35154579
Incorporating priority scheme in IPv6 over ATM networks
An effective approach to support multiple QoS classes in IPv6 running over ATM networks is implemented by mapping the priority field of IPv6 into the ATM format. Such a scheme might not be necessary for simple congestion control in a network of equal capacity links, however, it might be important for multicasting to destinations reachable through a very diverse capacity network. When network congestion occurs, the cell loss requirements for different services can be satisfied by selectively discarding low priority cells. As the multi-priority scheme used in IPv6 is a ''differentiated service'' mechanism to enhance the QoS by best effort, its performance is certainly affected by the background traffic when these multi-priority traffic are multiplexed at the ATM level. This paper focuses on the performance with multi-priority scheme under different traffic conditions to determine the loss characteristics. The expected results are how QoS is affected and how priority can be given for more important traffic in the case of congested network.
34513226
Incorporating priority scheme in IPv6 over ATM networks
An effective method to support multiple QoS classes in IPv6 over ATM networks is implemented by mapping of the priority field in IPv6 to the ATM cell. Such a scheme might not be necessary for simple congestion control in a network of equal capacity links; however, it might be important for multicasting to destinations reachable through a very diverse capacity network. When network congestion occurs, the cell loss requirements for different services can be satisfied by selectively discarding low priority cells. The results obtained show how the QoS can be affected by this field and how priority can be given for more important traffic in times of network congestion.
46136838
IPv6 traffic with multi-class QoS in VPN
Abstract This paper focuses on the modeling and performance analysis for IPv6 traffic with multi-class QoS in virtual private networks (VPNs). The multi-class QoS is implemented on differentiated service basis using priority scheme of 4 bits defined in the packet header of IPv6. A VPN-enabled IP router is modeled as a tandem queuing system in which each output link consists of two parallel priority output queues. The high-priority queue is used to carry the delay sensitive traffic while the low-priority queue is used to carry the delay insensitive traffic. On the other hand, multiple thresholds are implemented in each queue, respectively, for packet loss priority control. The performance analysis is done using fluid flow techniques. The numerical results obtained from the analysis show that the differentiated service based on the priority schemes defined in IPv6 is able to effectively satisfy the multi-class QoS requirement for supporting multimedia services in VPN. The performance trade-off between the delay sensitive traffic and delay insensitive traffic in terms of traffic throughput, packet loss probability and end-to-end delay in VPN networks is presented.
205935860
An ATM cross-connecting node using optical CDMA
An asynchronous transfer mode (ATM) cross-connecting node is proposed based on direct sequence optical code division multiple access (DS-OCDMA). No buffering is necessary to facilitate switching because code conversion is instead emulating the switching function. The switch is also capable of limited dynamic bandwidth allocation. It is free from timing jitters and switching delay is significantly reduced. The switch provides a new approach to asynchronous cross-connection in the ATM core network, locally or over a wider area. The performance with the new proposed switch is evaluated using prime and modified prime OCDMA codes.
10620171
Characterization of palmprints by wavelet signatures via directional context modeling
The palmprint is one of the most reliable physiological characteristics that can be used to distinguish between individuals. Current palmprint-based systems are more user friendly, more cost effective, and require fewer data signatures than traditional fingerprint-based identification systems. The principal lines and wrinkles captured in a low-resolution palmprint image provide more than enough information to uniquely identify an individual. This paper presents a palmprint identification scheme that characterizes a palmprint using a set of statistical signatures. The palmprint is first transformed into the wavelet domain, and the directional context of each wavelet subband is defined and computed in order to collect the predominant coefficients of its principal lines and wrinkles. A set of statistical signatures, which includes gravity center, density, spatial dispersivity and energy, is then defined to characterize the palmprint with the selected directional context values. A classification and identification scheme based on these signatures is subsequently developed. This scheme exploits the features of principal lines and prominent wrinkles sufficiently and achieves satisfactory results. Compared with the line-segments-matching or interesting-points-matching based palmprint verification schemes, the proposed scheme uses a much smaller amount of data signatures. It also provides a convenient classification strategy and more accurate identification.
