Priority Queuing
Done by:Shahad H. Zwayen
FCFS queuing discipline
M/M/1 with FCFS queuing discipline
Impatient Customers! (problem)
Solution??
Priority Queuing
A packet's priority class may depend on:
1. Explicit marking that it carries in its packet header (e.g. ToS) bits in an IPv4 packet)
2. Its source or destination IP address.3. Its destination port number.4. Other criteria
M/M/1 system with dual priority
PQ types:1- preemptive2- non preemptive
Preemptive scheduling discipline
Preemptive priority queuing (2- classes)
Class 1
Class 2
𝜆𝜇
𝜇
𝜆1
𝜆2
State transition diagram
Performance measures
Non-preemptive scheduling discipline
Non-preemptive PQ:
Non-preemptive performance measures
Example:Let as consider a router forwarding two types of packets Video and audio.For = 0.2, = 0.6 and the processing time = 1 sec.
Solving.…
In case of all packets are processed in order of arrival
In case of video packets have absolute priority over audio packets (Preemptive)
Performance measures for audio packets
In case of video packets have Non-Preemptive priority over audio packets
REFERENCES• Queueing Systems, Ivo Adan and Jacques Resing,
March 26, 2015.• Analysis of M/M/n/K Queue with Multiple
Priorities, Sanjay K. Bose, 2002.• IJCIT, Multiple Services Scheduling with Priority-
Queuing Model, Peng Ke, YuanXiang Li and FuChuan Ni, ISSN 2218-5224.
• Multi-server queueing systems with multiple priority classes, Mor Harchol-Balter, Takayuki Osogami, Alan Scheller-Wolf, Adam Wierman.
Thank you
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