The evolution of congestion control in TCP/IP: from reactive windows to preventive rate control
Jim C. Martin, Arne A. Nilsson · NCSU Libraries Repository (North Carolina State University Libraries) · 1997
In a packet switched network, multiple sessions or users compete for network resources.Network resources include bandwidth (i.e., the transmission capacity of a link in the network), a router's switching capacity and a router's buffer capacity.If demand for a resource exceeds the capacity, congestion occurs.Symptoms of network congestion include increased packet delays or packet loss (from buffer overflow).Congestion control is the aspect of a networking protocol that defines how the network deals with congestion.The congestion control schemes employed by the TCP/IP protocol have been widely studied.The mechanisms continue to be enhanced as TCP/IP evolves to meet new and more demanding requirements.It has been debated over the past decade as to whether window or rate control is more effective at controlling congestion.Recent work suggests that adding burst control to TCP provides relatively minor performance improvements.Furthermore it has been shown (through simulation) that the current TCP protocol is not able to efficiently utilize reserved bandwidth over an RSVP controlled-load connection.However, a set of enhancements have been proposed, the most significant being rate control, that address the limitations of TCP in an Integrated Services environment.Taking this one step further, we suggest that the performance of a rate-based version of TCP in an Integrated Services environment can be further improved with an additional end-to-end preventive congestion control scheme.This paper is organized as follows.First, we provide a detailed discussion of congestion control in packet switched networks.Essentially we provide a framework that is used to describe and differentiate specific congestion control schemes throughout the paper.Next we cover TCP/IP congestion control, surveying the relevant research.Lastly we overview the Integrated Services Architecture focusing on congestion control and TCP performance issues.