This chapter introduces and analyses a class of non-linear congestion control algorithms called polynomial congestion control algorithms. These generalize the Additive Increase and Multiplicative Decrease (AIMD) algorithms used for the TCP connections. These algorithms provide additive increase using a polynomial of the inverse of the current window size and provide multiplicative decrease using the polynomial of the current window size. There are infinite numbers of TCP-compatible polynomial algorithms by assuming polynomial of different order. This chapter analyses the interaction between the two models (named as MIMD-Poly and PIPD-Poly) of these generalized algorithms, for the wired (with unicast and multicast) and wireless TCP networks. TCP compatibility of these algorithms is evaluated using the simulations of the implementations of the proposed two models. Simulations are done using ns2, a discrete event simulator. The model MIMD-Poly is proved to be TCP-compatible. The results of simulation are compared with that of the TCP variants such as TCP/Tahoe, TCP/Reno, TCP/New Reno, and TCP/Vegas. The Comparison shows that both algorithms perform better in terms of throughput.
TopIntroduction
During the last decade, computer networks have been growing very tremendously. Large number of computers gets connected to both private and public networks. In most of these networks the protocol stack used is TCP/IP. In spite of the rapid growth and explosive increase in traffic demand computer networks in general, Internet in particular is still working without collapse.
Also the growth of the Internet has sparked the demand of several applications, which require the stability of the Internet. For achieving such a success and to have the stability of Internet, mechanisms are developed to reduce transmission errors, to provide better bandwidth sharing of sources that use common bottleneck links, to reduce the Round Trip Time (RTT) and mainly to provide the congestion control by the transport layer protocol i.e. TCP (Transmission Control Protocol). TCP’s end-to-end congestion control mechanism reacts to packet loss by adjusting the number of outstanding unacknowledged data segments allowed in the network (Jacobson, 1988; Widmer et al., 2001). Such algorithms are implemented in its protocol, TCP. (Comer, 1991; Stevens, 1994; Allman & Paxson, 1999). In the existing algorithms, increasing the congestion window linearly with time increases the bandwidth of the TCP connection and when the congestion is detected, the window size is multiplicatively reduced by a factor of two (Yang & Lam, 2000).
TCP is not well suited for several emerging applications including streaming and real time audio and video because it increases end-to-end delay and delay variations (Jin et al., 2001).
This paper analyzes a new class of nonlinear congestion control algorithms for Internet Transport Protocols and applications. It seeks to develop a family of algorithms for applications such as Internet audio and video that does not react well to rate reductions, because the rate reduction technique used for these applications will result into the degradation in user-perceived quality (Allman & Paxson, 1999; Floyd & Fall, 1999). This analysis results into get good understanding of TCP-compatible congestion control algorithms by generalizing the Additive Increase and Multiplicative Decrease (AIMD) algorithms. The authors analyze the proposed algorithms in a simulated wired TCP network.
One of the current challenges of the Internet is to allow universal access to multimedia transmissions, even for receivers located within networks of different bandwidth and other characteristics. Multicast allows one single transmission to be delivered to a large number of receivers over a network (Seada et al., 2002). Congestion control is a major requirement for multicast to be deployed in the current Internet. This paper analyses the performance of the proposed congestion control algorithms in a wired network that employ multicast routing strategies.
With the proliferation of mobile computing devices, the demand for continuous network connectivity regardless of physical location has created greater interest in the use of mobile ad hoc networks (Sundaresan et al., 2003; Holland & Vaidya, 1999). This paper also analyze the performance of the proposed algorithms in Mobile Ad hoc Networks that uses TCP and compares the performance of the two proposed models with the standard AIMD algorithms implemented for TCP networks.
In all the simulations, the proposed two models are named as MIMD-Poly and PIPD-Poly. They are compared with the TCP variants such as TCP/Tahoe (called as TCP), TCP/Reno, TCP/NewReno, TCP/Vegas and the comparisons are simulated in ns2, the discrete event driven simulator that is used by most of the network researchers.