Re: [p2prg] Fwd: I-D Action:draft-irtf-p2prg-alto-survey-01.txt
Enrico Marocco <enrico.marocco@telecomitalia.it> Mon, 21 December 2009 16:24 UTC
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Date: Mon, 21 Dec 2009 17:23:37 +0100
From: Enrico Marocco <enrico.marocco@telecomitalia.it>
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To: Arnaud Legout <arnaud.legout@inria.fr>
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Subject: Re: [p2prg] Fwd: I-D Action:draft-irtf-p2prg-alto-survey-01.txt
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The agreed text is now in http://www.ietf.org/id/draft-irtf-p2prg-alto-survey-02.txt Enrico Arnaud Legout wrote: > Hi, > > I am fine with the text you propose, except that I would remove the sentence > "especially in networks with lower density of peers." I believe that it > is actually the opposite. > When there is a low density of peers, the locality policy will have few > impact on the overlay > interconnecting peers. > Find below a revised text. > > You are right that my points better fit into the mythbusting draft. > I will send you a proposition of text in a separate email. > > Thanks, > Arnaud. > > The literature presented in Section 2 shows that a certain level of > locality-awareness in the peer selection process of P2P algorithms is > usually beneficial to the application performance. However, an > excessive localization of the traffic might cause partitioning in > the overlay interconnecting peers, which will negatively affect > the performance experienced by the peers. > > Finding the right balance between localization and randomness in peer > selection is an open issue. At the time of writing, it seems that > different applications have different levels of tolerance and should > be addressed separately. Le Blond et al. [LeBlond] have studied the > specific case of BitTorrent, proposing a simple mechanism to prevent > partitioning in the overlay, yet reaching a high level of cross-domain > traffic reduction without adversely impacting peers. > > > > Enrico Marocco a écrit : >> Hi Arnoud, >> >> the work you mention is actually relevant to ALTO, but I'm not sure how >> to fit it in the survey part of the draft (that, in fact, is about >> proposed solutions). However, it deals with a relevant issue we did not >> mention, so what about adding the following text in a subsection of >> section 4? >> >> >> 4.6. Negative impact of over-localization >> >> The literature presented in Section 2 show that certain level of >> locality-awareness in the peer selection process of P2P algorithms is >> usually beneficial to the application performance. However, it seems >> reasonable to expect that an excessive impact of localization on such >> a process (to the detriment of randomness) will cause partitioning in >> overlay networks that will negatively affect the performance >> experienced by the users, especially in networks with lower density >> of peers. >> >> Finding the right balance between localization and randomness in peer >> selection is an open issue and, at the time of writing, it seems that >> different applications have different levels of tolerance and should >> be addressed separately. Le Blond et al. [LeBlond] have studied the >> specific case of BitTorrent, proposing a simple mechanism to prevent >> partitioning in the overlay, yet reaching high levels of cross-domain >> traffic reduction without adversely impacting peers. >> >> >> I'd rather avoid the details of how much traffic could be reduced >> according to your experience, as that's not really the goal of this >> document (it is actually mythbusting draft's goal). WDYT? >> >> Enrico >> >> Arnaud Legout wrote: >> >>> Hi, >>> >>> I believe that our work on "Pushing BitTorrent Locality to the Limit" >>> http://hal.inria.fr/inria-00343822/en/ >>> is highly relevant to ALTO. >>> Whereas we do not propose a new architecture, we perform a thorough >>> large scale evaluation using real world >>> data of the impact of locality. In particular, we answer two important >>> questions for ALTO. >>> >>> First, how much traffic can be kept local without adversely impacting >>> peers? Whatever the ALTO architecture is, >>> it will impact the structure of the overlay interconnecting peers. >>> We go much further than previous work on the understanding of the impact >>> of locality on the structure of that