public final class ProtocolStack
Maintains a protocol per thread. Each thread has a authenticated subject
and a protocol to go along with it. We use the thread protocol to establish
a connection to the remote peer. The protocol has QoS information in it.
A protocol is pushed into the thread whenever a security subject is pushed.
The protocol is popped when the corresponding subject is popped. It would
have been ideal to put the protocol in the subject itself but we cannot
do that for compatability reasons.