Explicit Congestion Notification (ECN) protocol provides the
mechanism for using Congestion Experienced (CE) code point in the packet header
as an indication of congestion, instead of relying solely on packet drops. ECN
can be used as a congestion indication policy of Active Queue Management (AQM)
mechanisms e.g. Random Early Detection (RED), Dynamic RED (DRED). This thesis
proposes "ECN over RED", "MECN over RED", and "ECN
over DRED" protocols. We analyze and evaluate these protocols (with
extensive performance characteristics: queue size, bottleneck link utilization,
throughput, goodput, queue size, delay, fairness) in
homogeneous and heterogeneous networks using OPNET Modeler
simulation tool.
Based on the simulation results, two enhancements to the basic "ECN over RED" protocol - "Fair ECN (FECN) over RED" and "Mark First FECN (MFFECN) over RED" are proposed and analyzed. "FECN over RED" provides higher bandwidth to connections with longer Round Trip Time (RTT) when competing with lower RTT connections. This results in better fairness in a heterogeneous network. "MFFECN over RED" proposes a mark-front strategy instead of the mark-tail strategy of the standard "ECN over RED" in order to speed up the congestion notifications to the sender. These protocols have been evaluated against "ECN over RED" using the OPNET Modeler simulation tool.