  Communication networks need to support voice and data calls simultaneously.
This results in a queueing system with heterogeneous agents. One class of
agents demand immediate service, would leave the system if not provided. The
second class of customers have longer job requirements and can wait for their
turn. We discuss the achievable region of such a two class system, which is the
region of all possible pairs of performance metrics. Blocking probability is
the relevant performance for eager/impatient class while the expected sojourn
time is appropriate for the second tolerant class. We obtain the achievable
region, considering static policies that do not depend upon the state of the
second class. We conjecture a pseudo conservation law, in a fluid limit for
eager customers, which relates the blocking probability of eager customers with
the expected sojourn time of the tolerant customers. Using this conjecture we
obtain the static achievable region. We validate the pseudo conservation law
using two example families of static schedulers, both of which achieve all the
points on the achievable region. Along the way we obtain smooth control
(sharing) of resources between voice and data calls. We also consider an
example dynamic policy to establish that the dynamic achievable region is
strictly bigger than the static region, for this heterogeneous queueing system.
