Scale of the Previous Design
Originally a flat network - one layer of routers interconnected over a complete PVC mesh.
A Network “event” in 1998 on AS3561 “educated” the engineering staff on IGP scaling issues.
This “event” lead to a week of network instability as it was re-engineered.
At one time there were 380+ routers in the direct mesh, accounting for 30k PVCs in the network & 760+ direct IGP associations per router.