Re: [ppsp] PPSP distributed tracker

[Johan Pouwelse <[e-mail]>]

Dear PPSP,
Just completed a review of V3 of your distributed tracker proposal.

Main point:
As indicated my me before within PPSP, light-weight solutions are not often
proposed here. This proposal leans towards overengineering.

This proposal does not make a distinction between tracker replication
and distribution using PEX or DHT. By having multiple central
trackers, reliability should improve. However, how many seconds does a
peer wait when a query gets no reply? If a peer waits for 10 seconds
before trying a secondairy peers the result is significant loss of
user experienced performance and degradation of streaming service.
Should a peer issue multiple request in parallel to ensure fast
performance at the cost of server resources? From my viewpoint a PPSP
standard should recommend policies here. You agree?

Section 2 defines six different entities/roles, where 2 is the
minimum. By expanding the tracker functionality to include network
locality, piece availability registration and a tracker2tracker
protocol we risk defining a standard which cannot be implemented,
scale or compete with the performance of minimalistic solutions.
Missing from this draft is the handling of NATed peers. Does the
tracker do a simple dialback to check if a peer is connectable? Is
connectability part of peer info?

For over 10 years the Bittorrent tracker protocol seems to be doing
well. This proposal is a radical departure from this deployed
technology. An explanation why this is done would significantly
improve this draft in my opinion. Is that possible?

 Greetings, johan.
On 25/10/2011, Xiao, Lin (NSN - CN/Beijing) <[e-mail]> wrote:
> Hi,
>
>
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> As I said, I made another version to give a clearer description. Also the
> Figures and the flows are modified accordingly.
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> http://tools.ietf.org/id/draft-xiao-ppsp-reload-distributed-tracker-03.txt
>
>
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> BR
>
> Xiao Lin
>
>
>
> From: [e-mail] [mailto:[e-mail]] On Behalf Of
> Xiao, Lin (NSN - CN/Beijing)
> Sent: Tuesday, October 25, 2011 4:12 PM
> To: ext Yingjie Gu(yingjie); [e-mail]
> Subject: Re: [ppsp] PPSP distributed tracker
>
>
>
> Hi Yingjie,
>
>
>
> I’ve answered your questions as followed.
>
> By the way, I’m submitting a updated version 03, which may describe the
> change more clearly.
>
>
>
> BR
>
> Xiao Lin
>
>
>
> From: ext Yingjie Gu(yingjie) [mailto:[e-mail]]
> Sent: Tuesday, October 25, 2011 3:41 PM
> To: Xiao, Lin (NSN - CN/Beijing); [e-mail]
> Subject: 答复: [ppsp] PPSP distributed tracker
>
>
>
> Thanks to Lin  again for doing all the work.
>
> I would apologize, as co-author, I failed to contribute to this version of
> updating.
>
> Here is my comments and hope it can help.
>
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> ________________________________
>
> Best Regards
> Gu Yingjie
>
>
>
> 发件人: Xiao, Lin (NSN - CN/Beijing) [mailto:[e-mail]]
> 发送时间: 2011年10月25日 乐乐14:41
> 收件人: ext Yingjie Gu(yingjie); [e-mail]
> 主题: RE: [ppsp] PPSP distributed tracker
>
>
>
> The updating content in v02 includes :
>
>
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> l  The local tracker can keep the content record of  local peers, at the
> same time when it forwards the  content update/registration information to
> tracker overlay. So, most content requests can be solved locally.
>
> Y.J. Gu :  How frequently the content record is shared among trackers?  I
> guess not real-time sharing, because the content record is updated quite
> often.  It could be an implementation choice, but we can give some advise in
> the draft.
>
> [Lin]: content record is not shared among trackers, it only stored in both
> local connection tracker (for traffic localization) and the responsible
> swarm tracker located by RELOAD mechanism (maintains overall peerlist for a
> swarm).
>
>
>
> l  Delete  the open issues in chapter 5, and decide to use local connection
> tracker to manage the status of the ppsp peers locally, as most peer
> requests are from local peers according to the algorithm mentioned above. If
> the peer status can not be found in local connection tracker, the request is
> forwarded to the tracker overlay, as each local tracker always registries
> its own address to a node on tracker overly, whose ID has a DHT mapping
> with the PPSP peer. As the position of the peer status , which is also the
> peer’s connection node address, is always registered to the tracker overlay
> according to RELOAD.
>
> Y.J. Gu : Why not share peer status when you share content record? The
> reason that we share content record among trackers is to decrease the
> response time to a request for some content that is not locally stored. If
> the content can be found locally, but the tracker still have to find the
> status through the overlay, it doesn’t decrease the response time. The
> status shared on tracker overlay might not be accurate, but neither do the
> content record. It’s only a way to improve the performance. The peer, who
> get an inaccurate information from the tracker, can correct it by
> communicating with the peers in peerlist. Even the local connection tracker
> can not promise an accurate content record and peer status.
>
> [Lin]:   No. I mean, node status always maintained by its local connection
> tracker, but only put the information that how to find the local connection
> tracker of the peer (the position of the peer status) on the tracker
> overlay.  So, the frequent status updates can be done locally, but there
> must be a way (by RELOAD overlay ) to find the position of the status
> information, and the position information do not need frequent updates,
> which saves the traffic across overlay.
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> l  A data kind for peerStatusIndex is defined.
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> As still some editorial errors, I’ll give a new version soon.
>
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> BR
>
> Xiao Lin
>
>
>
> From: ext Yingjie Gu(yingjie) [mailto:[e-mail]]
> Sent: Tuesday, October 25, 2011 11:35 AM
> To: Xiao, Lin (NSN - CN/Beijing); [e-mail]
> Subject: 答复: [ppsp] PPSP distributed tracker
>
>
>
> Thanks lin for updating the draft.
>
> Maybe it’s better to give a brief introduction of the updating from -01
> version to -02 version.
>
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>
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> ________________________________
>
> Best Regards
> Gu Yingjie
>
>
>
> 发件人: [e-mail] [mailto:[e-mail]] 代表 Xiao, Lin (NSN
> - CN/Beijing)
> 发送时间: 2011年10月25日 乐乐11:19
> 收件人: [e-mail]
> 主题: [ppsp] PPSP distributed tracker
>
>
>
> Hi All,
>
>
>
> I’ve updated the distributed tracker draft for a while. Could you please
> give your comment on it ? Thanks!
>
>
>
> http://tools.ietf.org/id/draft-xiao-ppsp-reload-distributed-tracker-02.txt
>
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> Abstract
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> This document defines PPSP tracker usages for REsource LOcation And
>
> Discovery (RELOAD).  Although PPSP assumes a centralized tracker from
>
> peer's point of view, the logical centralized tracker could be realized
>
> by a cluster of geographically distributed trackers. In this draft, we
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> design distributed trackers system, which are organized by RELOAD. It
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> provides lookup service for file/channel indexes and Peer Status among
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> the distributed trackers.
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> BR
>
> Xiao Lin
>
>