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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