MARCO CONCEPTUAL

VMs are a good alternative to use when there are limited physical machines available because they virtualize the components of a real machine, like the processor, buses, and peripherals, and a full operating system. Software testers are attracted to using VMs since they can easily test software on a variety of systems without having to configure and run a full physical machine. There are two main companies that provide free virtualization: VMWare and VirtualBox [41] [42]. VMWare is a leading virtualization company that provides services across all levels, from the home user to large businesses. . VMWare Player is their free virtualization solution for home users. VirtualBox is an open source virtualization solution from Oracle that provides the same

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services as VMWare player. It has more flexibility and configuration options than VMWare Player. VMWare has solutions that have the same flexibility and configuration control, but these solutions are not free.

VMs were used to do the IPv6 evaluation of OPNET Modeler and SITL. VMWare Player was chosen as the virtualization agent as it provided the most stable network configuration through initial trials. The VirtualBox solution was tried, but full communication with the machines and simulation was never achieved. The network bridging mechanism of VirtualBox was determined as the problem area as other means of networking (Network Address Translation and a host-only network) worked correctly.

There were three VMs made to be used for the IPv6 OPNET evaluation. Two VMs used the Ubuntu 11.10 operating system (OS) which supports IPv6 and can be easily configured to run a webserver. Wireshark [23], a packet capturing tool, was loaded onto these machines to help monitor packets across the network. The third machine ran Backtrack 5, a penetration testing Linux distribution [43]. Backtrack 5 contains several packet crafting tools that were used for the IPv6 extension header tests. Each VM has its virtualized network interface bridged with one of the USB NICs. The configuration between VMs and the simulation on the host machine is shown in Figure 5.1.

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Figure 5.1 Configuration of VMs on a Host Machine

The SITL process was configured with the NIC bridged with the VM and packet filter. The packet filter followed the same syntax for each SITL node:

ip6 and (ether src <Virtualized NIC MAC address> or ether src <USB NIC MAC address>).

There are three main parts to this filter the first of which is “ip6.” This part is intuitive; the filter allows IPv6 packets through to simulation while dropping IPv4 packets. The second part is “ether src <Virtualized NIC MAC address>” which filters for packets containing the Virtualized NIC Ethernet address as the source address. The third part is ether src <USB NIC MAC

address>.” It only allows packets with the USB NIC Ethernet address as the source address though to simulation. These three parts completely form the filter that allows for the correct packets to be translated into simulation and any unrelated packets to be dropped. The SITL NIC and packet filter set in the attributes menu is shown in Figure 5.2.

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Figure 5.2 SITL Attributes Menu

There are two main benefits to using VMs to host an application and generate packets. The first benefit is that extra machines are not need. The entire set of components for simulation can be contained on one physical machine providing that the host machine has free space for the VM files which allows more control over the system settings, particularly network interface

configuration. The second benefit is that configuring of a new VM is fast and simple. VMs are easily duplicated so only one full configuration of a VM is needed if all the VMs have the same parameters. If the OS is a variable in the simulation, then new VMs with different OSs can be configured quickly without having to worry about compatibility with physical hardware.

The VM configuration has limitations as well. The biggest limitation of using VMs is that the host machine must have enough memory resources to contain the memory it uses and the memory of the VMs. Since VMs take up space on a host machine, the simulation performance can be affected. One possibility is that the simulation has a smaller space to grow which affects the performance. Simulations with a large amount of events will take longer to execute and have the potential to abort the program entirely. Another effect is that there is a measureable delay

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when transferring packets between the network interfaces. This extra time of passing packets between the virtualized network interface to the USB NIC adds to latency. The additional latency was made clear in a comparison ping flood test between using VMs and real machines. The VM configuration averaged 14.88ms for a 50,000 packet ping flood over 10 iterations. The real configuration averaged 2.04ms with the same test. The results of this comparison test are summarized in Figure 5.3. The observed additional latency was one of the determining factors for not choosing the VM configuration for the IPv6 application testing.

Figure 5.3 Comparison Ping Flood Test Results