A series of simulations were performed on both the Mark I and the Mark
II network from 1968-1975. The first set of studies performed on the network
was in 1966 when Scantlebury and his group researched the feasibility
of a high-level network.
Afer Scantlebury's work, Roger Healy assumed the responsibility of
the studies until 1970 when Plessey Telecommunication Research (PTR)
undertook the responsibility.
A adaptive routing strategy was chosen for the NPL site, which was
based on Baran's hot potato scheme. Healey's study showed that as "network
traffic increased, congetion occurred, which eventually can lead to
network failure. Healey's study was done in isolation, but research
by PTR confirmed his findings.