832 research outputs found
Throughput and fairness of multiple TCP connections in wireless networks
TCP suffers from poor throughput performance in wireless networks. Furthermore, when multiple TCP connections compete at the base station, link errors and congestion lead to serious unfairness among the connections. Although the issue of TCP performance in wireless networks has attracted significant attention, most reports focus only on TCP throughput and assume that there is only a single connection in a congestion-free network. This paper studies the throughput and fairness of popular improvement mechanisms (the Snoop [8] and ELN [5]) and TCP variants with multiple TCP connections. Simulation results show that the improvement mechanisms under investigation are effective to improve TCP throughput in a wireless network. However, they cannot provide fairness among multiple TCP connections. From the studies presented, it is concluded that mechanisms to enhance TCP fairness are needed in wireless network
Network coding meets TCP
We propose a mechanism that incorporates network coding into TCP with only
minor changes to the protocol stack, thereby allowing incremental deployment.
In our scheme, the source transmits random linear combinations of packets
currently in the congestion window. At the heart of our scheme is a new
interpretation of ACKs - the sink acknowledges every degree of freedom (i.e., a
linear combination that reveals one unit of new information) even if it does
not reveal an original packet immediately. Such ACKs enable a TCP-like
sliding-window approach to network coding. Our scheme has the nice property
that packet losses are essentially masked from the congestion control
algorithm. Our algorithm therefore reacts to packet drops in a smooth manner,
resulting in a novel and effective approach for congestion control over
networks involving lossy links such as wireless links. Our experiments show
that our algorithm achieves higher throughput compared to TCP in the presence
of lossy wireless links. We also establish the soundness and fairness
properties of our algorithm.Comment: 9 pages, 9 figures, submitted to IEEE INFOCOM 200
SatERN: a PEP-less solution for satellite communications
In networks with very large delay like satellite IPbased
networks, standard TCP is unable to correctly grab the
available resources. To overcome this problem, Performance Enhancing Proxies (PEPs), which break the end-to-end connection and simulate a receiver close enough to the sender, can be placed before the links with large delay. Although splitting PEPs does not modify the transport protocol at the end nodes, they prevent the use of security protocols such as IPsec. In this paper, we propose solutions to replace the use of PEPs named SatERN. This
proposal, based on Explicit Rate Notification (ERN) protocols over IP, does not split connections and is compliant with IP-in-IP tunneling solutions. Finally, we show that the SatERN solution achieves high satellite link utilization and fairness of the satellite traffic
Bandwidth Sharing Scheme of End-to-End Congestion Control Protocols
In a general network, it is not easy to find according to which
criterion the available bandwidth would be shared between
competing flows. In this paper, we propose a technique to find the
bandwidth sharing scheme of end-to-end congestion control
protocols. This technique divides the analysis work into two
separate steps. In the first step, one should find the rate
function, which expresses the relation between the throughput and
the congestion measure. In the second step, the utility function
can be obtained from the rate function
Link Buffer Sizing: a New Look at the Old Problem
In this paper, we revisit the question of how much buffer an IP router should allocate for its output link. For a long time, the intuitive answer of setting the buffer size to the bitrate-delay product has been widely regarded as reasonable. Recent studies of interaction between queueing at IP routers and TCP congestion control proposed alternative answers. First, we expose and explain contradictions between existing guidelines for link buffer sizing. Then, we argue that the problem of link buffer sizing needs a different formulation. In particular, the chosen buffer size should accommodate not only common versions of TCP but also UDP trafïŹc. Besides, our new formulation of the problem contains an explicit constraint of not engaging IP routers in any additional signaling. We conclude the paper by outlining a promising direction for solving the reformulated problem
Selecting the Buffer Size for an IP Network Link
In this paper, we revisit the problem of selecting the buffer size for an IP network link. After a comprehensive overview of issues relevant to the link buffer sizing, we examine usefulness of existing guidelines for choosing the buffer size. Our analysis shows that the existing recommendations not only are difïŹcult to implement in the context of IP networks but also can severely hurt interactive distributed applications. Then, we argue that the networking research community should change its way of thinking about the link buffer sizing problem: the focus should shift from optimizing performance for applications of a particular type to maximizing diversity of application types that IP networks can support effectively. To achieve this new objective, we propose using small buffers for IP network links
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