21 research outputs found

    BloomFlow: OpenFlow extensions for memory efficient, scalable multicast with Multi-Stage bloom filters

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    In-packet bloom filter based multicast is a family of techniques that have been recently proposed to address scalability issues in IP multicast. The main problem motivating these techniques is that network forwarding elements supporting traditional IP multicast store group specific forwarding state for every multicast tree traversing the element, resulting in poor memory scalability in networks with many active groups. Techniques in this family address this problem by encoding multicast routing information into in-packet bloom filters, which are memory efficient, probabilistic data structures for representing set membership. However, in existing approaches the probabilistic nature of bloom filters results in false-positive packet delivery, thereby introducing forwarding anomalies, unnecessary bandwidth utilization, and violations of security policies. In this work we contribute BloomFlow, a novel approach to bloom filter based multicast in SDN that achieves substantial forwarding state reduction while eliminating false positive packet delivery. The BloomFlow approach compensates for the stochastic uncertainty associated with bloom filters by incorporating the SDN network controller’s knowledge of the network topology and traffic workload into the generation of variable length and false-positive-free bloom filters. We further contribute a set of extensions to the OpenFlow protocol that demonstrates how our approach can be integrated into OpenFlow enabled networks with minimal modifications to switch hardware. We implement a working system prototype by extending the Stanford OpenFlow 1.0 Reference Switch and the POX SDN controller. We evaluate our approach through both flow level simulation, and packet level network emulation with Mininet and real media streams. We demonstrate that multicast forwarding using BloomFlow can achieve significant reductions in memory requirements due to network forwarding state (up to a ∼ 79% reduction in realistic WAN topologies under heavy multicast workloads). We find that this forwarding state reduction can be achieved with minimal bandwidth utilization overhead (averaging under ∼ 1%), and that our approach successfully meets time constraints required for deployment in a real-time SDN controller

    OPTIMAL CONTROL OF ARRIVALS AT A BLOCKING NODE.

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    Two communication traffic streams with Poisson statistics arrive at a network node. These are to be transmitted across a channel with a total bandwidth capacity of C frequency slots. Messages not accepted at the node are assumed to be lost. Under the assumption of exponential service time distributions, the authors study the problem of dynamic allocation of available channel bandwidth among the two traffic types to minimize a weighted sum of blocking probabilities. Modeling the system as a two-dimensional Markov chain, they show by an application of dynamic programming principles that the optimal policy is characterized by a set of two switching curves

    Jointly optimal admission and routing controls at a network node

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    We consider the problem of jointly optimal admission and routing at a data network node. Specifically, a message arriving at the buffer of a node in a data network is to be transmitted over one of two channels with different transmission times. Under suitably chosen criteria, two decisions have to be made: Whether or not to admit an incoming message into the buffer, and under what conditions should the slower channel be utilized. A discounted infinite-horizon cost as well as an average cost are considered. These costs consist of a linear combination of the blocking probability and the queueing delay at the buffer. The optimal admission and routing strategies are shown to be characterized almost completely by means of “switching curves”

    Optimal Admission Control of Two Traffic Types at a Circuit- Switched Network Node

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    Two communication traffic streams with Poisson statistics arrive at a network node on separate routes. These streams are to be forwarded to their destinations via a common trunk. The two links leading to the common trunk have capacities C1 and C2 bandwidth units, respectively, while the capacity of the common trunk is C bandwidth units, where C < C1 + C2. Calls of either traffic type that are not admitted at the node are assumed to be discarded. An admitted call of either type will occupy, for an exponentially distributed random time, one bandwidth unit on its forwarding link as well as on the common trunk. Our objective is to determine a scheme for the optimal dynamic allocation of available bandwidth among the two traffic streams so as to minimize a weighted blocking cost. The problem is formulated as a Markov decision process. By using dynamic programming principles, the optimal admission policy is shown to be of the "bang-bang" type, characterized by appropriate "switching curves". The case of a general circuit-switched network, as well as numerical examples, are also presented

    OPTIMAL SERVICE ALLOCATION AMONG TWO HETEROGENEOUS TRAFFIC TYPES WITH NO QUEUEING.

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    Two communication traffic streams with Poisson statistics arrive at a network node. These are to be transmitted across a channel with a total bandwidth capacity of C slots. Messages not accepted at the node are assumed to be lost. Under the assumptions of exponential service time distributions, the problem of dynamic allocation of available channel bandwidth among the two traffic types is studied in order to minimize a weighted sum of blocking probabilities. Modeling the system as a two-dimensional Markov chain is studied to minimize a weighted sum of blocking probabilities. Modeling the system as a two-dimensional Markov chain, it is shown by an application of dynamic programming principles that the optimal policy has the form of a 'switching curve'

    DiffServ model with backpressure for CDMA2000

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    Joint access control and user removal in a CDMA cell with multimedia traffic

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    This paper deals with the problem of admission control when different traffic media with different quality of service requirements (QOS) are sharing a CDMA (Code Division Multiple Access) channel. We propose an adaptive access control method based on the equivalent bandwidth theory and cell load measurements. Our algorithm allows efficient integration of speech and low bit rate video in an outdoor CDMA cellular network in the presence of interference from neighboring cells

    Effect of channel variation in IP/cdma2000 interconnection performance

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    In order to support high data rate requirements and effectively manage the scarce wireless resources, additional band-width channels are allocated and taken away from mobile stations in 3G wireless data networks quite frequently. A TCP sender connected to the mobile, on seeing ACKs coming at a faster pace after additional bandwidth allocation, turns overtly optimistic and injects data into the network in a more bursty manner that might be excessive for an intermediate router, thereby leading to loss of multiple packets and subsequent prolonged recovery and periods of underutilization. In this work, we characterize this problem using an analytical model for losses based on continuous flow approximation as well as an extensive simulation setup. We also illustrate how bandwidth oscillations create more severe congestion than an increase in number of users to the extent that even RED algorithm is unable to check the sharp growth of queues. As a result, multiple packets are lost in a droptail fashion. We further demonstrate the dependence of congestion due to bandwidth allocation on the time during which mobiles' rates are increased and observe the degradation in performance for typical load scenarios

    Two level access control strategy for multimedia CDMA

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    In this paper we propose a new technique for access control in an outdoor CDMA cell supporting multimedia traffic. The proposed scheme controls the flow of the traffic at both packet and call level. Delay scheduling at packet level is employed to minimize the variance of intra-cell interference while a call admission control based on a modified equivalent bandwidth technique exploits the minimized interference and reduces the call blocking probability. It is shown that the proposed scheme allows efficient integration of voice and low bit rate video in a CDMA cell with imperfect power control
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