Computer Networks :: Technology, Network Resources

Computer networks like internet necessitate network resources, i.e. bandwidth, buffer spaces, etc in order to accommodate the arriving packets at router buffers [25]. When the arriving packets cannot be accommodated due to lack of network resources, this indicates occurring congestion at router buffers of networks [21]. Congestion can deteriorate a network performance [22, 25] through growing the packet loss probability due to overflow as well as the mean waiting time for packets in the queueing network. In addition, congestion may reduce the throughput and increase the packet dropping probability precedes the router buffers have overflowed. Congestion can also generate unmaintained average queue length ( ), and this may lead to build up the contents of router buffers, and thus many arriving packets may drop or lose at the router buffers. Many researchers have proposed methods with aim to control congestion at router buffers of networks [1, 2, 4, 5, 8, 14, 15, 16], i.e. AQM methods [1, 2, 4, 5, 6, 7, 8, 13, 14, 15, 16]. Each AQM is proposed as a congestion control method that identifies congestion at router buffers in an early stage, which means before the router buffers have overflowed. The most known AQM method is RED [14], Gentle RED [16], the Adaptive GRED [2], Adaptive RED [15], Random Early Marking (REM) [7], Dynamic Random Early Drop (DRED) [8] and some discrete-time queue analytical models [1, 4, 5, 6] which were constructed depending on some of AQM techniques. For example, DRED analytical models which they constructed by analysing two queue nodes [5] and three queue nodes [1] based on DRED and using discrete-time queues mechanism [26]. GRED analytical model [4] and BLUE analytical model [6] were constructed depending on GRED and BLUE, respectively and utilising discrete-time queues mechanism. As mentioned previously, RED was proposed as a congestion control method, but RED can degrade the network’s performance due to the following causes: 1) abruptly RED can increase its arrival rate aggressively, thus the RED’s router buffers may overflow. Therefore, every arriving packet will lose. 2) At a particular time, the RED’s congestion measure ( ) value may be below the value of minimum threshold position at the router buffer ( ). This indicates no packet can be dropped. However, for a short time the arrival rate increases and making the router buffer overflowing. Nonetheless, the value increases but still smaller than the value of .