Differentiated Bandwidth Allocation with TCP Protection in Core Routers
Differentiated Services (DiffServ) networks have received wide attention for several years. They categorize routers into edge routers and core routers. In core routers, one of the technological challenges is to implement differentiated bandwidth allocation and TCP protection with low complexity, where conventional per-flow queueing is costly. In this paper, we present an Active Queue Management (AQM) scheme called CHOKeW, named after previous work CHOKe that is effective to protect TCP flows. A method is borrowed from CHOKe that draws a packet at random from the buffer, compares it with the arriving packet, and drops both if they are from the same flow ( we call this "matched drops"). CHOKeW enhances the drawing function by adjusting the maximum number of draws based on the priority of the new arrival and the current status of network congestion. The number of parameters that CHOKeW needs to maintain is determined by the number of priority levels being supported by the network, which usually has a small limited value. With respect to the number of flows (say N) going through the router in the core networks, both the memory-requirement complexity and the per-packet-processing complexity for CHOKeW is O(1), as compared to O(N) and usually greater than O(1), respectively, which has been seen in conventional per-flow schemes. In order to explain the features of CHOKeW, an analytical model is used, followed by running a series of simulations to evaluate the performance. We show that under a variety of congestion scenarios, CHOKeW is able to 1) support differentiated bandwidth allocation by affording a larger bandwidth share to higher priority flows, 2) provide the flows in the same priority with better fairness than conventional stateless AQM schemes such as RED and BLUE, 3) maintain high link utilization as well as short queue length, and 4) protect TCP flows by restricting the bandwidth share of high-speed unresponsive flows.
router network operations