Questions tagged [scp]

For questions regarding the Stellar Consensus Protocol (SCP).

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How can a node safely apply its externalized state while still allowing late commit messages?

Consider a case with Qset { N: 6, Threshold: 4}, 6 nodes and a threshold of 4. If a Node has received 4 commit confirmed messages for a ballot b then it is safe to act on it - as an example by ...
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What happens in the unlikely case that a Validator has no transactions to nominate but it's time to start a nominating round?

In the case that a Validator's transaction pool is empty, is the following code ever called inside of HerderImpl::triggerNextLedger?: mHerderSCPDriver.nominate(slotIndex, newProposedValue, proposedSet,...
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30 views

What is the difference between SCP and FBA?

The Stellar white paper "presents federated Byzantine agreement (FBA), a model suitable for worldwide consensus." It then goes on to state that it "further presents the Stellar ...
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15 views

How does a node vote “against” a proposal?

In the SCP white-paper it's mentioned that when a node votes on a proposal, it promises that it has never voted against that proposal. However, how exactly would a node vote "against" a ...
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43 views

Error merging bucket, and FATAL SCP crash

I have a private network based on Stellar core v.10 with 3 nodes and 66% 2/3 consensus, after 6 month successfully worked this network crash with message: insufficient buffer space in xdr_generic_get....
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The Balloting protocol of SCP - Step 9

The Paper on SCP at https://pdfs.semanticscholar.org/3bab/b89369eed603ce3c702f447ee6274429cda1.pdf?_ga=2.113216397.862297418.1585318681-2089854760.1525259881, describe the concrete balloting protocol ...
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14 views

Why is there a potential for a quorum split in this example quorum configuration?

The QuorumIntersectionChecker has a getPotentialSplit function. It doesn't seem to be documented. I've tried to use it while experimenting with various quorum configuration. Here is one such ...
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39 views

What state is a transaction in after being succesfully posted?

Related to how to trace the state of a transaction after submit? After a transaction has been sent to the Post Transaction endpoint and it returns a successful response: A successful response (i.e....
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127 views

Stuck in “Joining SCP” state with info “Lost track of consensus”

I just trying to build a private network with two nodes(two different physical hosts) and all of two nodes are validator nodes, but I just stuck in the "Joining SCP" state when I run stellar-core run -...
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Unable to find 5 sec slot timing in code base

I was trying to understand the stellar code base and was looking for a place where 5 sec slot timing is hardcoded (if I am not wrong). But unable to find that, instead in ovalayManagerImpl.cpp file I ...
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21 views

SCP Safety Guarantee Question

I have a question regarding the Stellar Consensus Protocol. In the SCP whitepaper it is stated on page 14 under the point 5.4 "Accepting is not enough": "But as discussed in Section 4.1, the only ...
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78 views

Peer getting rejected from the private network

Hi I created a private network of 3 nodes with the following configurations like this: # more than one node should validate. threashold = 2 [QUORUM_SET] THRESHOLD_PERCENT=34 VALIDATORS=["$node01","$...
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47 views

Problem in connecting new node to the network

I am trying to setup a network of 2 nodes(node01, node02) and then want another node to be connected to that network. Here is what my configuation is : For node 1: [QUORUM_SET] THRESHOLD_PERCENT=...
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pBFT in closed 100 node setup

Can Practical Byzantine Fault Tolerance (pBFT) be considered as one of the quorum configurations of SCP of stellar? I am considering the situation where the 100 nodes are run in a closed network.
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51 views

New node is lagging behind the old one

Hi I was doing some experiment (especially after the news of stellar network going down) in my simple 2 nodes private network and got some confusion. Here are the steps I follow: Configured network ...
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42 views

Nomination protocol differences between implementation and specification

To get a more intuitive understanding of the SCP I'm trying to implement a generic version of it. For the implementation I'm using 3 references: Stellar-core source code The SCP paper Internet Draft ...
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131 views

Partial vs Complete Catchup: what are the differences in terms of security?

Lets assume I power-up a new core and join (as validator) to a network of pre-existing other nodes. In addition, to speed things up, I chose to do a partial catchup from one history archive. Now, ...
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20 views

Partial Catch-up on Validator nodes

I'm curious to know what would happen in the following scenario: Suppose I have a network of 7 validator cores of which 4 performed a complete catchup (replay) of history (say a month's worth of ...
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42 views

How does a stellar node know that node its communicating with is definitively in or outside its quorum group?

In order for SCP to function properly, a given node has to know that a quorum related message originated from a node in its quorum set. How does this node know for a fact that the message originated ...
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103 views

How should one decide how many and which nodes to select in the quorum set when configuring a Stellar Core Node

How should one decide how many and which nodes to select in the quorum set when configuring a Stellar Core Node (in archiver mode)? There is a list of validators in the link below, should all or some ...
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234 views

What are the good configurations for having a running cluster of 3 nodes?

