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This paper investigates and compares the performance of the popular VoIP codecs G.711, G.723.1 and G.729A over an IP network based on SIP architecture, using RTP as a transport protocol. This is based on different simulations in order to evaluate the performance of each codec and to find the optimal codec. For this objective this paper analyzes Quality of service (QoS) parameters, principally delay,...
The goal of this work is to characterize scientific data transfers and to determine the suitability of dynamic virtual circuit service for these transfers instead of the currently used IP-routed service. Specifically, logs collected by servers executing a commonly used scientific data transfer application, GridFTP, are obtained from three US super-computing/scientific research centers, NERSC, SLAC,...
Replication techniques that tolerate byzantine failures have been applied in distributed computing to cope with hostile environments in which system components may fail due to malicious or natural causes (e.g., intrusions). From the seminal work of Lamport, Pease and Shostak on Byzantine Generals, in 1982, Castro and Liskov proposed in 1999 a successful solution, named PBFT, which overcomes performance...
In this paper, we present analytical study of routing overhead of reactive routing protocols for Wireless Multihop Networks (WMhNs). To accomplish the framework of generalized routing overhead, we choose Ad-Hoc on Demand Distance Vector (AODV), Dynamic Source Routing (DSR) and Dynamic MANET on Demand (DYMO). Considering basic themes of these protocols, we enhance the generalized network models by...
In recent years, BitTorrent traffic accounts for a substantial percentage of Internet traffic in the world. However, the current BitTorrent protocols disregards traffic cost at the underlying network and generate a large amount of inter-AS traffic. As a result, BitTorrent peers may suffer from slow download of files due to long delays. Moreover, ISPs may limit BitTorrent traffic to reduce inter-AS...
In distributed systems, a group of multiple processes are required to cooperate with each other to achieve some objectives. In this paper, we consider a distributed system where there is o centralized coordinator. Each member process is peer, i.e. each peer has to autonomously make a decision by itself through communicating with other peers in a group. Each peer sends a message to every peer and every...
In this paper, we propose a distributed fault localization protocol for localizing multi-link failures in EPC global networks. the protocol is based on a parallel limited-perimeter vector matching (P-LVM) mechanism, which restricts fault localization within a smaller perimeter area and can thus significantly reduce fault localization time. by performing a fault localization process sequentially in...
Airborne networks often use frequency hopping to be jam resistant. Because users are highly mobile and can have large propagation delays, otherwise orthogonal frequency hopping patterns appear asynchronous, and hop-by-hop collisions will occur. We compare the achievable throughput and delay of scheduling schemes versus random access schemes in this context via modeling and simulation. Because collisions...
In this paper, we proposed an efficient FSN (first station number) assignment scheme to mitigate urgent message transmission delay in multi-hop MIL-STD-188-220D w/Change 1 networks. In the standard, the FSN is incremented constantly and designates the index of a station that is to have the first network access opportunity at the next network access period. When a station transmits its message to stations...
Satellite systems can be fruitfully utilized to provide connectivity to terrestrial sensor networks to exploit large-scale monitoring applications based on IP protocol. Sensor traffic patterns are very different from those occurring with current Internet applications, so that performance evaluation requires some specific investigation with the aim to draw the main requirements to achieve target Quality...
For the low delay requirements of Ad Hoc networks in high traffic-load, it mentioned an improved algorithm named Slotted ALOHA based on Multichannel Statistics (SAMS) . Compared to the widely used protocol of ALOHA, Slotted ALOHA, CSMA and TDMA, the result of SAMS simulation proved it can maintain very low delay of ensuring the high-priority data send successfully in high traffic-load.
This contribution focuses on securing end-to-end unicast communications in heterogeneous wireless sensor networks comprising satellite links, while maintaining effective network performance. The proposed protocol extends the LOCKSAT key management procedure, and is able to guarantee a frequent key renewal while overcoming limitations of each subnetwork (e.g., sensor and satellite). The effectiveness...
The quality-of-service (QoS) metrics in a wireless sensor network (WSN) of multiple sensor types depend on the performance of the network protocol layers, motivating a comprehensive cross-layer design approach to optimize QoS. Advances in energy-harvesting techniques enable increases in WSN lifetime by prolonging operation of the wireless nodes. While the primary objective of energy harvesting is...
We consider the problem of synchronizing prioritized data on two distinct hosts in disruption-tolerant networks (DTNs). To this effect, we propose and analyze a new interactive protocol for priority-oriented synchronization, called P-CPI, that is especially efficient in terms of bandwidth usage. This middleware protocol has features that are particularly useful for DTN routing in constrained or tactical...
The Internet Protocol Multimedia Subsystem (IMS) has been recognized as a common signaling architecture for providing next generation multimedia services. In order to enhance perceived service quality regardless of access network and device, IMS supports Quality of Service (QoS) negotiation and signaling. The IMS procedures used for that purpose are based on Session Initiation Protocol (SIP). Therefore,...
The Internet has now become such an important infrastructure that is capable of sending information within a very short time and easy to access. It is considered as public networks that provide affordable WAN services to most customers. Applications such as video conferencing, file transfer protocol and VoIP are the example of typical network applications supported by the Internet Protocol. Various...
Due to the US Government's cancellation of the Transformational Satellite Communications (TSAT) program, Internet Protocol (IP) networking using Military Satellite Communications (MILSATCOM) is not currently planned. In order to support military IP based communications over MILSATCOM systems; affordable, effective and efficient solutions must be developed. An alternate near-term MILSATCOM networking...
In this paper, we propose relay transmission protocol based on SoQ(Satisfaction of QoS) for QoS enhancement and analyze the performance of the proposed method in Wireless USB Networks. In the proposed protocol, Wireless USB host executes the Satisfaction of QoS (SoQ) time slot allocation algorithm. And, in order to give devices with scarce resource another chance to improve QoS, the proposed relay...
This paper proposes message scheduling on dedicated time slot of ISA100.11a to satisfy real time property. In this paper, a superframe is designed to accommodate periodic real time (PRT) message, aperiodic real time (alarm) message, and non real time (NRT) message. To do so, a superframe is divided into dedicated time slot (DTS) which is used to send PRT message and shared time slot (STS) which is...
Due to the lack of end-to-end connectivity between mobile nodes, delay tolerant networks (DTNs) exploit the opportunistic forwarding mechanism. This mechanism requires nodes to forward messages in a cooperative way. Nevertheless, nodes may exhibit selfish behavior, in particular when they are constrained with respect to the battery energy, computational power, and/or storage space. In this paper,...
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