From: Olaoluwa Osuntokun <laolu32@gmail•com>
To: Arnoud Kouwenhoven - Pukaki Corp via bitcoin-dev
<bitcoin-dev@lists•linuxfoundation.org>
Subject: Re: [bitcoin-dev] BIP Proposal: Compact Client Side Filtering for Light Clients
Date: Fri, 09 Jun 2017 03:59:17 +0000 [thread overview]
Message-ID: <CAO3Pvs8-GAwUNZ9Fc7DAb9ZCwP4p5Wh0sD1O0n5NSLVcY2nJtg@mail.gmail.com> (raw)
In-Reply-To: <CAO3Pvs-nNQR_53_wjS4rPU8W20kePnrSdBvCXMwpaOG7gpUNJQ@mail.gmail.com>
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Hi y'all,
Thanks for all the comments so far!
I've pushed a series of updates to the text of the BIP repo linked in the
OP.
The fixes include: typos, components of the specification which were
incorrect
(N is the total number of items, NOT the number of txns in the block), and a
few sections have been clarified.
The latest version also includes a set of test vectors (as CSV files), which
for a series of fp rates (1/2 to 1/2^32) includes (for 6 testnet blocks,
one of
which generates a "null" filter):
* The block height
* The block hash
* The raw block itself
* The previous basic+extended filter header
* The basic+extended filter header for the block
* The basic+extended filter for the block
The size of the test vectors was too large to include in-line within the
document, so we put them temporarily in a distinct folder [1]. The code
used to
generate the test vectors has also been included.
-- Laolu
[1]: https://github.com/Roasbeef/bips/tree/master/gcs_light_client
On Thu, Jun 1, 2017 at 9:49 PM Olaoluwa Osuntokun <laolu32@gmail•com> wrote:
> > In order to consider the average+median filter sizes in a world worth
> larger
> > blocks, I also ran the index for testnet:
> >
> > * total size: 2753238530
> > * total avg: 5918.95736054141
> > * total median: 60202
> > * total max: 74983
> > * regular size: 1165148878
> > * regular avg: 2504.856172982827
> > * regular median: 24812
> > * regular max: 64554
> > * extended size: 1588089652
> > * extended avg: 3414.1011875585823
> > * extended median: 35260
> > * extended max: 41731
> >
>
> Oops, realized I made a mistake. These are the stats for Feb 2016 until
> about a
> month ago (since height 400k iirc).
>
> -- Laolu
>
>
> On Thu, Jun 1, 2017 at 12:01 PM Olaoluwa Osuntokun <laolu32@gmail•com>
> wrote:
>
>> Hi y'all,
>>
>> Alex Akselrod and I would like to propose a new light client BIP for
>> consideration:
>> *
>> https://github.com/Roasbeef/bips/blob/master/gcs_light_client.mediawiki
>>
>> This BIP proposal describes a concrete specification (along with a
>> reference implementations[1][2][3]) for the much discussed client-side
>> filtering reversal of BIP-37. The precise details are described in the
>> BIP, but as a summary: we've implemented a new light-client mode that uses
>> client-side filtering based off of Golomb-Rice coded sets. Full-nodes
>> maintain an additional index of the chain, and serve this compact filter
>> (the index) to light clients which request them. Light clients then fetch
>> these filters, query the locally and _maybe_ fetch the block if a relevant
>> item matches. The cool part is that blocks can be fetched from _any_
>> source, once the light client deems it necessary. Our primary motivation
>> for this work was enabling a light client mode for lnd[4] in order to
>> support a more light-weight back end paving the way for the usage of
>> Lightning on mobile phones and other devices. We've integrated neutrino
>> as a back end for lnd, and will be making the updated code public very
>> soon.
>>
>> One specific area we'd like feedback on is the parameter selection. Unlike
>> BIP-37 which allows clients to dynamically tune their false positive rate,
>> our proposal uses a _fixed_ false-positive. Within the document, it's
>> currently specified as P = 1/2^20. We've done a bit of analysis and
>> optimization attempting to optimize the following sum:
>> filter_download_bandwidth + expected_block_false_positive_bandwidth. Alex
>> has made a JS calculator that allows y'all to explore the affect of
>> tweaking the false positive rate in addition to the following variables:
>> the number of items the wallet is scanning for, the size of the blocks,
>> number of blocks fetched, and the size of the filters themselves. The
>> calculator calculates the expected bandwidth utilization using the CDF of
>> the Geometric Distribution. The calculator can be found here:
>> https://aakselrod.github.io/gcs_calc.html. Alex also has an empirical
>> script he's been running on actual data, and the results seem to match up
>> rather nicely.
>>
>> We we're excited to see that Karl Johan Alm (kallewoof) has done some
>> (rather extensive!) analysis of his own, focusing on a distinct encoding
>> type [5]. I haven't had the time yet to dig into his report yet, but I
>> think I've read enough to extract the key difference in our encodings: his
>> filters use a binomial encoding _directly_ on the filter contents, will we
>> instead create a Golomb-Coded set with the contents being _hashes_ (we use
>> siphash) of the filter items.
