Figure 1. Design of the original vertebrate biodiversity networks, some of which are still active today, used a three-tiered system in which portals are connected to a layer of servers using the DiGIR protocol.

This architecture requires hundreds of individual servers and hundreds more connections between them and the portal. The result is a network in which each element is a potential point of failure. The six portal servers consisted of the four shown and two additional mirror portals for the Mammal Networked Information System (MaNIS). Key: M = MaNIS, O = ORNIS, H = HerpNET, and F = FishNet II.