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Modified Random Early Detection Algo Research Journal of Computer and Information Technology Sciences _______________________ ISSN 2320 – 6527 Vol. 5(3), 1-6, May (2017) Res. J. Computer and IT Sci. Modified random early detection algorithm to enhance the performance of bursty network traffic Anup Kumar Sharma * and Ashok Kumar Behera Department of CSE, Bhilai Institute of Technology, Durg, India [email protected] Available online at: www.isca.in Received 10 th April 2017, revised 16 th May 2017, accepted 19 th May 2017 Abstract Reduction in the delay of the network traffic is an important problem in the communication network. But, it becomes hard to bring down the delay with boosting the performance. The reason for this, to minimize the delay there must be a small queue but to reduce the packet drop there must have a large queue. In our proposed modified RED, the Explicit Congestion notification marked and network traffic packets will be dropped when only excess congestion occurs at router in TCP/IP network. The main aim is to provide better congestio n control over the bursty traffic with maintaining the advantages of RED. Due to exponential increases in network traffic, to minimize the increasing packet loss rates, the IETF (Internet Engineering Task Force) consider the establishment of AQM techniques such as RED, REM. We use ns2 to simulate the modified RED and demonstrate that the modified RED gives better delay reduction and higher link utilization in case of bursty network traffic. Keywords: Random early detection (RED) , Congestion control, Active queue management (AQM), Bursty traffic, Drop tail. Introduction To resolve the problem, like full queue problem, with tradition al queue management mechanisms, we have active queue The typical queue management technique for router, drop tail management techniques 8. These are proactive approach, means and random drop were used with the TCP, that fixes the buffer they start dropping the packets before buffer limit is reached, size as maximum buffer size for every router. Router accepts the because of this, sender is notified before the queue becomes full packet till the buffer becomes full, afterwards it starts dropping and may respo nd much earlier about the congestion. Lock out of newly arriving packet. This mechanism is termed as Drop problem can be resolved by using other queue management Tail. This mechanism has various disadvantages. The two -main technique like random drop, because the packets are dropped 1 important disadvantages . Firstly, Lock-Ou t Problem; In this it from various flows rather than a single flow in these might be possible that, drop tail grants one or some more flows mechanisms. In this paper, we have desi gned a modified to occupy the full queue space. Because of this it stops technique for packet drop with the help of RED algorithm and alternative flows from getting space in the queue. Other have compared with traditional packet drop technique in bursty drawback is full-queue problem; this problem occurs when the network traffic. queue becomes full or it is very nearly to full. This results in delay for packet delivery from source to destination. Motivation for modified red Many AQM techniques has been proposed in past years2. The RED has indeed many enhancements over conventional Random early detection algorithm makes use of average queue mechanism but stil l it has some limitations regarding stability, size to tackl e with the problem in traditional mechanisms for scalability, complexity in parameter setting and ease of congestion avoidance and control 3. Adaptive virtual queue deployment. Many researchers proposed various methods to (AVQ) is another mechanism which introduced a virtual queue overcome these issues. Random early detection gateway drops length whose capacity is less than actual link capacity 4.Another the packet in two distinct ways: In first way, packet is dropped AQM mechanism is Random exponential marking(REM),which when there arises buffer overflow secondly, packet is dropped is very similar to RED mechanism except the way congestion is or marked when the queue size surpasses the max threshold or measured and with a different marking probability function 5. random nature of dropping probability 9. So, for improvement in this mechanism, we must have to identify these dissimilar ways REM tries to attain negligible delay and high link utilization by of packet dropping. In first way, we need to drop the packet decoupling performance measure fro m congestion measure. without intimating directly to the sender regarding the Aweya J. et al. suggested a method to improve the effectiveness occurrence of congestion. Second way in RED drop, packets of RED mechanism by dynamically altering the threshold may be marked instead of dropping or can be transmitted. T he settings when the number of connections changes 6,7 . host can regulate his window size correspondingly. International Science