Topic: Scalability (Read 26015 times)

This has probably been discussed allready but it seem to me that the scalability and performance problems may be relatively easy to solve.

Consider a peer to peer file sharing app. A file is split into a collection of blocks. Each peer downloads the blocks they need in order of priority. Even if none of the peers have all the blocks (original source has gone offline) it is still possible for the peers to piece together their collective copy. I suppose the point is that no one bitcoin node needs to have all the blocks and transactions at any one time for the collective to hold a secure and trused copy between them. So a bitcoin client could have a set limit on the amount of resources that it will use, based on the hardware availiable and the users preference. An indiviual user can hold the information of highest priority to themself and use the remaining resources for other randomly chosen blocks. I suppose this is where transaction fees come in, encouraging users to commit more resources by rewarding them financialy for processing certain transactions of high priority.

I hope that made some sense. I think that is how it is supposed to work, but that comes from reading beteen the lines, so I may be way off.

Is it possible to generate blocks if a lightweight generator  ask many nodes for hash of previous blockchain and transactions in current block?

Well, I don't see problems with trust if properly implemented.

The whole idea that downloading zipped blocks is faster than downloading "from network" means performance problems in BitCoin client.

I know that long time ago bitcoin client utilized very little of available bandwidth because of cache flushing after each single block or something like that. But Satoshi fixed that. Did someone test how much bandwidth (of available bandwidth) is used and how much data is downloaded when a new chain is downloaded?

If bandwidth is underutilized - then networking code must be rewritten. If zipping helps to compress chain (I'm not sure because chain contains a lot of hashes and those are random and thus incompressible) - then compression must be built in.  If chain is downloaded many times - then trust scheme must be changed to Emule AICH or similar:
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Newer versions of eMule support AICH - Advanced Intelligent Corruption Handling. It is meant to make eMule's corruption handling competitive with BitTorrent. SHA-1 hashes are computed for each 180kb sub-chunk and a whole SHA-1 hash tree is formed. AICH is processed purely with peer-to-peer source exchanges. eMule requires 10 agreeing peers regarding the SHA-1 hash, so rare files generally do not benefit from AICH.
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So instead of asking each peer for blocks, Bitcoin client can ask for block hashes and even for hashes of block ranges (to save hash traffic) to download each block only once.

Also, transaction clearinghouse function can be easily be built in the current network. We can have a "trust network to validate transactions" setting.

Also, blockchain is not needed to generate blocks, so a purely generating node can ask other nodes for hashes needed to build its block instead of asking for chain. And people will be able to contribute either bandwidth or CPU or both. Now they are forced to contribute bandwidth.

I am for example in a remote village in Nigeria connecting over EDGE. 30 MB of chain costs me 9 NGN that is 0.06 USD. But with terabytes of traffic that will not be affordable. Even now 30 MB is not affordable because a lot of people earn less than $200 a month and 0.06 USD is the cheapest possible wholesale price because I pay $80 a month for a 3 GB cap at 120 kbps down / 80 up I measured.

Debit/credit cards industry is not developed here, but everyone has a cheap fake Chinese phone with J2ME and thus capable to run some client software.

Has there been any progress or further discussion on establishing better scalability for future of Bitcoin?

When these "client" or "lightwight client" will be released? Or something like sample code?
It would be interesting to implement it on, say, java smartcard environment.

I suppose this might be a good reason to make www.mybitcoin.com or an equivalent your primary bitcoin account/wallet. All you need for it is a browser.

If you are a merchant, you will be your own server, no? Now if your own server gets hacked somehow with a dummy placed in between, this could be a problem...

If you are a merchant and the server tells you that your transaction with a certain client is valid when in fact it is not, then the goods or services you provide, you provided for free. Now suppose this person buys a Ferrari... You're screwed. And that's, in fact, one of the well known types of attacks: an attack on trust. You will of course find another service provider, but the damage will already be done.

I'm in agreement on your points. However you have to admit that what you wrote at the end sounded funny!

Gee, why would an anonymous server lie about my money?  :-)

In reality you are correct. There are very few things to lie about. I could think of a few things though.

What's funny?

A server lying about whether or not your transactions are valid would be like your ISP lying about whether or not your HTTP requests are valid or not.

If they lie, you'll very quickly find another service provider (or download a Bitcoin iPhone app that doesn't suck and say that your transactions are invalid).

lMAO!!!

Could you, or anyone else, speculate about the numbers of transaction per second limit for the current system?

What could be the maximum transaction throughput (in the number of transactions, not in the volume)? What could it depend on?

What is the future limits on that number, in the case the system will grow?