I am trying to set up a private stellar cluster with at least 3 nodes. I am able to setup a 2-nodes cluster but when it comes to add another node, the cluster is broken and only one node is synced. ...
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88 views

Can a transaction be successful in a 2-node private Stellar Network?

I have a 2-node private network running, when I try to submit a transaction using an XDR generated from the Stellar Lab, it first shows up as "PENDING", then one of the node stops working. Any idea, ...
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What are the message size limitations of stellar consensus protocol?

The question is a two part question: What is the message size limitation of stellar consensus protocol? Also how does the message size affect the TPS of stellar?
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54 views

Could consensus period be changed?

I'm trying to run a private network and so modifying stellar-core's source code is not out of the question. I noticed that the network is right now configured to come to consensus every 5 seconds, ...
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89 views

How does the Stellar protocol ensure a network doesn't have disjoint quorums?

Does Stellar maintain a set of nodes to achieve quorum intersection? If not, how can a Stellar network achieve quorum intersection at all times, meaning no disjoint quorums at all in the network?
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How a new node trusts another node in the network

Let's assume that a new node joined in the network.As per the SCP how this new node trusts another node in the network? Does this happens by exchanging messages between other nodes in the network ? ...
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SCP. Does non-intersecting quorums have different ledgers?

As I understand "slot" = ledger number, "value" = set of transaction. So сould you explain what happens when I(simple node with quorum slice) create a transaction ? 1) Do all nodes in stellar-...
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138 views

How does a node discover the quorums that it is in?

In order for a node to determine that a ledger has been confirmed, it needs to know that a proportion of other nodes in one of its quorum has accepted the ledger. In order to determine which nodes ...
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2answers
47 views

(SCP) When does a node get its higher-layer software's input?

According to the SCP document (draft-mazieres-dinrg-scp-04, https://datatracker.ietf.org/doc/draft-mazieres-dinrg-scp/), the following paragraph describes how a node get its higher-layer software's ...
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140 views

Is there a minimal implementation of Stellar Consensus Protocol besides stellar-core?

I'm learning about consensus and I'd like to explore SCP in depth. However, the stellar-core implementation is difficult for a newcomer to grok. Is there a minimal SCP implementation elsewhere I can ...
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162 views

Why does the high level threshold level for quorum have to be above 66%?

What is reason that the threshold of consensus bearing nodes must be above 66% for the network to operate successfully? This is straight from the docs of the stellar-core_example.cfg file. ...
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297 views

What is asymptotic security and why does Stellar, but not POW exhibit this?

One of the benefits mentioned of SCP in comparison to POW is 'asymptotic security' https://www.stellar.org/blog/stellar-consensus-protocol-proof-code/. What does this form of security mean in practice ...
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Questions about SCP and federated voting steps, with a focus on the Internet-Draft

I recently have studied the Stellar Consensus Protocol (SCP) based on the internet draft here: https://datatracker.ietf.org/doc/draft-mazieres-dinrg-scp/. I have several questions as follows. In the ...
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258 views

What does it mean with “surge pricing in effect” at Stellar-Core?

As I tested my private network by flooding transaction (around 60TPS) via Horizon using JS-sdk, SCP errored. The only abnormalty that I observed was: [Herder WARNING] surge pricing in effect! 142 ...
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197 views

How can I query or visualize the quorum slices of the Stellar network?

I think I remember faintly that a while ago there was a JS-based visualization of the quorums between various validators on Stellar but I seem unable to find it again. As far as I understand the ...
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109 views

Consensus about a transaction set

In the description of the transaction life cycle it is mentioned that: SCP resolves the differences between the various transaction sets proposed and decides on the one transaction set that the ...
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How are timestamps deemed invalid?

The Stellar Consensus Protocol orders block candidates (via ballots) by the maximum timestamp and union of their transactions. It says that "values [transactions/ballots] with invalid timestamps will ...
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155 views

How is the node ID assigned to a stellar core node?

Running the quorum command on a stellar-core node will presumably show the current node ID. The node ID looks like a stellar public account key. How is this assigned? Is the similarity to a public ...
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194 views

When is a slot created in the Stellar Consensus Protocol?

At what time during the protocol is a unique slot created for the nodes to vote on?
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113 views

How can a validator node earn trust on the network?

It's my understanding the SCP achieves consensus by having validator nodes agree with other validator nodes that they trust. Anyone can become a validator node, but won't they not actually be ...
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908 views

How does the Stellar Consensus Protocol prevent Sybil attacks?

A Sybil attack is an attack where a single adversary controls multiple nodes on a network in order to influence voting to their advantage. It is unknown to the rest of the network that the nodes are ...
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672 views

Are there any known weaknesses in the Stellar Consensus Protocol?

Are there any known situations, although infrequent or difficult to meet, where the Stellar Consensus protocol could not work well or where the network can be attacked by malicious nodes?