Abstract. Wireless wide-area networks (WWANs) are characterized by very low and variable bandwidths, very high and variable delays, significant non-congestion related losses, asymmetric uplink and downlink channels, and occasional blackouts. Additionally, the majority of the latency in a WWAN connection is incurred over the wireless link. Under such operating conditions, most contemporary wireless TCP algorithms do not perform very well. In this paper, we present WTCP, a reliable transport protocol that addresses rate control and reliability over commercial WWAN networks such as CDPD. WTCP is rate-based, uses only end-to-end mechanisms, performs rate control at the receiver, and uses inter-packet delays as the primary metric for rate control. We have implemented and evaluated WTCP over the CDPD network, and also simulated it in the ns-2 simulator. Our results indicate that WTCP can improve on the performance of comparable algorithms such as TCP-NewReno, TCP-Vegas, and Snoop-TCP by between 20 % to 200 % for typical operating conditions.

Due to the availability of a wide variety of wireless access technologies, a mobile host can potentially have subscriptions and access to more than one wireless network at a given time. In this paper, we consider such a multi-homed mobile host, and address the problem of achieving bandwidth aggregation by striping data across the multiple interfaces of the mobile host. We show that both link layer striping approaches and application layer techniques that stripe data across multiple TCP sockets do not achieve the optimal bandwidth aggregation due to a variety of factors specific to wireless networks. We propose an end-to-end transport layer approach called pTCP that effectively performs bandwidth aggregation on multi-homed mobile hosts. We show through simulations that pTCP achieves the desired goals under a variety of network conditions.

Current TCP protocols have lower throughput performance in satellite networks mainly due to the effects of long propagation delays and high link error rates. In this paper, a new congestion control scheme called TCP-Peach is introduced for satellite networks. TCP-Peach is composed of two new algorithms, namely Sudden Start and Rapid Recovery, as well as the two traditional TCP algorithms, Congestion Avoidance and Fast Retransmit. The new algorithms are based on the novel concept of using dummy segments to probe the availability of network resources without carrying any new information to the sender. Dummy segments are treated as low-priority segments and accordingly they do not effect the delivery of actual data traffic. Simulation experiments show that TCP-Peach outperforms other TCP schemes for satellite networks in terms of goodput. It also provides a fair share of network resources.

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Wireless links have intrinsic characteristics that affect the performance of transport protocols; these include variable bandwidth, corruption, channel allocation delays, and asymmetry. In this paper we review simulation models for cellular, WLAN and satellite links used in the design of transport protocols, and consider the interplay between wireless links and transport. We argue that the design and evaluation of transport protocols can be improved by providing easily available models of wireless links that strike a balance between realism, generality, and detail.

Understanding the performance of the Internet’s Transmission Control Protocol (TCP) is important because it is the dominant protocol used in the Internet today. Various testing methods exist to evaluate TCP performance, however all have pitfalls that need to be understood prior to obtaining useful results. Simulating TCP is difficult because of the wide range of variables, environments, and implementations available. Testing TCP modifications in the global Internet may not be the answer either: testing new protocols on real networks endangers other people’s traffic and, if not done correctly, may also yield inaccurate or misleading results. In order for TCP research to be independently evaluated in the Internet research community there is a set of questions that researchers should try to answer. This paper attempts to list some of those questions and make recommendations as to how TCP testing can be structured to provide useful answers. 1

In traditional operating systems, modifying the network protocol code is a tedious and error-prone task, largely because the networking stack resides in the kernel. For this reason, among others, many have proposed moving the networking stack to user-level. Unfortunately, implementations of this design have never entered widespread use due to the impractical requirements they place on the user: either the kernel or applications must be modified; or code cannot be moved seamlessly between the user-level and kernel stacks. In this paper, we present Alpine, a user-level networking infrastructure free from these drawbacks. Alpine supports a FreeBSD networking stack on top of a Unix operating system. It is freely available as source code. In this paper, we discuss the challenges we faced in virtualizing the FreeBSD networking stack without compromising on kernel, networking stack, and application compatibility. We then show how Alpine is effective at easing the burden of debugging and testing protocol modifications or new network protocols. In our experience, Alpine can reduce the overhead of modifying a protocol from hours to minutes. 1

FEC is widely used to improve the quality of noisy transmission media as wireless links. This improvement is of importance for a transport protocol as TCP which uses the loss of packets as an indication of network congestion. FEC shields TCP from losses not caused by congestion but it consumes some bandwidth that could be used by TCP. We study in this paper the tradeoff between the bandwidth consumed by FEC and that gained by TCP.

The developments in the space technologies are enabling the realization of deep space scientific missions such as Mars exploration. Inter

Abstract—Space exploration missions are crucial for acquisition of information about space and the universe. The entire success of a mission is directly related to the satisfaction of its communications needs. For this goal, the challenges posed by the InterPlaNetary (IPN) Internet need to be addressed. Current transmission control protocols (TCPs) have very poor performance in the IPN Internet, which is characterized by extremely high propagation delays, link errors, asymmetrical bandwidth, and blackouts. The window-based congestion control, which injects a new packet into the network upon an ACK reception, is responsible for such performance degradation due to high propagation delay. Slow start algorithms of the existing TCPs further contribute to the performance degradation by wasting long time periods to reach the actual data rate. Moreover, wireless link errors amplify the problem by misleading the TCP source