# Agent-Based Virtual Machine Migration for Load Balancing and Co-Resident Attack in Cloud Computing
## 6 Evaluation and Empirical Results
### Agent-Based VM Migration (ALBA) versus Centralized VM Migration
#### 6.1.2 Experimental Settings
We set the mean inter-arrival times of VMs to 5 ticks and mean inter-departure times of VMs to 100 ticks, as determined experimentally by overloading cloud computing to its maximum capacity for hosting VMs. This approach forces Sas to migrate VMs and results in VMs with a relatively long lifetime that may migrate multiple times. Agent-Based Testbed Settings  
The parameters for the experiment are presented in Table 2, which includes the VM migration heuristics of the BA and the parameters of the Sas. These parameters consist of VM migration heuristics, VM acceptance policies, VM migration thresholds, an activation threshold, and a monitoring frequency. The resource-based acceptance policies were set to 0%, which means that Sas would react to all proposals from other Sas seeking to move VMs provided that sufficient computing resources were idle. Some benchmark VM migration strategies, such as the greedy and first-fit heuristics, consider both CPU and memory utilization. To facilitate a comparison, Sas were equipped with a combined migration heuristic, which considers both CPU and memory usage. This heuristic was chosen due to its ability to achieve relatively good load balancing while achieving fewer VM migrations. To trigger VM migrations based on CPU or memory use, the resource-based migration criteria were set to 50%. Additionally, the activation threshold of Sas was set to 10 ticks, which refers to the length of time that Sas are permitted to exceed their migration criteria for computational resource usage. To ensure robustness and reliability of the simulation results, 10 different experiments were performed for each configuration of the testbed, resulting in a total of 90 simulations with the instantiation of 27,000 VMAs. Performance Indicator  
In order to evaluate the effectiveness of agents utilizing decentralized VM migration in comparison to centralized VM migration, the performance metric Balance was utilized and calculated using Equation (4). Since Sas and the central manager are required to balance VM load on the hosts, a smaller value for Balance would indicate more evenly distributed cloud computing. Analysis 2  
As shown in Figure 4, the best (lowest) two Balance indicators were found for ALBA with the round-robin heuristic (8 th column) and the greedy heuristic (6 th column). BAs assign incoming VMs evenly (using a round-robin approach) among hosts, leading to a well-balanced load. Hence, SAs can benefit from BAs' initial allocation of VMs. As described in Analysis 1, SAs can balance loads more evenly than central balancers by considering the dynamic fluctuations of VMs' resource usage. ALBA combines primary allocation of VMs (through BAs) and secondary migration (through the cooperation of SAs), allowing for optimal VM migration in cloud computing. 6. Analysis 3  
As shown in Figure 5, the central manager achieved a higher Coverage and CVR than ALBA, indicating that it is inferior to ALBA equipped with live migration in terms of security performance. It is likely that the user's reputation, i.e., security level, is not always known when cloud computing receives the user's application for a VM. The experimental design specifies that the security level of some users is known at the beginning of the experiment, while the security level of other users needs to be updated only after dangerous behaviors are detected in the VMs they own. Both ALBA and Central benefit from the initial allocation of VMs. However, the central manager does not support live migration, which results in VMs with dangerous behavior found in operation, and other VMs of the users they belong to, not being migrated to hosts with matching security levels, increasing the risk of co-resident attacks. 6.2. ALBA versus Agent-Based VM Migration without Considering CRA (MapLoad)  
6.2.1. Objectives  
The objective of this experiment is to compare the effectiveness of the ALBA load balancing method with MapLoad, an Agent-based VM migration method that disregards co-resident attacks (CRA).