Conclusion

In this paper, we have presented a novel congestion avoidance mechanism for the Internet called Network Border Patrol. Unlike existing Internet congestion control approaches, which rely solely on end-to-end control, NBP is able to prevent congestion collapse from undelivered packets. It does this by ensuring at the border of the network that each flow's packets do not enter the network faster than they are able to leave it. NBP requires no modifications to core routers nor to end systems. Only edge routers are enhanced so that they can perform the requisite per-flow monitoring, per-flow rate control and feedback exchange operations.

Extensive simulation results provided in this paper show that NBP successfully prevents congestion collapse from undelivered packets. They also show that, while NBP is unable to eliminate unfairness on its own, it is able to achieve approximate global max-min fairness for competing network flows when combined with a fair queueing mechanism such as WFQ. Furthermore, NBP, when combined with CSFQ, approximates global max-min fairness in a completely core-stateless fashion.

As in any feedback-based traffic control mechanism, stability is an important performance concern in NBP. Using techniques described in [16], we plan as part of our future work to perform an analytical study of NBP's stability and convergence toward max-min fairness. Preliminary results already suggest that NBP benefits greatly from its use of explicit rate feedback, which prevents rate over-corrections in response to indications of network congestion.