waashk/dblp huggingface dataset:
performance of packet video with combined error recovery and concealment. in this paper we analyze the performance of a video transport across an atm network that uses both retransmission and concealment to recover from errors due to cell loss resulting from congestion. we limit the number of retransmission attempts to one. if a frame is still in error after one retransmission attempt, the remaining errors are concealed. we obtain analytic expressions for the peak signal to noise ratio (psnr) with combined retransmission and concealment. the analysis shows that significant improvement in the signal to noise ratio of the reconstructed picture can be achieved if retransmission and concealment are used together.
multi-class connection admission control policy for high speed atm switches. broadband networks based on atm have to support multiple classes of services with widely different traffic characteristics and quality of services. in this paper, we propose and develop a multi-class connection admission control (cac) policy that supports cell loss and delay requirements. in this model-based cac, the source traffic is described in terms of the usage parameter control (upc) parameters. through careful analysis and approximations, we derive simple closed-form formulas to calculate the bandwidth required to meet guarantees on quality of service (qos). while being robust, the cac achieves a high level of resource utilization and can be easily implemented for real-time admission control.
dynamic bandwidth allocation in broadband isdn using a multilevel optimal control approach. this paper presents a novel scheme for the dynamic allocation of bandwidth at the virtual path level in b-isdns. a fluid flow model is developed to describe the time varying mean behaviour of a virtual path and serves as a state variable model. a multilevel optimal control theoretic approach is used in conjunction with the state model to derive a coordinated decentralised algorithm for virtual path bandwidth allocation. the performance of the proposed scheme is evaluated using simulation.
the rate mismatch problem in heterogeneous abr flow control. because the atm forum does not standardize the abr flow control algorithm that an atm switch should run, some atm networks are likely to contain switches that run different abr flow control algorithms. even if all the switches within a ``cloud'' of switches use the same algorithm, individual clouds (each with its own algorithm) will be interconnected by virtual circuits. virtual circuits which traverse multiple clouds will therefore be controlled by two different flow control algorithms concurrently. in this paper we explore some of the ramifications of mixing different flow control algorithms in the same atm network. we identify the rate mismatch problem, which arises when a nonbottleneck switch (that uses one algorithm) interferes with the control of the bottleneck switch (that uses another algorithm). we formulate a hypothesis that states the conditions that lead to the rate mismatch problem. these conditions identify a specific class of problematic topologies. we validate the hypothesis formally and prove that rate mismatch causes unfairness. using four different algorithms, in combinations of two at a time, we illustrate the interoperability of abr flow control algorithms.
multiwavelength optical networks with limited wavelength conversion. this paper proposes optical wavelength division multiplexed (wdm) networks with limited wavelength conversion that can efficiently support lightpaths (connections) between nodes. each lightpath follows a route in the network and must be assigned a channel along each link in its route. the load lambdamax of a set of lightpath requests is the maximum over all links of the number of lightpaths that use the link. at least lambdamax wavelengths will be needed to assign channels to the lightpaths. if the network has full wavelength conversion capabilities then lambdamax wavelengths are sufficient to perform the channel assignment.we propose ring networks with fixed wavelength conversion capability within the nodes that can support all lightpath request sets with load lambdamax at most w-1, where w is the number of wavelengths in each link. we also propose ring networks with selective pairwise wavelength conversion capability within the nodes that can support all lightpath request sets with load lambdamax at most w. we also propose a star network with fixed wavelength conversion capability at its hub node that can support all lightpath request sets with load lambdamax at most w. we extend this result to tree networks and networks with arbitrary topologies. these results show that significant improvements in traffic-carrying capacity can be obtained in wdm networks by providing very limited wavelength conversion capability within the network.