overlay. >>> In addition, reducing the amount of traffic that is kept local in order >>> to prevent partitions (thus a loss of performance for peers) >>> is the solution adopted by P4P and Ono. We introduce a simple mechanism >>> (that is backward compatible) to prevent partitions >>> and show that the traffic reduction on specific links can be >>> dramatically reduced by keeping more traffic local without adversely >>> impacting peers. Those kind of mechanisms are very important because >>> they enable to reap full benefits from the information >>> provided by ALTO. >>> >>> Second, what would be the benefit of a locality policy at the Internet >>> scale? >>> We show using a real world crawl of a large fraction of the all >>> BitTorrent peers that the benefit from deploying >>> a locality policy today would be a reduction of 40% on inter-AS links. >>> To the best of our knowledge, the work closer to ours is >>> the one of P4P. However, they only consider one torrent and one AS. >>> Whereas the P4P field tests are successfully used to support the relevance >>> of the P4P architecture, they cannot be used to support the relevance of >>> a locality policy at the scale of the Internet. But that last >>> point fundamental for the ALTO justification. A classical >>> argument (that we often faced before performing the large scale >>> BitTorrent measurement) is that at the scale of the Internet >>> the benefit of a locality policy will be negligible because there is on >>> average one or a few peers per AS. We show that even if >>> it is true that there is on average few peers per AS, the reduction of >>> traffic on inter-AS links that can be achieved using a locality >>> policy is still high at the Internet scale. Thus we believe that this is >>> the first large scale measurement that strongly support the relevance of the >>> ALTO effort. >>> >>> Finally, we do not claim that inter-AS links are always the right links >>> on which to perform traffic reduction, but that it is a reasonable first >>> level approximation. >>> >>> I hope those comments will help. >>> >>> Arnaud. >>> >>> stefano previdi a écrit : >>> >>>> Folks, >>>> >>>> the authors have submitted an updated version of alto-survey draft. >>>> Please, bring to the list your comments and we'll proceed with the >>>> publication process. >>>> >>>> Thanks. >>>> >>>> s. >>>> >>>> >>>> Begin forwarded message: >>>> >>>> >>>>> From: Internet-Drafts@ietf.org >>>>> Date: December 11, 2009 4:30:02 PM GMT+01:00 >>>>> To: i-d-announce@ietf.org >>>>> Subject: I-D Action:draft-irtf-p2prg-alto-survey-01.txt >>>>> Reply-To: internet-drafts@ietf.org >>>>> >>>>> A New Internet-Draft is available from the on-line Internet-Drafts >>>>> directories. >>>>> >>>>> Title : A Survey on Research on the Application-Layer >>>>> Traffic Optimization (ALTO) Problem >>>>> Author(s) : I. Rimac, et al. >>>>> Filename : draft-irtf-p2prg-alto-survey-01.txt >>>>> Pages : 17 >>>>> Date : 2009-12-11 >>>>> >>>>> A significant part of the Internet traffic today is generated by >>>>> peer-to-peer (P2P) applications used traditionally for file-sharing, >>>>> and more recently for real-time communications and live media >>>>> streaming. Such applications discover a route to each other through >>>>> an overlay network with little knowledge of the underlying network >>>>> topology. As a result, they may choose peers based on information >>>>> deduced from empirical measurements, which can lead to suboptimal >>>>> choices. This document, a product of the P2P Research Group, >>>>> presents a survey of existing literature on discovering and using >>>>> network topology information for application-layer traffic >>>>> optimization. >>>>> >>> _______________________________________________ >>> p2prg mailing list >>> p2prg@irtf.org >>> http://www.irtf.org/mailman/listinfo/p2prg
- [p2prg] Fwd: I-D Action:draft-irtf-p2prg-alto-sur… stefano previdi
- Re: [p2prg] Fwd: I-D Action:draft-irtf-p2prg-alto… Arnaud Legout
- Re: [p2prg] Fwd: I-D Action:draft-irtf-p2prg-alto… Enrico Marocco
- Re: [p2prg] Fwd: I-D Action:draft-irtf-p2prg-alto… Arnaud Legout
- Re: [p2prg] Fwd: I-D Action:draft-irtf-p2prg-alto… Enrico Marocco
- Re: [p2prg] Fwd: I-D Action:draft-irtf-p2prg-alto… Ivica Rimac
- Re: [p2prg] Fwd: I-D Action:draft-irtf-p2prg-alto… Enrico Marocco
- Re: [p2prg] Fwd: I-D Action:draft-irtf-p2prg-alto… stefano previdi