Research | ProbeLab Analytics

CoNEXT-SW '21 Workshop Paper · Dec 2021

Leveraging Node Heterogeneity to Improve Content Discovery and Content Retrieval in Peer-to-Peer Networks

Dennis Trautwein · Moritz Schubotz · Bela Gipp

Distributed content-addressed networks like the Interplanetary File System (IPFS) have gained popularity in recent years. It is used as a data storage layer for Blockchain applications or generally as a censorship-resistant file-sharing network. In the past, many traditional peer-to-peer networks eventually implemented super-peer sub-topologies within their otherwise nonhierarchical network to increase the efficiency of various system tasks. While it can be observed that IPFS also holds such tendencies, no formalism supports these developments. This article will present a research project that will investigate if and how a super-peer architecture can complement the IPFS network from a content discovery and retrieval perspective. Further, first preliminary results on peer churn rate in the IPFS and Filecoin networks will be discussed.

TON '21 Journal Article · Nov 2021

A Congestion Control Framework Based on In-Network Resource Pooling

Sergi Rene · Onur Ascigil · Yiannis Psaras · George Pavlou

Congestion control has traditionally relied on monitoring packet-level performance (e.g., latency, loss) through feedback signals propagating end-to-end together with various queue management practices (e.g., carefully setting various parameters, such as router buffer thresholds) in order to regulate traffic flow. Due to its end-to-end nature, this approach is known to transfer data according to the path’s slowest link, requiring several RTTs to transmit even a few tens of KB during slow start. In this paper, we take a radically different approach to control congestion, which obviates end-to-end performance monitoring and careful setting of network parameters. The resulting In-Network Resource Pooling Protocol (INRPP) extends the resource pooling principle to exploit in-network resources such as router storage and unused bandwidth along alternative sub-paths. In INRPP, content caches or large (possibly bloated) router buffers are used as a place of temporary custody for incoming data packets in a store and forward manner. Data senders push data in the network and when it hits the bottleneck link, in-network caches at every hop store data in excess of the link capacity; nodes progressively move/send data (from one cache to the next) towards the destination. At the same time alternative sub-paths are exploited to move data faster towards the destination. We demonstrate through extensive simulations that INRPP is TCP friendly, and improves flow completion time and fairness by as much as 50% compared to RCP, MPTCP and TCP, under realistic network conditions.

AFT '21 Conference Paper · Nov 2021

Shard Scheduler: Object Placement and Migration in Sharded Account-Based Blockchains

Michał Król · Onur Ascigil · Sergi Rene · Alberto Sonnino · Mustafa Al-Bassam · Etienne Rivière

We propose Shard Scheduler, a system for object placement and migration in account-based sharded blockchains. Our system calculates optimal placement and decides on object migrations across shards. It supports complex multi-account transactions caused by smart contracts. Placement and migration decisions made by Shard Scheduler are fully deterministic, verifiable, and can be made part of the consensus protocol. Shard Scheduler reduces the number of costly cross-shard transactions, ensures balanced load distribution and maximizes the number of processed transactions for the blockchain as a whole. To this end, it leverages a novel incentive model motivating miners to maximize the global throughput of the entire blockchain rather than the throughput of a specific shard. In our simulations, Shard Scheduler can reduce the number of costly cross-shard transactions by half while ensuring equal load and increasing throughput more than 2 fold when using 60 shards. We also implement and evaluate Shard Scheduler on Chainspace, more than doubling its throughput and reducing user-perceived latency by 70% when using 10 shards.

BCCA '21 Conference Paper · Nov 2021

Discovering the Ethereum2 P2P Network

Mikel Cortes-Goicoechea · Leonardo Bautista-Gomez

Achieving the equilibrium between scalability, sustainability, and security while keeping decentralization has prevailed as the target solution for decentralized blockchain applications over the last years. Several approaches have been proposed by multiple blockchain teams to achieve it, Ethereum being among them. Ethereum is on the path of a major protocol improvement called Ethereum 2.0 (Eth2), implementing Sharding and introducing the Proof-of-Stake (PoS). As the change of consensus mechanism is a delicate matter, this improvement will be achieved through different phases, the first of which is the implementation of the Beacon Chain. As Ethereum1, Eth2 relies on a decentralized peer-to-peer (p2p) network for the message distribution. Up to date, we estimate that there are around 5.000 nodes in the Eth2 main net geographically distributed. However, the topology of this one still prevails unknown. In this paper, we present the results obtained from the analysis we performed on the Eth2 p2p network. Describing the topology of the network, as possible hazards that this one implies.

BRAINS '21 Conference Paper · Sep 2021

Resource Analysis of Ethereum 2.0 Clients

Mikel Cortes · Luca Franceschini · Leonardo Bautista-Gomez

Scalability is a common issue among the most used permissionless blockchains, and several approaches have been proposed to solve this issue. Tackling scalability while preserving the security and decentralization of the network is an important challenge. To deliver effective scaling solutions, Ethereum is on the path of a major protocol improvement called Ethereum 2.0 (Eth2), which implements sharding. As the change of consensus mechanism is an extremely delicate matter, this improvement will be achieved through different phases, the first of which is the implementation of the Beacon Chain. For this, a specification has been developed, and multiple groups have implemented clients to run the new protocol. This work analyzes the resource usage behavior of different clients running as Eth2 nodes, comparing their performance and analyzing differences. Our results show multiple important network perturbations and how different clients react to them. We discuss the differences between Eth2 clients and their limitations.

