Questions tagged [distributed-systems]

Questions about the challenges of solving problems with multiple cooperating but separate agents.

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Using vector clocks vs. directed acyclic graph for causality detection in distributed systems

I'm trying to understand how vector clocks compare to DAGs for causality detection in a distributed system. When trying to detect causality relations in a distributed system, a very commonly proposed ...
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Is there any guarantee in asynchronous systems?

We know that in an asynchronous system, no assumptions about process execution speeds or message delivery times are made. My question is: can we present any guarantee in asynchronous systems? Some ...
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Averaging a list of variances

In a setting where I have n clients each owns a subset of the dataset, each computes the mean and variance on his data and send them to the server. The server would average all means and variances. ...
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1answer
20 views

How does random number probabilities work in distributed systems?

Let's say I have a code which does coin toss at 25% win probability. If I run this code n number of times in the same system it will yield ~25% win. If I run this code on n devices (once each) will ...
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What is the relation between a web server and a local file serve in distributed systems?

I am learning distributed systems ( although I am an Electrical engineer ) using the book distributed systems concepts and design. The author says that "A web server is often a client of a local ...
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How does Lamport imply anomalous behavior is impossible given these constraints?

Lamport's paper: Time, Clocks, and the ordering of Events in a Distributed System Anomalous behavior occurs because Lamport's logical clocks are not enough to guarantee that the total ordering of ...
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Why does the converse of the clock condition imply that any two concurrent events occur at the same time?

In Lamport's paper, Time, Clocks, and the ordering of Events in a Distributed System he says that the converse of the clock condition does not hold and if it did, we could expect concurrent events to ...
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MMOGs as an example of distributed systems

In the book "Operating System Concepts and Principles" , the authors mentions massively multiplayer online games as an example of Distributed Systems. They mention that as an example of ...
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Synchronization in Distributed Systems

If there is no global clock in Distributed systems , then what is the solution for synchronization in DS ? Also , no global clock in DS is a direct consequence of the fact that the only communication ...
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Method of communication in Distributed Systems

Why the method of communication used in DS is message passing and not shared memory ?
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What is a distributed algorithm for generating random “private” pair-matchings?

Say you have 2N named peers (agents) able to address each other by their name and communicate freely among them. What distributed algorithm could they use in order to randomly pair up? The final ...
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Distributed Serializable Snapshot Isolation

I was wondering if there is any research on distributed transaction algorithms for Serializable Snapshot Isolation. I found Binnig, C. et al.: Distributed snapshot isolation: global transactions pay ...
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Why is shared register's consensus number 1?

I'm trying to understand the consensus number concept. It is trivially clear that a shared register doesn't create any problem when there is only one thread using it. By why does its consensus number ...
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1answer
25 views

Leader Election: Every bit-reversal ring is $\frac{1}{2}$-symmetric

I have a proof that I need help with. Like the title says, the theorem is that every bit-reversal ring is $\frac{1}{2}$-symmetric. The theorem is for Leader Election algorithm in synchronous ring. The ...
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Why is the 'Integrity' property required in consensus protocols?

Formally a consensus protocol must satisfy the following three properties: Termination Eventually, every correct process decides some value. Integrity If all the correct processes proposed the same ...
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Randomly assign n elements to n agents such that each agent only knows its own element

Problem I'm working on an app that involves shuffling and distributing playing cards to players. As a challenge, I tried to solve this problem in a way that doesn't require a trusted intermediary. In ...
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81 views

Distributed predicate computation on event stream

My question is actually a request for papers, articles, texts or books on the problem that I'm trying to solve on my work. I'm working on a program that computes a predicate value (true or false) for ...
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Why chord protocol (peer - to - peer) maintains a finger table instead of entire membership list (using SWIM)?

Chord uses finger table for querying and it takes O(log(N)) to get the result. But why not maintain the entire membership list and get result in O(1) ?
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Number of referee nodes required in distributed leader election algorithm

I know the reason as to why $O(\sqrt{n\log n})$ referee nodes are required. What I don't understand is how to arrive at that value, when I have $7\log n$ candidate nodes. Please forgive me if this is ...
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1answer
23 views

Confused between 2 phase locking and 2 phase commit

I understand that both algorithms are very different, but what I don't understand is whether they achieve the same thing in the end. 2PC is for atomic commits and 2PL is for serializable isolation. ...
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What are some advanced background topics I'll need for distributed systems and networks research?

I am a new graduate student in Computer Science who would like to be able to read and understand modern and new distributed systems research papers. My current background / courses and understanding ...
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What is the current definition for HPC systems - do they include both GPUs and MIMD Supercomputers?

I have seen several definitions across the internet and this question still bugs me.
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Finding the timestamps of processes implementing Lamport's clocks

I have been asked this question, but don't know how to go about answering it. Three process, which are implementing Lamport's clocks, are running and a lot of events are taking, place including some ...
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Count nodes with more than 3 neighbours in distributed computing, initiating by one site

I have an algorithm that visit all the nodes on a graph in distributed computing , the initiator is one site only , I want to change it so that the initiator can in the end of the execution know the ...
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What are the advantages of NHSX centralised protocol for Contact Tracing?

Apple and Google have published a protocol for privacy-presercing contact tracing - https://www.apple.com/covid19/contacttracing/ They use a decentralised approach where the 'matching' process take ...
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A single Paxos instance deciding on different values

I have recently been taught about the Paxos consensus protocol in my university's distributed systems course. There is a particular case that I find troubling: Suppose there are two proposers P1 and ...
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Request committed by only some non-faulty nodes in PBFT

I have recently learned about the protocol described in the paper titled "Practical Byzantine Fault Tolerance", as part of my university course on distributed systems. There was one example ...
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58 views

Why is two-phase commit better than naive master-slave replication?

