1. Native simulation of priority queue system
TELE 4642: Network Performance: Project 
Native simulation of priority queue system By
Bahador Pazokifard
Vipoom Vimonses
Semester 1 / 2011
School of Electrical Engineering and Telecommunications
University of New South Wales

2. Outline: Introduction of Priority queue What is priority? In General
In Network
Why do we use it?
Why is it important?
Simulation

3. QoS prioritize the network traffic
-works by delaying service for unimportant(or less important) packets, or in the cases of extreme network traffic, discarding them entirely.
-works by leaving room for important packets to reach their destination as quickly as possible

4. Queues
Queues without priority : elements are stored in First-come-first-served order(FCFS) 𝜆1
Server 𝜆2
Queues with priority : elements are pulled highest-priority-first
A priority queue must at least support the following operations:
add an element to the queue with an associated priority
remove the element from the queue that has the highest priority, and return it
𝜆1(high priority)
Server
𝜆2 (low priority) 𝜇
Example:
-Hospital bed management
-Internet traffic routing

5. Priority in queues Types of priority in queues:
Preemptive-resume priority
High priority has absolute priority over low priority;
High priority can interrupt the low priority service.
Non-preemptive priority
The service cannot be interrupted;
High priority has nearly absolute priority over low priority .

6. Simulation
Our project is about the simulation of non-preemptive priority queues: λ1
Input Queue Without priority
𝜇=1sec
……. 1 1 1 1
Server .. 2 1 2 1 1 2 1 2
SERVER 2 1 2
……. 2 2 2 2 λ2
Random selection of type-1 and type-2 customers and placement of them into the input queue 1

7. Simulation 𝜇=1sec 2 𝜇=1sec Input Queue Without priority Server .. 2 2
With priority
𝜇=1sec
Server
...
... 2 2 2 1 1 2 2 2 1 1 1

8. Simulation
The server starts working and waits for the arrival of the packets. The time that the server spend on every packets is μ = 1 sec.
Randomly choose type-1 and type-2 packets and store them on the input queue.
Type-1 &Type-2 customers arrive to the server respectively with the rates of λ1 and λ2.
At this part, packets are stored in a queue with priority, which puts the type-1 customers in front of the other type-2 customers.
Now that the server has a packet to serve, it starts to pop the packets off the input queue and store it to the output queue.

9. Conclusion Problem that we faced during the simulation:
The simulator runs the program line-by-line, but we have to run the server and the input queue simultaneously, which can not be done at the same time! Implementation of threads in our simulation
Future works(suggestions for future students):
-Non-preemptive priority for more than 2 types of customers
-Preemptive-resume priority for 2 types of customers
-Preemptive resume priority for more than 2 types of customers