>>
>> Using a fixed fp=20, I have some stats detailing the total index size, as
>> well as averages for both mainnet and testnet. For mainnet, using the
>> filter contents as currently described in the BIP (basic + extended), the
>> total size of the index comes out to 6.9GB. The break down is as follows:
>>
>> * total size: 6976047156
>> * total avg: 14997.220622758816
>> * total median: 3801
>> * total max: 79155
>> * regular size: 3117183743
>> * regular avg: 6701.372750217131
>> * regular median: 1734
>> * regular max: 67533
>> * extended size: 3858863413 <(385)%20886-3413>
>> * extended avg: 8295.847872541684
>> * extended median: 2041
>> * extended max: 52508
>>
>> In order to consider the average+median filter sizes in a world worth
>> larger blocks, I also ran the index for testnet:
>>
>> * total size: 2753238530
>> * total avg: 5918.95736054141
>> * total median: 60202
>> * total max: 74983
>> * regular size: 1165148878
>> * regular avg: 2504.856172982827
>> * regular median: 24812
>> * regular max: 64554
>> * extended size: 1588089652
>> * extended avg: 3414.1011875585823
>> * extended median: 35260
>> * extended max: 41731
>>
>> Finally, here are the testnet stats which take into account the increase
>> in the maximum filter size due to segwit's block-size increase. The max
>> filter sizes are a bit larger due to some of the habitual blocks I
>> created last year when testing segwit (transactions with 30k inputs, 30k
>> outputs, etc).
>>
>> * total size: 585087597
>> * total avg: 520.8839608674402
>> * total median: 20
>> * total max: 164598
>> * regular size: 299325029
>> * regular avg: 266.4790836307566
>> * regular median: 13
>> * regular max: 164583
>> * extended size: 285762568
>> * extended avg: 254.4048772366836
>> * extended median: 7
>> * extended max: 127631
>>
>> For those that are interested in the raw data, I've uploaded a CSV file
>> of raw data for each block (mainnet + testnet), which can be found here:
>> * mainnet: (14MB):
>> https://www.dropbox.com/s/4yk2u8dj06njbuv/mainnet-gcs-stats.csv?dl=0
>> * testnet: (25MB):
>> https://www.dropbox.com/s/w7dmmcbocnmjfbo/gcs-stats-testnet.csv?dl=0
>>
>>
>> We look forward to getting feedback from all of y'all!
>>
>> -- Laolu
>>
>>
>> [1]: https://github.com/lightninglabs/neutrino
>> [2]: https://github.com/Roasbeef/btcd/tree/segwit-cbf
>> [3]: https://github.com/Roasbeef/btcutil/tree/gcs/gcs
>> [4]: https://github.com/lightningnetwork/lnd/
>>
>> -- Laolu
>>
>>
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next prev parent reply other threads:[~2017-06-09 3:59 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-01 19:01 Olaoluwa Osuntokun
2017-06-01 21:00 ` Eric Lombrozo
2017-06-01 21:33 ` Matt Corallo
2017-06-01 22:10 ` Olaoluwa Osuntokun
2017-06-02 2:15 ` Chris
2017-06-02 2:28 ` Gregory Maxwell
2017-06-02 3:35 ` Alex Akselrod
2017-06-02 16:07 ` Chris Pacia
2017-06-02 4:49 ` Olaoluwa Osuntokun
2017-06-09 3:59 ` Olaoluwa Osuntokun [this message]
2017-11-09 23:44 ` Olaoluwa Osuntokun
2017-06-02 6:00 ` Karl Johan Alm
[not found] ` <CAE0pnx+RRAP269VeWAcxKbrcS9qX4LS8_6nY_js8X5NtQ22t_A@mail.gmail.com>
[not found] ` <CAE0pnxLKYnwHnktTqW949s1AA9uK=6WnVYWmRoau8B1SszzYEg@mail.gmail.com>
[not found] ` <CAE0pnxJxHYQ4+2pt3tt=1WZ0-K0vDxGB4KBXY+R=WfktMmATwA@mail.gmail.com>
2017-06-02 17:55 ` Alex Akselrod
2017-06-05 2:06 ` Karl Johan Alm
2017-06-09 3:03 ` Olaoluwa Osuntokun
2017-06-07 21:41 ` Gregory Maxwell
2017-06-09 3:42 ` Olaoluwa Osuntokun
2017-06-09 4:47 ` Olaoluwa Osuntokun
2017-06-08 9:50 ` Tomas
2017-06-09 3:50 ` Olaoluwa Osuntokun
2017-06-09 8:26 ` Tomas
2017-06-19 11:58 ` Andreas Schildbach
2017-06-19 12:26 ` bfd
2017-06-19 15:15 ` Tom Zander
2017-06-19 15:49 ` Jonas Schnelli
2017-06-19 15:59 ` Andreas Schildbach
2017-06-19 16:22 ` Jonas Schnelli
2017-06-19 16:36 ` adiabat
2017-06-19 20:49 ` Andreas Schildbach
2017-06-20 7:03 ` Eric Voskuil
2017-06-19 16:07 ` Tom Zander
2017-06-19 16:30 ` Jonas Schnelli
2017-06-19 16:38 ` Tom Zander
2017-06-19 15:43 ` Andreas Schildbach
2017-06-19 16:10 ` Jonas Schnelli
2017-06-19 22:41 ` Gregory Maxwell
2017-06-20 9:52 ` Tom Zander
2017-06-20 13:08 ` bfd
2017-06-20 17:20 ` Adam Back
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