This table lists the protocols that this agent has the
capability to decode and count. There is one entry in this
table for each such protocol. These protocols represent
different network-layer, transport-layer, and higher-layer
protocols. The agent should boot up with this table
preconfigured with those protocols that it knows about and
wishes to monitor. Implementations are strongly encouraged to
support protocols higher than the network layer (at least for
the protocol distribution group), even for implementations
that don't support the application-layer groups.