Specifies the whether the link should be drawn with one or two arrows.

A 'standard' (twoway) link has two arrows - one for inbound data and one for outbound data. In some situations (e.g. round-trip latency), you might only want an arrow in one direction.

One-way arrows only show the outbound BWLABEL, but they show it in the standard position - 25% of the way along. Change the position of the label with BWLABELPOS as usual (you still need to specify two positions in the BWLABELPOS line, however).