# A Tale of Many Networks: Splitting and Merging of Chord-like Overlays in Partitioned Networks
## 5 Evaluation Results
### Evaluation Results for Setup A.1: Simultaneous Merging of Three Networks  
In Setup A.1, three different Chord rings are created, with 341, 341, and 342 nodes per ring, respectively. In two of the three rings, one node is selected to start the mergingprocedure. Thus, two nodes start to merge the third ring simultaneously. Our first goal is to determine which of the presented algorithms can merge two and more rings simultaneously without the presence of churn or network partitioning events. As we see later, this ability turns out to be important if multiple instances are started automatically whenever a present contact node is detected.  
In more complex scenarios, it happens that different rings try to merge another ring at the same time--for example, if two regions become connected again after a network partitioning event. Figure 10 shows the simulation result of three Chord rings which have been merged within Setup A.1. It can be seen that both the Ring-Unification Algorithm and our Ring Reunion Algorithm are capable of merging multiple rings without major effort and in similar time. In Figure 10b, one can see that the Chord-Zip algorithm needs more time to adjust the successor pointers than the other merging algorithms. Figure 10b also reveals that in more complex scenarios the Chord-Zip algorithm rearranges the successor pointers in a very slow tempo that would exceed the simulation time. Chord-Zip is much slower than the other solutions due to how it chooses its alternative successor pointers. While the Ring-Unification Algorithm and the Ring Reunion Algorithm preserve the correct order of nodes they merge, alternative successor pointers in Chord-Zip are always taken from the other ring and are therefore often not the best choice. Figure 10b reveals that the Ring-Unification Algorithm and the Ring Reunion Algorithm are capable of adjusting all successor pointers in complex scenarios within a short period of time.  
Evaluation Results for Setup B.1: Comparison of Gossip-Based Ring-Unification Algorithm and Ring Reunion Algorithm  
Setup B.1 is similar to Setup A.1 in the sense that two Chord rings, each with 5121 nodes per network (5120 nodes + 1 initiator), are formed at the start of the simulation. In minute 10, one node starts to merge with a contact node inside the opposite ring. As Chord-Zip is too slow to merge multiple Chord rings in an acceptable interval of time, we directly compare the Gossip-based Ring-Unification Algorithm with a fanout parameter of 4, i.e., the number of initiated mergers in each direction, to the Ring Reunion Algorithm with 4, 8, and 16 parallel instances, since those algorithms have turned out to be the fastest.  
The results of Setup B.1 are shown in Figure 11. The Ring-Unification Algorithm's advantage is that it merges a ring in two directions, clockwise and anti-clockwise. Therefore, the Gossip-based Ring-Unification Algorithm with a fanout parameter of 4 (4 instances clockwise + 4 instances anti-clockwise) can be compared best to the Ring Reunion Algorithm with 8 parallel instances (Reunion3), which outperforms the Gossip-based Algorithm. Nevertheless, the number of messages which are sent with a high number of merger instances is almost the same as the number of messages with a small number of instances.