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Emulated Network at the Virtual Wall

If the influence of the network is important in your experiment, the Virtual Wall testbed at IBBT offers you capabilities to control different network-oriented aspects. The functionality can be summarized into three main categories:

  • Network topologies: the Virtual Wall allows you to setup any network topology you want and, by default, provides shortest path routing between any compute resources installed on the network nodes, with Gigabit connectivity.
  • Network impairments: if you want to study the influence of network impairments on the performance of your system under test, you can specify link characteristics such as bandwidth, latency and loss rate on each link, both statically and dynamically.
  • Background traffic: it is also possible to introduce TCP or UDP streams on the links to represent background traffic, with parameters to identify the protocol used, the packet size and the throughput.

Network Topologies

On the Virtual Wall infrastructure, a lossless switch with 1000 1Gbps ports interconnects all 100 nodes, each with 4 or 6 1Gbps ports, via VLANs. Each experiment on the Virtual Wall can use a subset of these nodes and connections to create a network topology. On each of these nodes default or customized images can be swapped in. The links have a default bandwidth of 1Gbps. Details on how to start an experiment on the Virtual Wall can be found on How to run experiments on Virtual Wall (ibbt-vw).

Network Impairments

During experiment preparation, different values can be set to the parameters of each network link, to introduce impairments. The bandwidth of the link can be reduced from 100Mbps to any lower value. The latency can be increased from 0ms to several tens (e.g. access network link) or hundreds (e.g. Internet backbone link) of ms. Packet loss can be introduced as well, with typical values of several % for access network links or several tens of % for Internet backbone links.

These impairments can dynamically be updated during the experiment run. Details on network link configuration can be found in Overview of Networking in BonFIRE.

You can also set a specific queue strategy. By default the DropTail strategy is used, but you can also use either RED or GRED. Both these strategies expect a few other parameters, which can be found in Basic network resources

Background Traffic

In order to determine the influence of background traffic on the tested system, transport layer streams can be created on each of the network links. These streams can use the UDP or TCP protocol, which can be chosen through the “protocol” parameter. The bandwidth of the stream can be controlled by setting the other two parameters for packet size (in bytes) and throughput (in packets per second). Details on background traffic configuration can also be found in Overview of Networking in BonFIRE.

How to Emulate Network at the Virtual Wall

There are different possibilities to emulate network at Virtual Wall.