Active Queue Management in a QOS Enabled Network

IP provides only best efforts service but multimedia and real time applications require Quality of Service (QOS). Queue management algorithms which operate at the core of the network and that choose which packet has to be dropped, in case of buffer overflow or when the buffer size exceeds certain threshold make a significant contribution to QOS. DropTail is the traditional queue management algorithm, which drops packets when queue is full. This has two major problems, Lockout and Global synchronization that make it unsuitable for a QOS enabled network. RED is a proactive approach to congestion control. By providing advanced warning of incipient congestion, RED enables end nodes to respond to congestion before router buffer overflows and hence ensure improved performance.This paper does the performance comparison of Drop Tail and RED and does an extensive study of RED. We examined the impact of both the Queue disciplines on TCP traffic. Performance difference is observed at higher levels of congestion. We measured the average queuing delay of Drop Tail and RED. RED by maintaining average queue size small tries to minimize the delay, which makes it suitable for delay sensitive applications. We then compared RED Byte and Packet modes of operation. The effect of RED's ability to mark packets instead of Asst. Prof in CSE, JNTU College of Engg, Anantapur, Andra Pradesh. E-mail: pcreddy1@rediffmail.com Assoc. Prof and Head of ECE, JNTU College of Engg. Anantapur, Andra Pradesh. E-mail: pcreddy21@rediffmail.comdropping them called Explicit Congestion Notification is also studied. The simulation is performed using NS2 and graphs are drawn using Xgraph.