19697806
Should Decision Trees be Learned using Rough Sets?
39032710
Refining decision tree classifiers using rough set tools
The proposed hybridized rough set framework is composed of traditional Rough Set (RS) approach and classical Decision Tree (DT) induction algorithm. RS helps to identify dominant attributes and DT algorithm results in simpler and generalized classifier. The implementation of the Hybridized Rough Set Framework is presented as the RDT algorithm. GA heuristics are used to generalize the RDT algorithm further. Experimental results obtained on applying the hybridized rough set framework and the related base algorithms on datasets belonging to the three categories are presented in this paper. Accuracy, complexity, number of rules and number of attributes in the induced classifier assess the performance of the candidate algorithms. The results indicate that the proposed framework is an effective model for classification.
38848848
Rough Set Based Decision Tree Model for Classification
Decision tree, a commonly used classification model, is constructed recursively following a top down approach (from the general concepts to particular examples) by repeatedly splitting the training data set. ID3 is a greedy algorithm that considers one attribute at a time for splitting at a node. In C4.5, all attributes, barring the nominal attributes used at the parent nodes, are retained for further computation. This leads to extra overheads of memory and computational efforts. Rough Set theory (RS) simplifies the search for dominant attributes in the information systems. In this paper, Rough set based Decision Tree (RDT) model combining the RS tools with classical DT capabilities, is proposed to address the issue of computational overheads. The experiments compare the performance of RDT with RS approach and ID3 algorithm. The performance of RDT over RS approach is observed better in accuracy and rule complexity while RDT and ID3 are comparable.
56733
Fairness for ABR multipoint-to-point connections
In multipoint-to-point connections, the traffic at the root is the combination of all traffic originating at the leaves. A crucial concern in the case of multiple senders is how to define fairness within a multicast group, and among groups and point-to-point connections. Fairness definition can be complicated since the multipoint connection can have the same identifier on each link, and senders might not be distinguishable in this case. Many rate allocation algorithms implicitly assume that there is only one sender in each VC, which does not hold for multipoint-to-point cases. We give various possibilities for defining fairness for multipoint connections, and show the tradeoffs involved. In addition, we show that ATM bandwidth allocation algorithms need to be adapted to give fair allocations for multipoint-to-point connections.
16881430
Multimedia Satellite Networks and TCP/IP Traffic Transport
Abstract To meet an increasing demand for multimedia services and electronic connectivity across the world, satellite networks will play an indispensable role in the deployment of global networks. A number of satellite communication systems have been proposed using geosynchronous (GEO) satellites, medium earth orbit (MEO) and low earth orbit (LEO) constellations operating in the Ka-band and above. At these frequencies, satellite networks are able to provide broadband services requiring wider bandwidth than the current services at C or Ku-band. Most of the next-generation broadband satellite systems will use ATM or "ATM-like" switching with onboard processing to provide full two-way services to and from earth stations. The new services gaining momentum include mobile services, private intranets, and high-data-rate internet access carried over integrated satellite-fiber networks. Several performance issues need to be addressed before a transport layer protocol like TCP can satisfactorily work over satellite ATM for large delay-bandwidth networks. The authors review the proposed satellite systems and discuss challenges such as traffic management and QoS requirements for broadband satellite ATM networks. The performance results of TCP enhancements for Unspecified Bit Rate over ATM (ATM-UBR+) for large bandwidth-delay environments with various end system policies and drop policies for several buffer sizes are presented.
357941
A comparison of hashing schemes for address lookup in computer networks
Using a trace of address references, the author compares the efficiency of several different hashing functions such as cyclic redundancy checking polynomials, Fletcher checksum, folding of address octets using the exclusive-OR operation, and bit extraction from the address. Guidelines are provided for determining the size of hash masks required to achieve a specified level of performance. >
52864471
A binary feedback scheme for congestion avoidance in computer networks
We propose a scheme for congestion avoidance in networks using a connectionless protocol at the network layer. The scheme uses a minimal amount of feedback from the network to the users, who adjust the amount of traffic allowed into the network. The routers in the network detect congestion and set a congestion-indication bit on packets flowing in the forward direction. The congestion indication is communicated back to the users through the transport-level acknowledgment. The scheme is distributed, adapts to the dynamic state of the network, converges to the optimal operating point, is quite simple to implement, and has low overhead. The scheme maintains fairness in service provided to multiple sources. This paper presents the scheme and the analysis that went into the choice of the various decision mechanisms. We also address the performance of the scheme under transient changes in the network and pathological overload conditions.
1255552
Design issues for providing minimum rate guarantees to the ATM unspecified bit rate service
We describe proposed enhancements to the ATM unspecified bit rate (UBR) service that guarantee a minimum rate at the frame level to the UBR VCs. These enhancements have been called guaranteed frame rate (GFR). In this paper, we discuss the motivation, design and implementation issues for GFR. We present the design of buffer management and tagging mechanisms to implement GFR. We study the effects of policing, per-VC buffer allocation, and per-VC queueing on providing GFR to TCP/IP traffic. We conclude that when the entire link capacity is allocate to GFR traffic, per-VC scheduling is necessary to provide minimum throughput guarantees to TCP traffic. We examine the role of frame tagging in the presence of scheduling and buffer management for providing minimum rate guarantees.