Probabilistic testing of OSI protocols

Protocols are large and complex software systems. Complete conformance testing of an implementation against its standard may not be feasible in terms of the resources available. This paper discusses a new approach, the P-method, to the testing of meaningful subsets of communication protocols for an asynchronous model of communication. The approach is based on the probabilistic verification of protocols, which is carried out on the more probable part of the protocol first. The technique can be used for generating probabilistic test sequences for the conformance testing of communication protocols to standards. The proposed method yields meaningful protocol test sequences which test the most probable behaviors of a protocol when the testing of the complete protocol is not feasible. Probabilistic test sequences can be categorized into different classes. The higher the class a probabilistic test sequence is in, the larger the extent of the protocol it covers, and the better is the fault coverage. If the class of a test sequence is high enough, its fault coverage is comparable to the fault coverage of test sequences generated by other methods. Results from a study of the P-method, using alternating bit protocol (ABP) and a subset of NBS TP4 as examples, support the claims above. It can also be shown that if errors are introduced only to the more probable part of the protocol, the fault coverage of P-method is also comparable to other methods     

Active networks as a developing and testing environment for network protocols

Active Networks is a modern network approach in which pieces of code can be downloaded and executed on network devices, affecting in this way their behavior. This approach alters the philosophy of a computer network, makes it resemble to a distributed system and affects not only network protocols, services or applications, but also high-level mechanisms and procedures. One of the affected procedures is the development and testing of new protocols. By exploiting active network properties the development of a network protocol can be simplified to software development. Expensive and time-consuming hardware implementations are avoided, while the code can be developed, shared and tested by individual researchers. Testing can be performed on actual conditions instead of using inaccurate simulations. Early implementations of the protocol, which can be modified easily while the protocol evolves, can be used to obtain useful feedback. This paper describes our experiences of developing and testing of some of theietf cops family protocols in an Active Environment.     

网络入侵中未知协议识别单元的设计与测试

为了提高复杂环境下的网络安全性,设计并实现了一种网络入侵中未知协议识别单元。系统通过网络入侵检测模块对网络入侵进行检测并过滤,使得未知协议识别单元的设计不受网络入侵的干扰。利用流量采集模块对网络节点的网络流量进行采集,为后续阶段提供完整的网络数据包以及充分的数据分析样本,将采集的网络数据包以指针的形式返回,发送至流量调度模块。通过流量调度模块将网络数据包的源IP地址作为调度参数,依据用户自定义调度算法将网络数据包传输至指定识别模块,实现整个网络入侵中未知协议识别单元的负载均衡。利用规则匹配模块将从流量调度模块接收到的信息和协议特征库进行匹配,从而实现未知协议的识别。软件设计过程中,对网络入侵中未知协议识别单元进行了详细分析,并给出了网络入侵中未知协议识别的程序代码。仿真实验结果验证了该系统的可行性和实用性。     

On certificate-based security protocols for wireless mobilecommunication systems

Mutual authentication and session key exchange protocols based on certificates for the wireless mobile communication/computing system are proposed. First, two improved versions for the conventional certificate-based systems are proposed, and an offline authentication mechanism based on the dynamic certificate is introduced. Then, an end-to-end internetwork-authenticated session key exchange protocol, which preserves a private communication between two mobile users, is finally proposed. In designing the security protocols proposed, the low computational power of the mobile stations and the low bandwidth of the wireless networks are considered     

On the implant communication and MAC protocols for WBAN

Recent advances in micro‐electro‐mechanical systems, wireless communication, low‐power intelligent sensors, and semiconductor technologies have allowed the realization of a wireless body area network (WBAN). A WBAN provides unobtrusive health monitoring for a long period of time with real‐time updates to the physician. It is widely used for ubiquitous health care, entertainment, and military applications. The implantable and wearable medical devices have several critical requirements such as power consumption, data rate, size, and low‐power medium access control (MAC) protocols. This article consists of two parts: body implant communication, which is concerned with the communication to and from a human body using radio frequency (RF) technology, and WBAN MAC protocols, which presents several low‐power MAC protocols for a WBAN with useful guidelines including a case study of IEEE 802.15.4, PB‐TDMA, and SMAC protocols. In body implant communication, the in‐body RF performance is affected considerably by the implant's depth and different polarization combinations inside the human body as well as by the muscle and fat. We observe best performance at a depth of 3 to 5 cm and not close to the human skin. Furthermore, the study of low‐power MAC protocols highlights the most important aspects of developing a novel low‐power and reliable MAC protocol for a WBAN. Copyright © 2010 John Wiley & Sons, Ltd.     

