>> differentiated services (DiffServ).
>>
>> Application of this algorithm to existing transport
>> protocols (TCP, SCTP, DCCP) is expected to occur in the
>> working groups that maintain those protocols.
>>
>> Once experience is gained with this congestion control
>> algorithm on the Internet, the WG will consider if it is
>> appropriate to ask the IESG to advance the document as a
>> Proposed Standard.
>>
>> (2) A document that clarifies the current practices of
>> application design and reasons behind them and discusses the
>> tradeoffs surrounding the use of many concurrent TCP
>> connections to one destination and/or to different
>> destinations.
>>
>> Applications routinely open multiple TCP connections. For
>> example, P2P applications maintain connections to a number
>> of different peers while web browsers perform concurrent
>> downloads from the same web server. Application designers
>> pursue different goals when doing so: P2P apps need to
>> maintain a well-connected mesh in the swarm while web
>> browsers mainly use multiple connections to parallelize
>> requests that involve application latency on the web server
>> side. The IETF transport area community is concerned about
>> this practice, because standard Internet congestion control
>> results in different transport connections sharing
>> bottleneck capacity. When an application uses several
>> non-rate-limited transport connections to transfer through a
>> bottleneck, it may obtain a larger fraction of the
>> bottleneck than if it had used fewer connections. Although
>> capacity is the most commonly considered bottleneck
>> resource, middlebox state table entries are also an
>> important resource for an end system communication. Other
>> resource types may exist, and the guidelines are expected to
>> comprehensively discuss them.
>>
>> Applications use a variety of techniques to mitigate these
>> concerns. These techniques have not always been reviewed by
>> the IETF and their interaction with TCP dynamics is poorly
>> understood. The WG will document the known techniques,
>> discussing the consequences and, where appropriate, provide
>> guidance to application designers.
>>
>> Goals and Milestones:
>>
>> Oct 2009 Submit "Multiple Transport Connections in Applications  
>> Design"
>> to the IESG for consideration as an Informational RFC
>>
>> Oct 2009 Submit "Low Extra Delay Background Transport (LEDBAT)"
>> to the IESG for consideration as an Experimental RFC
>
> --
> Stanislav Shalunov
>
>
>

--
Stanislav Shalunov

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