on optimal call admission control in cellular networks. two important quality-of-service (qos) measures for current cellular networks are the fraction of new and handoff ``calls'''' that are blocked due to unavailability of ``channels'''' (radio and/or computing resources). based on these qos measures, we consider optimal admission control policies for three problems: minimizing a linear objective function of the new and handoff call blocking probabilities (minobj), minimizing the new call blocking probability with a hard constraint on the handoff call blocking probability (minblock) and minimizing the number of channels with hard constraints on both the blocking probabilities (minc). we show that the well-known {\it guard channel policy is optimal for the minobj problem}, while a new {\it fractional guard channel policy is optimal for the minblock and minc problems}. the guard channel policy reserves a set of channels for handoff calls while the fractional guard channel policy effectively reserves a non-integral number of guard channels for handoff calls by rejecting new calls with some probability that depends on the current channel occupancy. it is also shown that the fractional policy results in significant savings (20-50\%) in the new call blocking probability for the minblock problem and provides some, though small, gains over the integral guard channel policy for the minc problem. we see that the fractional guard channel policy offers more flexibility than the guard channel policy in the sense of a richer set of parameters but the algorithms developed in the paper for determining the optimal parameter settings for the fractional policy are computationally inexpensive. finally, we briefly explore the possibility of exploiting the combination of these features of the fractional guard channel policy and its concomitant algorithms for real-time control of cellular networks.
average waiting time profiles of uniform dqdb model. the distributed queue dual bus (dqdb) system consists of a linear arrangement of n nodes that communicate with each other using two contra-flowing buses; the nodes use an extremely simple protocol to send messages on these buses. this simple, but elegant, system has been found to be very challenging to analyze. we consider a simple and uniform abstraction of this model to highlight the fairness issues in terms of average waiting time. we introduce a new approximation method to analyze the performance of dqdb system in terms of the average waiting time of a node expressed as a function of its position. our approach abstracts the intimate relationship between the load of the system and its fairness characteristics, and explains all basic behavior profiles of dqdb observed in previous simulation. for the uniform dqdb with equal distance between adjacent nodes, we show that the system operates under three basic behavior profiles and a finite number of their combinations that depend on the load of the network. consequently, the system is not fair at any load in terms of the average waiting times. in the vicinity of a critical load of 1 - 4/n, the uniform network runs into a state akin to chaos, where its behavior fluctuates from one extreme to the other with a load variation of 2/n. our analysis is supported by simulation results. we also show that the main theme of the analysis carries over to the general (non-uniform) dqdb; by suitably choosing the inter-node distances, the dqdb can be made fair around some loads, but such system will become unfair as the load changes.
optimal configuration of ospf aggregates. open shortest path first (ospf) is a popular protocol for routing within an autonomous system (as) domain. in order to scale for large networks containing hundreds and thousands of subnets, ospf supports a two-level hierarchical routing scheme through the use of ospf areas. subnet addresses within an area are aggregated, and this aggregation is a crucial requirement for scaling ospf to large as domains, as it results in significant reductions in routing table sizes, smaller link-state databases, and less network traffic to synchronize the router link-state databases. on the other hand, address aggregation also implies loss of information about the length of the shortest path to each subnet, which in turn, can lead to suboptimal routing.in this paper, we address the important practical problem of configuring ospf aggregates to minimize the error in ospf shortest-path computations due to subnet aggregation. we first develop an optimal dynamic programming algorithm that, given an upper bound k on the number of aggregates to be advertised and a weight assignment function for the aggregates, computes the k aggregates that result in the minimum cumulative error in the shortest-path computations for all source-destination subnet pairs. subsequently, we tackle the problem of assigning weights to ospf aggregates such that the cumulative error in the computed shortest paths is minimized. we demonstrate that, while for certain special cases (e.g., unweighted cumulative error) efficient optimal algorithms for the weight assignment problem can be devised, the general problem itself is np-hard. consequently, we have to rely on search heuristics to solve the weight assignment problem. to the best of our knowledge, our work is the first to address the algorithmic issues underlying the configuration of ospf aggregates and to propose efficient configuration algorithms that are provably optimal for many practical scenarios.
source time scale and optimal buffer/bandwidth trade-off for regulated traffic in an atm node. in this paper, we study the problem of resource allocation and control for an atm node with regulated traffic. both guaranteed lossless service and statistical service with small loss probability are considered. we investigate the relationship between source characteristics and the buffer/bandwidth trade-off under both services.our contributions are the following. for guaranteed lossless service, we find that the optimal resource allocation scheme suggests a time scale separation of sources sharing an atm node with finite bandwidth and buffer space, with the optimal buffer/bandwidth trade-off is determined by the sources' time scale. for statistical service with a small loss probability, we present a new approach for estimating the loss probability in a shared buffer multiplexor with the so called ``extremal'' on-off, periodic sources. under this approach, the optimal resource allocation for statistical service is achieved by maximizing both the benefits of buffering sharing and bandwidth sharing. the optimal buffer/bandwidth trade-off is again determined by time scale separation.besides their obvious application to resource allocation and call admission control, our results have many other implications in network design and control such as network dimensioning and traffic shaping.
