An analytical model for churn process in Bitcoin network with ordinary and relay nodes
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An analytical model for churn process in Bitcoin network with ordinary and relay nodes Saeideh G. Motlagh1 · Jelena Miˇsi´c1 · Vojislav B. Miˇsi´c1 Received: 23 March 2020 / Accepted: 18 June 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Dynamic participation of nodes, also known as churn, is quite common in P2P networks, and Bitcoin network is no exception. The impact of churn becomes more pronounced when nodes with different roles and functionality exist. In this paper we analyze node churn in Bitcoin network where ordinary nodes generate transaction traffic and distribute and verify blocks, while relay nodes that just distribute blocks, but have a larger number of connections. We use the tools of probabilistic analysis and Markov chains, and show that churn of relay nodes has a higher impact on traffic performance than that of ordinary nodes. We introduce two different Continuous Time Markov chains (CTMC) for ordinary and relay nodes to model each type of node’s behavior separately. Our results indicate that node sleep impacts the performance more in networks where the proportion of relay nodes is lower, and also that block and transaction delivery times are higher in those cases. Also, we find that the time needed for a node to synchronize upon rejoining the network after sleep is dominated by the time required for block and transaction verification. Keywords Bitcoin · Node churn · Relay nodes · Performance evaluation
1 introduction Blockchain is a decentralized ledger in the form of a linked list of blocks [20]. It provides a secure, decentralized and immutable platform to store and track the data. On account of this it has been used in many applications such as supply chain management [26], energy trading [27], and cryptocurrencies such as Bitcoin and Ethereum [28]. Moreover, blockchain has been used to improve the existing technologies including cloud [29, 30], Internet of Things (ToT) [31], big data [32], and others. Bitcoin is a blockchain-based electronic payment system that keeps track of financial transactions. It is a permissionless system which individual nodes may join or leave at will, thus creating the so-called churn which is common in P2P networks [25]. As the Bitcoin network grows, churn will only become more pronounced: for example, powerful commercial servers used for Bitcoin mining overnight are needed to conduct regular business during working hours [18], while nodes located in developing countries may Vojislav B. Miˇsi´c
[email protected] 1
Ryerson University, 350 Victoria St., Toronto, ON, Canada
experience random interruptions of electricity supply which affects their presence [12]. The dynamic architecture impacts traffic propagation in two ways. First, nodes that are absent do not participate in traffic relaying and distribution. Second, nodes that rejoin the network need to synchronize their blockchains with the rest of the network; in doing so, they require the assistance of their peers. In both cases, propagation delays increase due to the
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