6908840
Vigilante: end-to-end containment of internet worms
Worm containment must be automatic because worms can spread too fast for humans to respond. Recent work has proposed network-level techniques to automate worm containment; these techniques have limitations because there is no information about the vulnerabilities exploited by worms at the network level. We propose Vigilante, a new end-to-end approach to contain worms automatically that addresses these limitations. Vigilante relies on collaborative worm detection at end hosts, but does not require hosts to trust each other. Hosts run instrumented software to detect worms and broadcast self-certifying alerts (SCAs) upon worm detection. SCAs are proofs of vulnerability that can be inexpensively verified by any vulnerable host. When hosts receive an SCA, they generate filters that block infection by analysing the SCA-guided execution of the vulnerable software. We show that Vigilante can automatically contain fast-spreading worms that exploit unknown vulnerabilities without blocking innocuous traffic.
627898
Fault-tolerant data delivery for multicast overlay networks
Overlay networks represent an emerging technology for rapid deployment of novel network services and applications. However, since public overlay networks are built out of loosely coupled end-hosts, individual nodes are less trustworthy than Internet routers in carrying out the data forwarding function. Here we describe a set of mechanisms designed to detect and repair errors in the data stream. Utilizing the highly redundant connectivity in overlay networks, our design splits each data stream to multiple sub-streams which are delivered over disjoint paths. Each sub-stream carries additional information that enables receivers to detect damaged or lost packets. Furthermore, each node can verify the validity of data by periodically exchanging Bloom filters, the digests of recently received packets, with other nodes in the overlay. We have evaluated our design through both simulations and experiments over a network testbed. The results show that most nodes can effectively detect corrupted data streams even in the presence of multiple tampering nodes.
18465833
Contract-based mutation for testing components
Testing plays an important role in the maintenance of component based software development. Test adequacy for component testing is one of the hardest issues for component testing. To tackle this problem, it is a natural idea to apply mutation testing, which is a fault-based testing method used for measuring test adequacy, for component contracts, whose aim is to improve the testability of the component. Though powerful, mutation testing is usually very computation-expensive, as many mutants need to be produced and executed in mutation testing. In this paper, we propose a contract-based mutation technique for testing components. Based on the discordance between contracts and specification, our approach employs a set of high level contract mutation operators. The experimental results show that these operators can greatly reduce the number of mutants compared with traditional mutation operators. At the same time, the contract-based mutation using our contract mutation operators can provide almost the same ability as that of using traditional mutation operators. Moreover, effective test suite can be produced to reduce the maintenance effort.
14677925
Universal IP multicast delivery
A ubiquitous and efficient multicast data delivery service is essential to the success of large-scale group communication applications. The original IP multicast design is to enhance network routers with multicast capability [S. Deering, D. Cheriton, Multicast routing in datagram internetworks and extended LANs, ACM Transactions on Computer Systems 8(2) (1990) 85-110]. This approach can achieve great transmission efficiency and performance but also poses a critical dependency on universal deployment. A different approach, overlay multicast, moves multicast functionality to end hosts, thereby removing the dependency on router deployment, albeit at the cost of noticeable performance penalty compared to IP multicast. In this paper we present the Universal Multicast (UM) framework, along with a set of mechanisms and protocols, to provide ubiquitous multicast delivery service on the Internet. Our design can fully utilize native IP multicast wherever it is available, and automatically build unicast tunnels to connect IP Multicast "islands" to form an overall multicast overlay. The UM design consists of three major components: an overlay multicast protocol (HMTP) for inter-island routing, an intra-island multicast management protocol (HGMP) to glue overlay multicast and native IP multicast together, and a daemon program to implement the functionality at hosts. In addition to performance evaluation through simulations, we have also implemented parts of the UM framework. Our prototype implementation has been used to broadcast several workshops and the ACM SIGCOMM 2004 conference live on the Internet. We present some statistics collected during the live broadcast and describe mechanisms we adopted to support end hosts behind Network Address Translation (NAT) gateways and firewalls.