This paper examines congestion control issues for
TCP flows that require in-network processing on the fly in
network elements such as gateways, proxies, firewalls and even
routers. Applications of these flows are increasingly abundant in
the future as the Internet evolves. Since these flows require use of
CPUs in network elements, both bandwidth and CPU resources
can be a bottleneck and thus congestion control must deal
with “congestion” on both of these resources. In this paper, we
show that conventional TCP/AQM schemes can significantly lose
throughput and suffer harmful unfairness in this environment,
particularly when CPU cycles become more scarce (which is likely
the trend given the recent explosive growth rate of bandwidth). As
a solution to this problem, we establish a notion of dual-resource
proportional fairness and propose an AQM scheme, called Dual-
Resource Queue (DRQ), that can closely approximate proportional
fairness for TCP Reno sources with in-network processing
requirements. DRQ is scalable because it does not maintain perflow
states while minimizing communication among different
resource queues, and is also incrementally deployable because
of no required change in TCP stacks. The simulation study
shows that DRQ approximates proportional fairness without
much implementation cost and even an incremental deployment
of DRQ at the edge of the Internet improves the fairness and
throughput of these TCP flows. Our work is at its early stage and
might lead to an interesting development in congestion control
research.