In the context of a distributed database, I'm trying to understand why 2PC (as described in e.g. https://www.cs.princeton.edu/courses/archive/fall16/cos418/docs/L6-2pc.pdf) is better than the ...
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25 views

Optimize Max-flood algorithms bounds

In distributed algorithms, The Max Flood algorithms finds the leader in a network of processes In O(diam) time and with |E|*diam ...
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Why is a threshold determined for Byzantine Fault Tolerance of an “Asynchronous” network? (where it cannot tolerate even one faulty node)

In following answer (LINK: https://bitcoin.stackexchange.com/a/58908/41513), it has been shown that for Asynchronous Byzantine Agreement: "we cannot tolerate 1/3 or more of the nodes being ...
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45 views

Doesn't Linearizability implies Serializability?

Serializability is a concurrency scheme where the concurrent transaction is equivalent to one that executes the transactions serially. In Linearizability, Once write completes, all later reads should ...
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Arbitrary fault abstraction in 'Reliable and Secure Distributed Programming'

In the book by Cachin, Guerraoui, Rodrigues they discuss an arbitrary fault abstraction. It seems to me that this abstraction does not include crashes in its behavior. I think this because they ...
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Environmental/Economical benefits of not transmitting parts of a video?

Are there any potential environmental och economical benefits (in terms of infrastructure) derived from not transmitting video packets unless absolutely necessary or requested by the client for Media-...
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What are the correlation between Actor model and Reactive Programming

Could anyone explain the difference/relation between the Actor model and Reactive programming? It seems that they are located at different levels of abstraction - one can design the interaction ...
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1answer
119 views

Why aren’t distributed computing and/or GPU considered non-deterministic Turing machines if they can run multiple jobs at once?

So we know a nondeterministic Turing machine (NTM) is just a theoretical model of computation. They are used in thought experiments to examine the abilities and limitations of computers. Commonly used ...
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What distributed consensus algorithms don't rely on a time source?

I'm looking for information about distributed consensus algorithms that: maintain a consistent transaction log across all healthy nodes have similar high-availability properties to Paxos (i.e. not ...
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25 views

Consensus without majority

I am new to distributed computing but after a quick look at Paxos and Raft it is clear that for those algorithms to work majority of the servers should be up and running. So is it fundamental to ...
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219 views

What is the difference between masking and tolerating failures?

Distributed Systems 5ed by Coulouris says on p21-22 1.5.5 Failure handling Detecting failures: Some failures can be detected. For example, checksums can be used to detect corrupted data in a ...
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143 views

Do arbitrary/Byzantine failures include omission failures and timing failures?

Distributed Systems 5ed by Coulouris says on p68 2.4.2 Failure Models Omission Failures ... Arbitrary Failures The term arbitrary or Byzantine failure is used to describe the worst ...
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1answer
37 views

How to convert a centralized algorithm to a distributed algorithm?

Is there any algorithm or procedure to convert a centralized algorithm to a distributed algorithm? Is there any theoretical result or relevant complexity analysis?
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18 views

Ideal time complexity in analysis of distributed protocol

I need some explanation about the definition of ideal time complexity. My textbook says: The ideal execution delay or ideal time complexity, T: the execution delay experienced under the ...
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1answer
48 views

How do I use message passing to find the maximum of all values in a grid?

I am working on a problem. I have been tracing much more simple problems by hand, but I got this one and I am truly at a loss. I do not know how to research this to help me figure it out. I am truly ...
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53 views

Leader election in synchronous ring with unreliable communication channels

As a part of my Distributed Systems course I am required to provide an algorithm that is able to elect a leader in a synchronous bidirectional ring, where every message that is sent may be lost (lets ...
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1answer
27 views

Implementing reliable pairwise average in distributed systems

Consider an asynchronous and unreliable distributed system. Each node has a value. Suppose that p and q are two neighbor nodes of the system (p_val and q_val are the values of p and q respectively). p ...
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18 views

How to divide services and capacities in a graph?

Given a graph where some nodes can provide some services with x,y,z... capacities. A node connected to multiple nodes needs to divide these services to the connected nodes and these nodes themselves ...
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Byzantine Generals Problem - Regular Set of Neighbors

Going through Lamport's paper, I'm a little confused by the second part of the regular set of neighbors definition. A set of nodes $\{i_1, \ldots, i_p\}$ is said to be a regular set of neighbors ...
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Byzantine Generals Problem - Oral and Signed Messages

Having just read through Lamport's paper, I was hoping someone could clarify a few things on the Oral and Signed message algorithms. Why do we have to run $OM()$, recursively by $m$? If a majority of ...
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1answer
26 views

Guaranteed existence of a blocking set in the accept definition of Stellar

In the SCP, condition 2 of the accept definition allows a node to vote for one statement and later accept a contradictory one. Condition 2 assumes the existence of a v-blocking set which has not only ...
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Paxos algorithm, accept phase

From the wiki https://en.wikipedia.org/wiki/Paxos_(computer_science) If a Proposer receives enough Promises from a Quorum of Acceptors, it needs to set a value v to its proposal. If any Acceptors had ...
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Given two or more nodes in a network, is it possible to determine the one-way link latencies between two nodes that share a bi-directional connection?

We already know that detecting the one-way latency between only two nodes is impossible. However, if I have a number of nodes in the same subnet that all know about each other, can measure round-trip ...

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