The data here is sourced from the 2012 version of the BP Statistical Review of World Energy, specifically the "Gas - Trade - pipeline" and "Gas - Trade movement LNG" worksheets. If you download the Excel spreadsheet, you'll see that the data is represented as a matrix. While this format makes it easy to sum up the amount of gas moved to and from specific countries, it does not provide an easy way to quickly understand the structure of these trade networks.
The visualization below uses this data, but draws the network dynamically using a query that retrieves information on where gas flows are going to and from, in addition to their modality (LNG or pipeline), along with the volume of the flow.
http://is.gd/gasflows is the shortened URL for this page.