On composability of localization protocols for wireless sensor networks

Realistic, complex outdoor environments pose significant challenges for node localization in wireless sensor networks. In spite of the fact that many elegant and clever solutions have been proposed, no robust localization system has emerged. This status quo is because existing solutions work well for single sets of assumptions that, however, do not always hold in complex environments. In this article we review the state of the art for node localization in wireless sensor networks and show how localization protocol composability has the potential to provide the robust solution that is needed. By composing localization protocols in a hierarchy and allowing the execution of multiple localization schemes, robust solutions against any single protocol failure can be built.     

Thinking about thinking aloud: a comparison of two verbal protocols for usability testing

We report on an exploratory experimental comparison of two different thinking aloud approaches in a usability test that focused on navigation problems in a highly nonstandard Web site. One approach is a rigid application of Ericsson and Simon's (for original paper see Protocol Analysis: Verbal Reports as Data, MIT Press (1993)) procedure. The other is derived from Boren and Ramey's (for original paper see ibid., vol. 43, no. 3, p. 261-278 (2000)) proposal based on speech communication. The latter approach differs from the former in that the experimenter has more room for acknowledging (mm-hmm) contributions from subjects and has the possibility of asking for clarifications and offering encouragement. Comparing the verbal reports obtained with these two methods, we find that the process of thinking aloud while carrying out tasks is not affected by the type of approach that was used. The task performance does differ. More tasks were completed in the B and R condition, and subjects were less lost. Nevertheless, subjects' evaluations of the Web site quality did not differ, nor did the number of different navigation problems that were detected.     

Policy hierarchies for distributed systems management

Distributed system management, involves monitoring the activity of a system, making management decisions and performing control actions to modify the behavior of the system. Most of the research on management has concentrated on management mechanisms related to network management or operating systems. However, in order to automate the management of very large distributed systems, it is necessary to be able to represent and manipulate management policy within the system. These objectives are typically set out in the form of general policies which require detailed interpretation by the system managers. The paper explores the refinement of general high-level policies into a number of more specific policies to form a policy hierarchy in which each policy in the hierarchy represents, to its maker, his plans to meet his objectives and, to its subject, the objectives which he must plan to meet. Management action policies are introduced, and the distinction between imperatival and authority policies is made. The relationship of hierarchies of imperatival policies to responsibility, and to authority policies, is discussed. An outline approach to the provision of automated support for the analysis of policy hierarchies is provided, by means of a more formal definition of policy hierarchy refinement relationships in Prolog     

On designing MAC protocols for wireless networks using directional antennas

We investigate the possibility of using directional antennas for medium access control in wireless ad hoc networks. Previous research in ad hoc networks typically assumes the use of omnidirectional antennas at all nodes. With omnidirectional antennas, while two nodes are communicating using a given channel, MAC protocols such as IEEE 802.11 require all other nodes in the vicinity to remain silent. With directional antennas, two pairs of nodes located in each other's vicinity may potentially communicate simultaneously, increasing spatial reuse of the wireless channel. Range extension due to higher gain of directional antennas can also be useful in discovering fewer hop routes. However, new problems arise when using directional beams that simple modifications to 802.11 may not be able to mitigate. This paper identifies these problems and evaluates the tradeoffs associated with them. We also design a directional MAC protocol (MMAC) that uses multihop RTSs to establish links between distant nodes and then transmits CTS, DATA, and ACK over a single hop. While MMAC does not address all the problems identified with directional communication, it is an attempt to exploit the primary benefits of beamforming in the presence of some of these problems. Results show that MMAC can perform better than IEEE 802.11, although we find that the performance is dependent on the topology and flow patterns in the system.     

