How to add interfaces details on link

• In your second example on link between SJC-1 and SJC-2, one side is labeled 3500 and other is 5500.
• how to change it to e5/2 on one side and e3/4 on other and using link property. 
• The link property is also used to describe additional information about the link such as interface/bandwidth/link type.

you can change this two any properties in configuration, that from your link data, like 'model.sourceInterface' or 'model.linkBandwidth' etc

  sourcelabel: 'model.srcTrafficMap.Default.EMPTYQUEUE', targetlabel: 'model.tgtTrafficMap.Default.EMPTYQUEUE'

• What is the significance of EMPTYQUEUE? Is it a reserved word?

    There's no importance. That's just a part of example above. What follows "model." is 100% up to you.

• This doesn't seem to work if one of the nodes is inside a nodeset. 

This is a normal behavior, because the nodes were hidden inside the node set, which prevents any additional info to be shown. (Otherwise, there could have been way too many labels, overlaying each other...) Once you expand the node set, the interface details show up -- which makes sense, because at the same time you can see both a node and the label.