# A Tale of Many Networks: Splitting and Merging of Chord-like Overlays in Partitioned Networks
## 2 Related Work
### Specific Overlay Types  
Geography-based overlay networks, which aim to replicate the geographical structure of the nodes, are capable of modeling the local connectivity status of the nodes. Overlays such as Geodemlia [22], FRing [23], or GeoConnect [24] structure the network topology according to the geographical positions of the nodes. Thus, connectivity is mainly local (with some shortcuts to ensure logarithmic routing complexity). These networks are easier to merge, as the responsibility of various nodes is based on their location, and there is  
Figure 3: Chord–Zip Algorithm.  
less competition in a partitioned network since no foreign node will claim geographical responsibility.  
Network partitioning in decentralized systems has varying implications depending on the overlay structure and application semantics. In blockchain-based systems, partitions can lead to severe security risks such as chain splits, double spending, or consensus divergence. Since blockchain networks are primarily concerned with maintaining a consistent ledger across a dynamic and partially connected set of nodes, any disruption of peer connectivity may lead to forks or permanent inconsistencies in the global state. Several recent works have explored the robustness of blockchain networks under adversarial conditions. PeloPartition [25] considers the case of a global Internet outage and proposes a sharding mechanism to improve blockchain resilience, splitting the blockchain into branches with the assumption that they will be merged after the network recovers. [PERSON] et al. demonstrate how a small number of targeted node removals can partition major networks like Bitcoin and Ethereum [26]. In [27], the authors show that eclipse attacks can be used to isolate nodes and manipulate blockchain views in Ethereum. [PERSON] et al. offer a broader analysis of how network partitioning affects both the security and performance of blockchain systems [28].  
A core theme in blockchain-focused networks is the blockchain itself--that is, the data stored in the network. The connectivity of individual nodes is not of high importance, as all nodes eventually store the same data. This is different in regular overlay networks, where individual nodes are responsible for objects in corresponding ID ranges. Each node carries individual data that must not be lost. Thus, connecting each node to the correct network segment is essential--unlike in blockchain-based networks, where the redundancy of the blockchain mitigates such risks.  
Peer-to-peer-based online social networks, as elaborated in a broad survey in [29], often reflect the social network ties in the overlay network topologies; this is the case in SafeBook [30], DiDuSonet [31], and Frodo [21]. The latter also shows that routing solely over a very small number of friends in a social network suffices in gaining complete connectivity. However, traffic in social networks is in contrast based on social network ties, which are different in regular ring-based structured overlays, where key-based lookups are quite evenly distributed in the ID space. Thus, p2p-based social networks might operate well in partitioned networks, as communication remains local, but ring-based overlays fail in large parts to resolve key-based lookups, as the keys and values are shut off.