Just consider Bitcoin as a system for micro- or even nano-payments?
Like paying 0.000001 (or less) for posting in a forum? Or paying even less for just reading the forum (with advertising stripped)?
That would generate far more than a million transactions per day.
That would create unprecedented transaction flow.
Will it hurt the other participants, which are not nano-payers?

We could test the "system" speed if we start sending small amounts in a circle between wallets and thus flooding the system.
Or we couldn't?
If we do that, what effect will it cause?

Would you mind against such an experiment? If you veto that, then how could you stop it?

It's good the spec already addresses this problem. I'd like to see some more in depth access to things like the coin list (so we can choose to spend coins based upon who sent them to us, etc) and the client list. For example, all of my computers at home -connect to my router, which runs (but does not generate) with port 8333 open.

I wish there were some way to prioritize network traffic to my own local nodes over remote nodes.

The design outlines a lightweight client that does not need the full block chain.  In the design PDF it's called Simplified Payment Verification.  The lightweight client can send and receive transactions, it just can't generate blocks.  It does not need to trust a node to verify payments, it can still verify them itself.

The lightweight client is not implemented yet, but the plan is to implement it when it's needed.  For now, everyone just runs a full network node.

I anticipate there will never be more than 100K nodes, probably less.  It will reach an equilibrium where it's not worth it for more nodes to join in.  The rest will be lightweight clients, which could be millions.

At equilibrium size, many nodes will be server farms with one or two network nodes that feed the rest of the farm over a LAN.

I second the DHT idea for maintaining a client list - we can't have millions of people relying upon an IRC channel, etc.  As far as the scaling issue goes, the issue is not at all HDD space, its network bandwidth.  Everyone is forgetting, its not bytes_per_transaction*transactions, which is the number everyone is using.  That number, as everyone has said, is fully manageable.  No, the number we're interested in is bytes_per_transaction * transactions * number_of_clients * total_hops_beyond_first_between_all_clients_combined

THIS is the amount of bandwidth which the protocol for BTC consumes as the network scales.  We're not just talking about sending one copy of each transaction to each client - we're talking about multiple clients broadcasting potentially redundant data to one another, and doing it across numerous hops, meaning numerous rebroadcasts.  Much larger number, much more difficult to handle.  However, it is manageable, just not in the current incarnation of network handling in the client.

Perhaps in the "popular" phase, BTC chains could be broken up by region, similar to the purviews of domain name authorities now - and there could be an alternative protocol for transactions across these regional boundaries?  This would help the raw numbers of the problem, and also cut down on latency and related issues.  Not that I think this is an excellent solution - but P2P flooding across all active clients is obviously out barring some massive breakthrough in quantum computing or whatnot.

you don't even have to imagine , actually it's already possible to "remote-control" the node, so just create ur own little lightweight-client, that just sends and gets some info to/from your (highspeed-connected, hdd-packed) homeserver.

some kind of "managed server-client-version" already exists in MyBitcoin, you could run something like that on your own webhost and connect to it from wherever u are on whatever connection-speed.

the "lightweight client" doesnt have to be one, but connect to it and tell it what todo.
we can do that with JSON.

Um. Sure. I think I've gone full circle. I think Gavin said it best:

In this scenario, the Bitcoin client could remain largely the same as it is today, although the focus would be that it is used on the "super-nodes" or "transaction servers" or "proxy servers" (these systems would probably serve all three roles) or by anyone wishing to play in that game. If the Bitcoin client was augmented to use DHT then that may be improvement but there is still a need for a "lightweight client" as Gavin described above. It seem's Gavin's "lightweight client" concept obviates my scalability concerns somewhat.

I've had luck with testing of packaging blocks into a zip file and dumping them on a new Bit Coin to speed up the block download process. I'll leave the link in my signature and if anyone finds it useful or time saving, feel free to donate. 

Not really. If you're worried, you can always run your very own server.


Nothing. Unless you happen to use one of those supernodes, which you don't have to, because you can run your own supernode. Or use a trusted one, much like people trust Google with their E-Mail.


It isn't easier to implement? I'd like to see some proof here.

Counterexample: The totally distributed E-Mail system developed at Rice University is a hell of a lot more complex than running a (network of) semi-centralized mail server(s).


Um. That's exactly what a supernode server would do.

I agree, I've been looking into packaging "blocks" for download so that you can install the client, unzip a fresh stack of blocks and let the client finish off the rest to get people up and running faster. I'm experimenting with Windows and Linux clients (don't have a Mac that can run the Mac client, sorry folks)

Hopefully that will help with the issue.

Of course, the trust factor comes in (should I download these from this guy instead of letting the network do it for me)