the linearity of low frequency traffic flow: an intrinsic i/o property in queueing systems. consider a class of queueing systems which can be modeled by a finite quasi-birth-death (qbd) process. in this paper we develop a powerful computational technique for spectral analyses (i.e. second-order statistics) of output, queue and loss. emphasis is placed on output power spectrum and input-output coherence function in response to various input power spectral properties and system parameters. the coherence function is defined to measure linear relationship between input and output processes. a key technical contribution of this paper is the exploration of linearity of low frequency traffic flow. through the evaluation of the coherence function, one can identify a so-called nonlinear break frequency, /spl omega//sub b/, under which the low frequency traffic stay intact via a queueing system. such a low frequency i/o linearity plays an important role in characterizing the output process, which may form a partial input to other "downstream" queues of the network. after all, it is the "upstream" output low frequency characteristics that will have most impact on the "downstream" queueing performance. our study further indicates that the link capacity required by an input process is essentially characterized by its maximum input rate filtered at /spl omega//sub b/.
on optimal placement of erasure nodes on a dual bus network. erasure node placement on the distributed and queue dual bus (dqdb) network is a well investigated problem. for general traffic conditions, achieving maximum throughput by placing a minimum number of erasure nodes optimally is known as the optimal placement of erasure nodes. to date, all the solutions proposed are either of exponential time complexity of generate suboptimal placement or work under impractical assumptions. the authors present a polynomial time algorithm that obtains optimal placement of erasure nodes for general traffic conditions. they derive a closed form expression for maximum achievable throughput and show that several bounds proposed in the literature can be obtained as special cases from the method.
implementation of a secure bridge in an ethernet environment. the implementation of a security system that caters to the needs of an operating network, the upc net, is presented. the security services that this system offers are confidentiality and authentication (origin authentication and data integrity) of data transmitted on the main segment of an extended ethernet network. the system has been designed to specifically function in the extended ethernet network of the polytechnic university of catalonia. the security system has the following characteristics: it provides cryptographic security services, it does not interfere with the operation of unprotected systems, and it supports transparent operations for protected systems
integrated network management: technologies and implementation experience. an analysis of the requirements and key enabling technologies for the development of intelligent and integrated enterprise network management systems is presented. in particular, the analysis demonstrates the advantages of exploiting the synergy of object-oriented and knowledge-based technologies, together with the emerging network management standard protocols between conformant management entities. the experience with applying these concepts to the evolution of the management system for large multivendor data communication networks is outlined
bandwidth allocation for broadband multichannel systems. the authors examine an optimal bandwidth allocation scheme for multichannel switching systems to switch trunk groups. this multichannel switching system features a simple architecture, high throughput, high channel utilization, and other properties such as preserving packet sequence, being robust to unbalanced input traffic loads, providing fair access to network transmission resources, and fast packet processing via a pipeline structure. numerical results show that the multichannel system can achieve a throughput of 91% per channel for a trunk group of 32 channels while also providing very low average cell delay performance in the presence of correlated inputs
design and analysis of a credit-based controller for congestion control in b-isdn/atm networks. a credit-based controller (cbc), which has a provision for cell tagging, is proposed for usage parameter control (upc). similar in concept to the leaky bucket, the cbc has a credit counter and a data buffer. credits are accumulated at a rate initiated from the network (equivalent to the sustainable cell rate), and depleted at a rate pertaining to the network traffic load. a source has the prerogative whether or not to send its cells as tagged cells when the credit level is nonpositive. the queueing behavior of the cbc fed by a marcov modulated source, is analyzed using a stochastic fluid flow model. it is shown that the performance of the cbc can be altered by tuning the weighting parameter within the cbc. also, adjustments can be made to balance the ratio of tagged and untagged cells sent into the network.
information exchange protocol: a new approch for future network management. the paper proposes a new approach to classify the network management information formally and the authors intend to support the description of the network states and events. the classification concept described is slightly different from the approaches of cmip (common management information protocol). the authors apply the situation classification capability extended from those found in description logic, in order to organize the state and event for network management in hierarchical structure. this approach is an extension of current cmip approach with combined classification facility of relationship, concept and objects.
