iMinds iLab.t Virtual Wall

What the Virtual Wall is used for

The Virtual Wall testbed contains 300 physical servers which are fully configurable both in terms of their software installation  (e.g. choice of operating systems, drivers, applications, etc.) as well as how their (Ethernet) network interfaces are physically interconnected. The Virtual Wall has no "default behavior", but can -within minutes- be set up as a reliable and repeatable platform to meet a wide variety of testing and experimentation demands. Example scenarios where the virtual wall is used include:

  • Use as a fully configurable and repeatable sandbox environment for prototyping and evaluating new ICT-solutions (e.g.. "give me access 50 physical Linux servers, interconnected like this (...), with a delay of x ms on links y and z") 
  • Replication of existing ICT solutions for further analysis (e.g. "give me 10 servers, install following software on server 1/2/3 so they behave as my distributed back-end, I will use 7 other servers to mimic client demands in my set-up, then vary the load generated by these from very low to very high, and measure the response times") in a repeatable way ("I improved the implementation of my back-end and want to its performance in the same way as I did last month").
  • Use as emulated (virtual) clients for a solution hosted/running in the public internet or for third-party equipment (temporarily) hosted at iLab.t
  • Use to validate novel network protocols in complex network set-ups
  • Use for training purposes or to support educational activities (e.g. "I want my students to gain some practical experience with computer networks, e.g. for them to be able to configure DHCP server, web server, subnets, ..., I would need 20 configurations of  4 computers, each to operate independently, configured like this (...) and available next Friday from 09:00 to 12:00").
  • Use to emulate the behavior of networks that are hard/expensive to access (e.g. configure certain links in the Virtual Wall set-up to suffer from a certain amount of packet loss and delay, emulating e.g. transatlantic cables or satellite uplinks).

When needed needed, the Virtual Wall can be interconnected to other devices inside or outside the lab.  As long as servers are available, several people or groups of people can work on their own set-ups without interfering with each other.

Behind the scenes - how does the Virtual Wall work?

Two Virtual Wall set-ups are available: Wall 1 is built out of 200 physical servers: 100 x quadcore, 100 x eight cores; Wall 2 contains 100 physical servers: 100 x 12 cores. All servers are equipped with a management Ethernet interface, and multiple (4 to 6 for the quad cores, up to 11 for the 12-cores) Ethernet interfaces that can be used for experimentation purposes. The servers can be interconnected in any imaginable way because all of the Ethernet interfaces are pre-wired and connected via large switches acting as patch panels.

The Virtual Wall is controlled by testbed management software (based on Emulab).   After selecting which operating systems/packages/configurations/... are required,  the control software contacts the different servers and installs the demanded software configurations (this is called "swapping in"). In addition to configuring the physical Virtual Wall servers as (virtual) server(s) part of the solution under test or (virtual) client(s), the software may also configure certain servers to behave as a network element (e.g. a controllable lossy link with configurable bandwidth and delay).  The control software also takes care of enabling the requested network configurations by reconfiguring the large switches. This results in endless emulation and experimentation possibilities.

What does it look like?

Below is a picture of the Virtual Wall 1 set-up.  The servers are located in the bottom of the racks, the Virtual Wall 1 switch in the middle. Virtual Wall 1 also makes available a set of screens which can -for example- be used to get a qualitative assessment of how video is affected while being transmitted through a network.