ICBC '21 Conference Paper · Jun 2021

FLOCK: Fast, Lightweight, and Scalable Allocation for Decentralized Services on Blockchain

Navin V. Keizer · Onur Ascigil · Yiannis Psaras · George Pavlou

Many decentralized services have recently emerged on top of blockchain, offering benefits like privacy, and allowing any node in the network to share its resources. In order to be a competitive alternative to their central counterparts, their performance needs to match up. Specifically, service allocation remains a performance bottleneck for many decentralized services.In this paper we present FLOCK, an allocation system which is highly scalable, fast, and lightweight. Furthermore, it allows nodes to indicate their preference for clients/sellers without needing to submit bids by using stable matching algorithms. We decouple the price discovery and outsource this function to a smart contract on the blockchain.Additionally, another smart contract is used to orchestrate the allocation and take care of service discovery, while trusted execution environments securely compute allocation solutions, and off-chain payment networks are used to send rewards.Evaluation of FLOCK shows that gas costs are manageable and improve upon other solutions which leverage auctions, and that our instance of the stable matching algorithm greatly improves run-time and throughput over auction counterparts. Finally, our discussion outlines practical improvements to further increase performance.

IFIP '21 Conference Paper · Jun 2021

IPFS-FAN: A Function-Addressable Computation Network

Alfonso de la Rocha · Yiannis Psaras · David Dias

Permissionless computation is one of the missing pieces in the web3 stack in order to have all the tools needed to “decentralise Internet services”. There are already proposals to embed computation in decentralised networks like smart contracts, or blockchain networks for computational offloading. Although technically sound, their computational model is too restrictive to be used for general purpose computation. In this paper, we propose a general architecture of a decentralised network for general-purpose and permissionless computation based on content-addressing. We present a proof-of-concept prototype and describe in detail its building blocks.

IFIP '21 Conference Paper · Jun 2021

The Case for AI Based Web3 Reputation Systems

Navin V. Keizer · Fan Yang · Yiannis Psaras · George Pavlou

Initiatives such as blockchains and decentralized storage networks are pushing for a decentralized Web3 to replace the current architecture. At the core of Web3 are network resource sharing services, which allow anyone to sell spare network capacity in return for rewards. These services require a way to establish trust, as parties are potentially malicious. This can be achieved by reputation systems. In this paper we make the case for using deep reinforcement learning in Web3 reputation calculation. More specifically, we propose a model which allows for decentralized calculation of scores with high personalization for the user.

IFIP '21 Conference Paper · Jun 2021

Introducing Peer Copy – A Fully Decentralized Peer-to-Peer File Transfer Tool

Dennis Trautwein · Moritz Schubotz · Bela Gipp

Peer Copy is a decentralized, peer-to-peer file transfer tool based on libp2p. It allows any two parties that are either both on the same network or connected via the internet to transfer the contents of a file based on a particular sequence of words. Peer discovery happens via multicast DNS if both peers are on the same network or via entries in the distributed hash table (DHT) of the InterPlanetary File-System (IPFS) if both peers are connected across network boundaries. As soon as a connection is established, the word sequence is used as the input for a password-authenticated key exchange (PAKE) to derive a strong session key. This session key authenticates the peers and encrypts any subsequent communication. It is found that the decentralized approach to peer-to-peer file transfer can keep up with established centralized tools while eliminating the reliance on centralized service providers.

TOIT '21 Conference Paper · Jun 2021

Proof-of-Prestige: A Useful Work Reward System for Unverifiable Tasks

Michał Król · Alberto Sonnino · Mustafa Al-Bassam · Argyrios G. Tasiopoulos · Etienne Rivière · Yiannis Psaras

As cryptographic tokens and altcoins are increasingly being built to serve as utility tokens, the notion of useful work consensus protocols is becoming ever more important. With useful work consensus protocols, users get rewards after they have carried out some specific tasks useful for the network. While in some cases the proof of some utility or service can be provided, the majority of tasks are impossible to verify reliably. To deal with such cases, we design “Proof-of-Prestige” (PoP)—a reward system that can run directly on Proof-of-Stake (PoS) blockchains or as a smart contract on top of Proof-of-Work (PoW) blockchains. PoP introduces “prestige,” which is a volatile resource that, in contrast to coins, regenerates over time. Prestige can be gained by performing useful work, spent when benefiting from services, and directly translates to users minting power. Our scheme allows us to reliably reward decentralized workers while keeping the system free for the end-users. PoP is resistant against Sybil and collusion attacks and can be used with a vast range of unverifiable tasks. We build a simulator to assess the cryptoeconomic behavior of the system and deploy a full prototype of a content dissemination platform rewarding its participants. We implement the blockchain component on both Ethereum (PoW) and Cosmos (PoS), provide a mobile application, and connect it with our scheme with a negligible memory footprint. Finally, we adapt a fair exchange protocol allowing us to atomically exchange files for rewards also in scenarios where not all the parties have Internet connectivity. Our evaluation shows that even for large Ethereum traces, PoP introduces sub-millisecond computational overhead for miners in Cosmos and less than 0.013$ smart contract invocation cost for users in Ethereum.

ResNetLab Technical Report · Jan 2021

Accelerating Content Routing with Bitswap: A multi-path file transfer protocol in IPFS and Filecoin

Alfonso de la Rocha · David Dias · Yiannis Psaras

Bitswap is a Block Exchange protocol designed for P2P Content Addressable Networks. It leverages merkle-linked graphs in order to parallelize retrieval and verify content integrity. Bitswap is being used in the InterPlanetary File System architecture as the main content exchange protocol, as well as in the Filecoin network as part of the block synchronisation protocol. In this work, we present Bitswap’s baseline design and then apply several new extensions with the goal of improving Bitswap’s efficiency and efficacy and minimizing its bandwidth fingerprint. Most importantly, our extensions result in a substantial increase to the protocol’s content discovery rate. This is achieved by using the wealth of information that the protocol acquires from the content routing subsystem to make smarter decisions on where to fetch the content from.