On chip novel video streaming system for bi-network multicasting protocols

In the past three decades, tremendous Ethernet-related research has been done, which has led to today's ubiquitous Ethernet technology. On the other hand, with the emergence of new network needs, a new protocol, the IEEE 1394 standard serial bus (or Firewire) was introduced. Firewire is suitable for high-quality audio/video applications which do not perform well in the best-effort-based Ethernet technology. However, since Firewire is a serial bus, it has harsh cable length limitations as compared to Ethernet capabilities.In this paper, we present a novel on-chip system that receives Firewire video and transmits it in multicast mode using Ethernet protocol. A major advantage of this novel system is to utilize the existing Ethernet infrastructure to extend the range of Firewire video streaming to reach remote nodes and make it even accessible to nodes with a single Ethernet interface. This will have tremendous impact on Firewire applications such as deploying Firewire cameras in big-scale security-sensitive buildings or industrial facilities with image-based remote quality control.This novel chip utilizes the concept of Ethernet multicasting transmission mode for video streaming. The proposed chip design converts the IEEE 1394 isochronous traffic to the Ethernet multicast frame format via two off-chip asynchronous write and read buffers.The goal of this research is to design an On Chip Novel Video Streaming System that avoids performance bottlenecks in the software protocol conversion of these two important network protocols. The author decided to study these two networks because of their broad use and cable power provisioning capabilities. The novel system design is implemented using a customized field programmable gate array (FPGA), which enables the integration of various system components on one chip. The designed prototype is studied using both network monitoring tools and analytical techniques, to verify its function and compare it with the existing approaches.Performance measures show that the On Chip Novel Video Streaming System consumes less than 21 mW of power for 100 Mbps and 82 mW of power for 1 Gbps, and utilizes 57% of a Xilinx Spartan 2-100E-6FT256 FPGA resources. Hence, it is possible to incorporate further extensions. Experimental results show that 88% of the network utilization can be achieved, due to the use of the customized, FPGA-based design of bi-network traffic conversion.     

Analysis and testing of application layer protocols with anapplication to FTAM

An experience with formal specification, analysis, and testing of an application layer protocol is presented. The ISO file, transfer, access, and management (FTAM) protocol is chosen due to its potential for widespread use. The specification language used was the ISO standard Estelle. This tool generates control and dataflow graphs of the specification and derives unparameterized test sequences for each function identified by the user. The authors describe formal specification of application layer protocols in Estelle and translation of ASN.1 data definitions into Estelle data types. The test design tool is used to obtain functional decomposition of the control and dataflow graphs. This way unparameterized test sequences are obtained. These sequences lead to a complete test suite obtained by parameterization which must be the next step. Analysis of the control and dataflow graphs leads to the derivation of several properties that most of the application layer protocols must possess. The identified properties are shown to simplify the test design process     

On the scalability of data synchronization protocols for PDAs andmobile devices

Personal digital assistants and other mobile computing devices rely on synchronization protocols in order to maintain data consistency. These protocols operate in environments where network resources such as bandwidth, memory and processing power are limited. We examine a number of popular and representative synchronization protocols, such as Palm's HotSync, Pumatech's Intellisync and the industry-wide SyncML initiative. We investigate the scalability performance of these protocols as a function of data and network sizes and compare them to a novel synchronization approach, CPISync, which addresses some of their scalability concerns. The conclusions of this survey are intended to provide guidance for handling scalability issues in synchronizing data on large, heterogeneous, tetherless networks     

On transient behaviours of slotted CSMA protocols

CSMA protocols have been extensively studied under the assumption of an equilibrium condition. The results obtained in this manner provided useful insight for the development of packet radio and local area networks for the transmission of bursty data. The integration of isochronous and bursty traffic in the same network may, however, make the equilibrium assumption unrealistic, for example when fixed-length frames are defined, only a portion of which is devoted to the transmission of bursty data according to a CSMA protocol. In such cases, it is necessary to study the protocol behaviours in fixed-length time segments. This paper presents a technique for the analysis of slotted CSMA protocols in such an environment. Definitions for the transient throughput and transient average packet delay are introduced, and closed form expressions are derived for non-persistent and 1-persistent CSMA and CSMA/CD protocols with arbitrary distribution of the packet length. Numerical results help in the visualization of some interesting phenomena, peculiar to the CSMA operations in finite-length intervals.     

