TCP tunnel is a technology that aggregates and transfers packets sent between end hosts as a single TCP connection. By using a TCP tunnel, the fairness among aggregated flows can be improved and several protocols can be transparently transmitted through a firewall. Currently, many applications such as SSH, VTun, and HTun use a TCP tunnel. However, since most applications running on end hosts generally use TCP, two TCP congestion controls (i.e., end-to-end TCP and tunnel TCP) operate simultaneously and interfere each other. Under certain conditions, it has been known that using a TCP tunnel severely degrades the end-to-end TCP performance. Namely, it has known that using a TCP tunnel drastically degrades the end-to-end TCP throughput for some time, which is called TCP meltdown problem. On the contrary, under other conditions, it has been known that using a TCP tunnel significantly improves the end-to-end TCP performance. However, it is still an open issue -how, when, and why is a TCP tunnel malicious for end-to-end TCP performance? In this paper, we therefore investigate effect of TCP tunnel on end-to-end TCP performance using simulation experiments. Specifically, we quantitatively reveal effects of several factors (e.g., the propagation delay, usage of SACK option, TCP socket buffer size, and sender buffer size of TCP tunnel) on performance of end-to-end TCP and tunnel TCP.
In recent years, IP-based virtual private networks (IP-VPNs), which provide a virtual privately owned network over an IP network, have attracted attention. With existing IP-VPNs, however, there is a serious problem that fairness among IP-VPN customers is not satisfied. In this paper, we first discuss design objectives of a control mechanism for achieving fair IP-VPN services: achieving inter-VPN fairness, achieving intra-VPN fairness, easy deployment into existing IP networks, and achieving a high scalability. We then propose an IP-VPN fairness control called I2FVC (Inter-and Intra-VPN Fairness Control) for realizing a fair IP-VPN service in a scalable way. The core of I2VFC is an AIMD (Additive Increase and Multiplicative Decrease) window flow control operating among IP-VPN service provider's edge routers. I2VFC has the advantage that an IP-VPN service provider can arbitrarly specify inter-VPN fairness criteria by utilizing analytic results of AIMD window flow control. Moreover, I2VFC can be easily deployed into existing IP networks by simply modifying edge routers. Through several simulation experiments, we demonstrate that I2VFC realizes both inter-VPN fairness and intra-VPN fairness with extremely high accuracy.
We propose terabit-class super-networking technologies, designed to improve the scalability, reliability and performance of optical IP networks. Our technologies comprise both intralayer and interlayer traffic engineering technologies. The intralayer technologies include an optical path protection scheme, an electrical load-balancing scheme and a distributed content-caching scheme. These provide an effective and economical way of improving performance and reliability. The interlayer technologies include both traffic-driven and application-driven optical cut-through control schemes and a policy control scheme. These provide an effective and economical way of improving scalability and performance. The feasibility of our technologies has been verified by means of experiments using prototype systems shown in Fig. 1. The results of the experiments are as follows: O-SP network Optical domain E-SP network NCS Optical domain Management network IP router Site (CDN, LAN)
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