# A Tale of Many Networks: Splitting and Merging of Chord-like Overlays in Partitioned Networks
## 4 Evaluation
### Simulation Setup
\begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt}} \hline \multicolumn{2}{c}{**General Settings**} \\ \hline Simulator details & PeerfactSim.KOM [36; 37; 38], 10 seeds per setup \\ Network model & GNP [39], jitter based on [40], no packet loss \\ \hline \multicolumn{2}{c}{**(A) Simultaneous Merging of Three Networks**} \\ \hline Algorithms & Chord–Zip [6], Simple Ring Unification [7], Gossip-based Ring Unification [7], Ring Reunion (1 and 4 instances), no churn \\ \hline A.1 Three rings & 0 min: setup of 1024 nodes in three Chord rings (A: 341, B: 341, and C: 342 nodes). From 10 min: merge algorithm started by passing random nodes from A and B to one node in C. 180 min: simulation end. \\ \hline \multicolumn{2}{c}{**(B) Direct Comparison of Gossip-based Ring Unification [7]**} \\ \multicolumn{2}{c}{**and Ring Reunion with Various Instances**} \\ \hline Algorithms & Gossip-based Ring Unification (4 + 4 instances), Ring Reunion (4, 8 and 16 instances), no churn \\ \hline B.1 Two large rings & 0–150 min: setup of 10,242 nodes in two Chord rings (each with 5121 nodes). From 10 min: merge algorithm started by adding one connecting link. 180 min: simulation end. \\ \hline \multicolumn{2}{c}{**(C) Testing of Various Approaches to Identify Contacts in Other Overlays and to Start the Merging Process**} \\ \hline Algorithms & Chord–Zip [6], Simple Ring Unification [7], Gossip-based Ring Unification [7], Ring Reunion (1 and 4 instances), no churn \\ \hline Scenario & 0–150 min: 1024 nodes join two different Chord rings (each with 512 nodes). From 180 min: 310 nodes (in one country) are isolated. 240 min: isolation is canceled, all nodes are reachable. 360 min: simulation end. \\ \hline C.1 Passive list & Maintaining a list of previously online nodes, which is checked every 3 min. If active node is found, start merging process. \\ \hline C.2 Public list & Publicly known 160 contacts are tested every 4 min in iteration. Once an active contact is found, the merging process is started with probability 1. \\ \hline C.3–5 Public list, dynamic probability: Gossip, Reunion2 & Nodes maintain a list of 160 nodes which is obtained from bootstrap node during join process. Checking online presence of a random node in this list every 4 min. Start merging process with probability of \(a/size\), where \(size\), is the estimated number of nodes in the current construct. \\ \hline \multicolumn{2}{c}{**(D) Complex Scenario Using the Public List Approach**} \\ \hline Algorithms & Gossip-based Ring-Unification Algorithm [7] and the Ring Reunion Algorithm (1 and 4 instances), public list with \(a=10\), no churn \\ \hline D.1 Complex rings & 0–150 min: setup of 1024 nodes in one Chord ring. Group of 400 nodes is isolated in 180–240 min. Group of 50 nodes is isolated in 200–2400 min. Group of 100 nodes is isolated in 240–300 min. 360 min: simulation end. \\ \hline \multicolumn{2}{c}{**(E) Parameter Studies and Churn**} \\ \hline Algorithms & Ring Reunion (8, 16, 32, 64 instances), public list, churn enabled \\ \hline Scenario & 0–150 min: 1024 nodes join Chord ring. From 180 min: 400 nodes become isolated. 240 min: isolation is stopped, all nodes are reachable. 360 min: simulation end. \\ \hline \multicolumn{2}{c}{E.1 Changing \(a\) and Instances} & Algorithm is combined with \(a\in\{10,100\}\). The interval with which the _public list_ selects a merging candidate is set to 5 min. \\ \hline \multicolumn{2}{c}{E.2 Changing frequency of merge attempts} & Algorithm combined with intervals of 5, 10, 15, and 20 min in which merger instances are started, to find compromise between operation time and bandwidth consumption. \\ \hline \end{tabular}
\end{table} 
Table 1: Simulator setup and scenario setups. global Chord ring. In the 180 th minute, a group of 310 nodes is, due to an isolation event, separated from the other nodes. During the isolation, nodes in both separated regions search for other reachable nodes in order to start the merger algorithm. In minute 240, the isolation is canceled so that all nodes are reachable again.