The maximum number of modules and sub-modules (different levels) that
can be associated with a slot number in the system. This value is
constant for a particular hardware platform family. The number of
levels is 2 for a first generation E-series (ERX) platform and is 4 for
a second generation E-series platform.
For the first generation E-series (ERX) platform family:
level 1 - SRP or line card module
level 2 - I/O adapter module
For the second generation E-series platform family:
level 1 - Forwarding module or SRP sub-module
level 2 - Switch fabric slice (SFS) sub-module or module
level 3 - Bay 0 I/O adapter
level 4 - Bay 1 I/O adapter