Three measures, 30 notes: an introduction, then regular measures of 3, 1, and 3 doubles.
Rb ssdz ssdddsszzzb
ssd sszzzb
ssdddsszzzb
This is the "Alenchon" from the Brussels MS - the "Alenchon" in Toulouze is the same length, but has a different choreography.
I usually use the recording on Tape of Dance - it's easy to dance too, a good speed, and very pretty. There is a lovely version, but in simple duple (4/4) rather than compound duple (6/4) on Eschewynge of Ydelnesse.