Head of Line (HOL) Priority Queuing

Posted by AJ × 08:27

• Second queue scheduling approach which defines number of priority classes.

• A separate buffer is maintained for each priority class.

• High priority queue serviced until empty and high priority queue has lower

waiting time

• Buffers can be dimensioned for different loss probabilities

• Surge in high priority queue can cause low priority queue to starve for resources.

• It provides differential QoS.

• High-priority classes can hog all of the bandwidth & starve lower priority classes

• Need to provide some isolation between classes

Sorting packets according to priority tags/Earliest due Date Scheduling

• Third approach to queue scheduling

• Sorting packets according to priority tags which reflect the urgency of packet needs to be transmitted.

• Add Priority tag to packet, which consists of priority class followed by the arrival

time of a packet.

• Sort the packet in queue according to tag and serve according to HOL priority

system

• Queue in order of “due date”.

• The packets which requires low delay get earlier due date and packets without

delay get indefinite or very long due dates

All Syllabus