On testing for improper error detection codes

A family of tests for improper codes is given. These tests can be used in cases where the complete weight distribution of the code is unknown. It was found that knowledge of the number of minimum weight codewords can be used to greatly increase the effectiveness of the asymptotic Varshamov-Gilbert test. Further improvement is possible as more is known about the number of other weight codewords     

On the reliability of ad hoc routing protocols for loss-and-delay sensitive applications

In this paper, we analyze the packet delivery reliability of ad hoc routing protocols for loss-and-delay sensitive applications. Since a typical flooding-based route discovery used in ad hoc routing protocols – DSR for instance – can only discover node-disjoint paths. In this context, we first show that the reliability function of such a multipath system is concave with respect to the total number of paths. Therefore, maximum steady-state reliability may be attained by routing each packet through a small set of node-disjoint paths. Subsequently, we prove that a partially-disjoint path is more reliable than a node-disjoint path. Hence, high reliability and significant energy savings may be achieved by routing a packet through fewer partially-disjoint paths. Based on these findings, we suggest modifications to flooding-based route discovery procedure to discover partially-disjoint paths. We complement our theoretical outcomes through extensive simulations. Finally, we analyze the reliability of beacon-based routing protocols and derive an upper bound on the number of hops at which a beacon should be placed to satisfy a given packet reliability constraint.     

On testing communications networks

A preliminary study of the concepts and methodology needed to build an intelligent system for fault detection and isolation in digital, analog, and fiber-optical networks is presented. The network domain is used because it is both tractable and of great pragmatic significance. Current views on these issues are summarized and an overview of future development guidelines is provided. Expert Tester (ExT), a production knowledge-based diagnostic expert system, is used to illustrate an implementation of the theory and the concepts that are described     

Conformance testing of protocols specified as communicating finitestate machines-a guided random walk based approach

We present a new approach for conformance testing of protocols specified as a collection of communicating finite state machines (FSMs). Our approach uses a guided random walk procedure. This procedure attempts to cover all transitions in the component FSMs. We also introduce the concept of observers that check some aspect of protocol behavior. We present the result of applying our method to two example protocols: full-duplex alternating bit protocol and the ATM-adaptation-layer-convergence protocol. Applying our procedure to the ATM adaptation layer, 99% of component FSMs edges can be covered in a test with 11692 input steps. Previous approaches cannot do conformance test generation for standard protocols (such as asynchronous transfer mode (ATM) adaptation layer) specified as a collection of communicating FSMs     

On the generation of minimal-length conformance tests forcommunication protocols

A technique for generating a test sequence for conformance testing of communication protocols is presented. This approach shows that it is possible to generate optimal-length test sequences which include multiple unique input/output (UIO) sequences and overlapping under certain conditions. In the absence of the above-mentioned conditions, a heuristic technique is used to obtain suboptimal solutions which show significant improvement over optimal solutions without overlapping. The technique is illustrated by the example of the NBS Class 4 Transport Protocol (TP4). The computational complexity of the algorithm is compared with that of previous techniques. A brief discussion of bounds on test sequence length is presented, and the results are compared with these bounds     

On optimum selection relaying protocols in cooperative wireless networks

In this letter, the outage probabilities of selection relaying protocols are analyzed and compared for cooperative wireless networks. It is assumed that both source and relay use equal allocated time in transmission. Depending on the quality of the source-relay channel, the relay may choose either Decode-and-Forward (DF), Amplify-and-Forward (AF), or Direct-Transmission (DT) to forward signals. It turns out that in terms of outage probability, two selection relaying schemes are better than others: selecting between DF and AF protocols (DF-AF) or selecting between DF and DT protocols (DF-DT). It is shown that with an equal power allocation, both of the DF-AF and DF-DT selection relaying protocols have the same asymptotic outage probability. However, with an optimum power allocation strategy, the DF-AF selection scheme is in general better than the DF-DT selection scheme. Note that the optimum power allocations depend on channel variances, not on instantaneous channel gains. When the quality of the relay-destination link is much better than that of the source-relay link, observed from simulation, the outage probability of the DF-AF selection protocol with its optimum power allocation is 1.5dB better than that of the DF-DT selection with its own optimum power allocation. Extensive simulations are presented to validate the analytical results.     

On the capacity of infinite population multiple access protocols

We present bounds on the maximum channel utilization (with finite average delay) of synchronous multiple access communications protocols serving an infinite population of homogeneous stations. Messages arrive to the system as a series of independent Bernoulli trials in discrete time, with probability p of an arrival at each arrival point (the Poisson limit is explicitly included) and are then randomly distributed among the stations. Pippenger showed that the channel utilization cannot exceedxi_{p}, wherexi_{l}=1andlim_{p rightarrow 0} xi_{p} approx 0.744. Using a "helpful genie" argument, we find the exact capacity for allp geq 0.568(where we find optimal protocols that obey first-come first-served); for smaller values of p, we present an improved upper bound that decreases monotonically toapprox 0.6731in the Poisson limit asp rightarrow 0.