Sequence numbers are used when generating messages if the
KRB5_AUTH_CONTEXT_DO_SEQUENCE (x'00000004') flag has been set in the
authentication context.
The Kerberos protocol runtime provides no concurrency control for the
authentication context. If the application wants to use the same authentication
context in multiple threads, it is the responsibility of the application to
serialize access to the authentication context so that only a single thread is
accessing the authentication context at any time.