Use Unix file system notation

[dnkolegov]

Naming subnets. We assign each subnet a name that is unique among all the children of
the same parent. Similarly to the notation used in a file system, the name of a child subnet is
always prefixed by the name of its parent. For example, subnets P/C and P/D would both be
children of subnet P.

it would be great to use UNIX notation especially if it is mentioned here: /P/C and /P/D instead of P/C and P/D.