JoBS performs scheduling and buffer management in a
single pass. JoBS dynamically allocates service rates to
classes in order to satisfy the delay constraints. The service rates needed
for enforcing absolute delay constraints
are allocated upon each packet arrival,
while service rates derived from
relative delay constraints are computed only
every packet arrivals. If no feasible
service rate allocation exists7.1,
or if the packet buffer overflows,
packets are dropped according to the loss constraints.
The service rates are translated into packet scheduling decisions by
an algorithm resembling Deficit Round Robin. That is, the scheduler
tries to achieve the desired service rates by keeping track of the
difference between the actual transmission rate for each class and the
desired service rate for each class. Scheduling in JoBS is work-conserving.