A Branch node is a level in an Aggregation.
For example, an aggregation for market data traffic with 6 levels might have the following properties:
Level 1: Visibility Point (root node)
Level 2: External Group name (branch node)
Level 3: Switchport (branch node)
Level 4: Market Data feed (branch node)
Level 5: Market Data feed Side - A or B (branch node)
Level 6: Market Data feed Channel (leaf node)