SupplyChainNode object
A SupplyChainNode identifies one system in a supply chain: the advertising system's domain, the seller account inside that system, and whether the node takes part in payment. Nodes appear in order in SupplyChain.nodes, one per hop.
How it is used
A buyer verifies a node by fetching sellers.json from the domain in SupplyChainNode.asi and looking up SupplyChainNode.sid as a seller_id there. The first node of a complete chain should also match a line in the publisher's ads.txt or app-ads.txt. The optional name and domain fields exist only for sellers that sellers.json does not describe.
The Supply chain (schain) page covers it in more depth.
Fields
Where it sits
Contained in: SupplyChain.
All objects
The field reference index lists every OpenRTB 2.x object.