Where was a small settlement of arikamedu​

Puducherry
Arikamedu is an archaeological site in Southern India, in Kakkayanthope, Ariyankuppam Commune, Puducherry. It is 4 kilometres (2.5 mi) from the capital, Pondicherry of the Indian territory of Puducherry.

An informal structure in a bureaucracy would be something like so-called "office politics". where there's a formal structure set up for the organization, but then an informal subculture as well that has a way of organizing the bureaucracy further. this can be positive because it sets up an added degree of organization, albeit informal, within the bureaucracy.