RESEQUENCING OF MESSAGES IN A QUEUEING SYSTEM WITH 
           HETEROGENEOUS SERVERS UNDER VARIOUS SCHEDULING POLICIES 







                                 by

                            TUGRUL DAYAR




             A thesis submitted to the Graduate Faculty of
                    North Carolina State University
                     in partial fulfillment of the
                     requirements of the Degree of 
                           Master of Science 





                           COMPUTER SCIENCE






                              Raleigh
                               1991







                           APPROVED BY:




           Matthias Stallmann               Harry G. Perros    


                          Yannis Viniotis
                   (Chair of Advisory Committee)








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                                ABSTRACT



DAYAR, TUGRUL. Resequencing of Messages in a Queueing System with 

Heterogeneous Servers Under Various Scheduling Policies. (Under the direction 

of Yannis Viniotis.)

   In a store and forward communication network, packets may go out of order

when multiple links are used between intermediate nodes. Since packets

arriving at the receiver node have to be put in order, each packet incurs a

resequencing delay in addition to transmission and queueing delays. A

threshold-type scheduler, a FIFO scheduler, and a two-level scheduler are

studied. The effects of these scheduling policies on average end-to-end delay

per packet are investigated for a single node with bursty arrivals and

variable length packets. The results obtained through simulation for the

three different schedulers are compared and it is shown that the threshold-

type scheduler gives the best performance.