Differentiated Bandwidth Allocation with TCP Protection in Core Routers

Differentiated Services (DiffServ) networks categorize routers into edge routers and core routers. In core routers, one of the technological challenges is how to implement differentiated bandwidth allocation and TCP protection together with low complexity. We present an Active Queue Management (AQM) scheme called CHOKeW. A method is borrowed from a previous scheme, CHOKe, which draws a packet at random from the buffer, compares it with the arriving packet, and drops both if they are from the same flow. 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. With respect to the number of flows, both the memory-requirement complexity and the per-packet-processing complexity for CHOKeW is O(1). An analytical model and multiple simulations are used to explain and evaluate CHOKeW. We show that CHOKeW is able to (1) support differentiated bandwidth allocation; (2) provide the flows in the same priority with better fairness than other 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.