a comparison of application-level and router-assisted hierarchical schemes for reliable multicast. one approach to achieving scalability in reliable multicast is to use a hierarchy. a hierarchy can be established at the application level, or by using router-assist. with router-assist we have more fine-grain control over the placement of error-recovery functionality, therefore, a hierarchy produced by assistance from the routers is expected to have better performance. in this paper, we test this hypothesis by comparing two schemes, one that uses an application-level hierarchy (alh) and another that uses router-assisted hierarchy (rah). contrary to our expectations, we find that the qualitative performance of alh is comparable to rah. we do not model the overhead of creating the hierarchy nor the cost of adding router-assist to the network. therefore, our conclusions inform rather than close the debate of which approach is better.
a scalable architecture for fair leaky-bucket shaping. this paper presents a shaper architecture that scales to a large number of connections with diverse burstiness and bandwidth parameters. the architecture arbitrates fairly between connections with conforming cells by carefully integrating leaky-bucket traffic shaping with rate-based scheduling algorithms. through a careful combination of per-connection queueing and approximate sorting, the shaper performs a small, bounded number of operations in response to each arrival and departure, independent of the number of connections and cells. to handle a wider range of rate parameters, a hierarchical arbitration scheme can reduce the implementation overheads and the interference between competing connections. simulation experiments demonstrate that the architecture limits shaping delay and traffic distortions, even under heavy congestion.
admission control for hard real-time connections in atm lans. the cac algorithm must efficiently determine if a new connection can be admitted by verifying that its qos requirements can be met without violating those of pr eviously admitted connections. in hard real-time systems, the qos requirements are specified in terms of end-to-end deadlines and no cell loss due to buffer ov erflow. a cac algorithm must account for interdependencies among connections ca used by statistical multiplexing of cells in atm networks. furthermore, arbitra ry topology of the network may lead to cyclic dependencies among various connect ions. we present an efficient cac algorithm that addresses the above issues. t he algorithm uses a traffic descriptor called the maximum traffic rate function to effectively compute bounds on end-to-end delays of connections and buffer req uirements within the network. our work differs from most previous work in that it does not require traffic restoration inside the network.
a unified framework and algorithm for (t/f/c)dma channel assignment in wireless networks. channel assignment problems in the time, frequency and code domains have thus far been studied separately. exploiting the similarity of ``constraints'' that characterize assignments within and across these domains, we introduce the first unified framework for the study of assignment problems. our framework identifies eleven atomic constraints underlying most current and potential assignment problems, and characterizes a problem as a combination of these constraints. based on this framework, we present a unified algorithm for efficient (t/f/c)dma channel assignments to nodes or to inter-nodal links in a (multihop) wireless network. the algorithm is parametrized to allow for tradeoff-selectable use as three different variants called rand, mnf, and pmnf. using theoretical analysis, we show that the worst-case performance guarantee of pmnf is an order of magnitude better than that of the traditional rand and mnf for most networks. we also experimentally study the relative performance for one node and one link assignment problem. we observe that pmnf performs the best, and that a larger fraction of unidirectional links degrades the performance in general.
mtcp: scalable tcp-like congestion control for reliable multicast. we present mtcp, a congestion control scheme for large-scale reliable multicast. congestion control for reliable multicast is important, because of its wide applications in multimedia and collaborative computing, yet non-trivial, because of the potentially large number of receivers involved. many schemes have been proposed to handle the recovery of lost packets in a scalable manner, but there is little work on the design and implementation of congestion control schemes for reliable multicast. we propose new techniques that can effectively handle instances of congestion occurring simultaneously at various parts of a multicast tree.our protocol incorporates several novel features: (1) hierarchical congestion status reports that distribute the load of processing feedback from all receivers across the multicast group, (2) the relative time delay concept which overcomes the difficulty of estimating round-trip times in tree-based multicast environments, (3) window-based control that prevents the sender from transmitting faster than packets leave the bottleneck link on the multicast path through which the sender's traffic flows, (4) a retransmission window that regulates the flow of repair packets to prevent local recovery from causing congestion, and (5) a selective acknowledgment scheme that prevents independent (i.e., non-congestion-related) packet loss from reducing the sender's transmission rate. we have implemented mtcp both on udp in sunos 5.6 and on the simulator ns, and we have conducted extensive internet experiments and simulation to test the scalability and inter-fairness properties of the protocol. the encouraging results we have obtained support our confidence that tcp-like congestion control for large-scale reliable multicast is within our grasp.