Community Association 1 Research Journal of Computer and Information Technology Sciences ___________________________________ ISSN 2320 – 6527 Vol. 5(3), 1-6, May (2017) Res. J. Computer and IT Sci. Sender gets notified about the occurrence of congestion by the RED algorithm can be described as follows: timeout or reception of duplicate ack of the sent packet. A RED Algorithm mechanism for controlling the congestion is said the be good if Calculate average queue size avg L it slow down the network delay, which can be obtained by If avg L< min th retaining the avg buffer size small 10 . Most of the simulation enqueue packets results show that buffer overflow is the most significant cause else if min th ≤ avg L< max th for packet drop at the router in RED, particularly in the case of compute probability P a high traffic. A very important question in congestion avoidance with probability P a mechanism is the approach being applied to find out the packet Mark or drop packets from the queue dropping probability. In RED algorithm, average buffer size is else opted in calculation the packet dropping probability. But the with probability 1-Pa problem in RED mechanism is that average buffer size changes enqueue packets very often because of dynamic traffic. In this condition, the else if avg L ≥ max th packets are being dropped unnecessarily just because of discard packet overflow. This situation may result in timeout between the two end parties which lowers the performance. The entire above problem with RED encourages us to develop an enhanced mechanism To overcome these problems of RED, we choose persistent which doesn’t forces to drop the packet because of overflow. flows as an alternative of ephemeral flows for drooping of Also, it is required from the enhanced mechanism to keep the packets. Packets will be dropped only when there arises high useful characteristics of random early detection algorithm. congestion at the router in TCP/IP Network in the proposed mechanism 12 . Modified random early detection algorithm This method is applicable with all the Active queue Generally, we observe some problems in AQM techniques. The management techniques. An enhanced mechanism has been two-main problem can be described as follows: Firstly, the proposed based on the random early detection mechanism in AQM algorithm treats equally, traffic from all the different this paper. In this random drop and front drop are also modified. flows but in actual the internet traffic remainsmomentary 11 . Drop tail cannot be improved due to extra overhead in finding Also, congestion window of short lived traffic is small. non-ECN marked or miced packets. Therefore, in short lived flow dropping of packet not reduces congestion that much. RED Algorithm (Modified) For each arriving packet: Secondly, Congestion is notified to sender by dropping the if avg <= min then packet or by marking explicit congestion notification bit of L th enqueue packets header in the IP datagram. If marked datagram is considered for end prior drop, transmitter find out congestion a little late which if avg >= max then slow down the transmitter to put its window to suitable rate. L th Discard packets end RED algorithm is the widely deployed and most popular AQM if min <avg < max then technique. RED algorithm is the techniques used for congestion th L th if Mice == 1 or ECN == 1 then avoidance at the gateway. It also detects the congestion and enqueue packets notifies the sender about the congestion. The random early end detection gateway has been implemented to monitor avg buffer Drop or mark the packets with probability P size for every queue, and selects arbitrary connection to notify a end about the congestion. RED algorithm consists of following important parameter: i. Simulation Environment Average queue size: It gives the average size of the queue. It is The proposed modified RED algorithm has been simulated in measured in packets or bytes and denoted as avg L. ii. Maximum Threshold: It is the upper limit of the buffer after which all the the simulator, NS2 and the performance has been studied and incoming packet will be discarded and denoted as max iii. analyzed by plotting different networking parameters in the X th. graph plotter. Minimum threshold (min th ): min th is another limit of the queue after which the incoming packets are dropped or marked with a The simulation topology with one bottleneck link is shown in fixed probability. iv. Loss rate (P a): P a is the probability with which packets are discarded. v. Maximum drop probability the Figure-1. (P ): It is peak value of P . The packets must be discarded if max a Table-1 gives parameters and its values used in the simulation. the P a value exceeds P max . vi. Weights (wq): wq is represents the avg queue size. International Science Community Association 2 Research Journal of Computer and Information Technology Sciences ___________________________________ ISSN 2320 – 6527 Vol.
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