Request For Comments Research Articles

Design and performance evaluation of a fuzzy based traffic conditioner for differentiated services

The current Internet can only provide the best-effort services. By growing the Internet and its applications, new services with different requirements are developed. The differentiated services (Diffserv) [S. Blake, M. Carlson, E. Davies, Z. Wang, W. Weiss, An Architecture for Differentiated Services, IETF RFC 2475, 1998; K. Nichols, V. Jacobson, L. Zhang, A Two-bit Differentiated Services Architecture for the Internet, IETF RFC 2638, July 1999; T. Li, Y. Rekhter, A Provider Architecture for Differentiated Services and Traffic Engineering (PASTE), IETF RFC 2430, October 1998] is a scalable model for providing end-to-end quality of services. A Diffserv router consists of different components including classifier, meter, marker, dropper, shaper and scheduler. In this paper, we use the benefits of the fuzzy logic controller to design a fuzzy based traffic conditioner for Internet differentiated services. Our proposed model consists of three major parts: a fuzzy meter/marker (FM), a fuzzy active queue management (FAQM) algorithm and a fuzzy scheduler (FS). The proposed FM used to measure and mark the input traffic is based on the single rate three colors meter (srTCM) mechanism [J. Heinane, et al., A Single Rate Three Color Marker, RFC 2697, September 1999]. The FM meters an IP packet stream and marks its packets GREEN, YELLOW, or RED. The proposed FAQM is a fuzzy implementation of the well-known BLUE active queue management (AQM) algorithm [W. Feng, D. Kandlur, D. Saha, K. Shin, BLUE: A New Class of Active Queue Management Algorithms U. Michigan CSE-TR-387-99, April 1999]. To achieve a good throughput and reasonable packet loss ratio, the proposed FAQM mechanism employs a fuzzy logic controller. The third part of the proposed fuzzy traffic conditioner is FS. It is based on the traditional weighted fair queue (WFQ) mechanism [A. Demers, S. Keshav, S. Shenker, Analysis and simulation of a fair queueing algorithm, in: SIGCOMM Symposium on Communications Architectures and Protocols, Austin, Texas, September 1989, pp. 1–12] that tunes the weight of each queue by a fuzzy logic controller. To evaluate the performance of the proposed model, we developed a software in C++ environment to simulate it. Different network topologies with different traffic parameters were performed. The simulation results easily helped us to judge the merit of the proposed FM, FAQM and FS because of their remarkable performance over the traditional non-fuzzy mechanisms.

OLSR performance measurement in a military mobile ad hoc network

Wireless ad hoc networks are autonomous, self-configurating and adaptive. Thus, such networks are excellent candidates for military tactical networks, where their ability to be operational rapidly and without any centralized entity is essential. As radio coverage is usually limited, multihop routing is often needed; this is achieved by an ad hoc routing protocol supporting nodes mobility. In this paper, we present performance measurements of the Optimized Link State Routing (OLSR) routing protocol, having the status of IETF RFC. The measurements are performed at CELAR site on a platform representative of military scenarios in urban areas. This platform consists of ten routers, eight PDAs and laptops using a IEEE 802.11b radio interface and implementing OLSR v7. Some nodes are mobile within vehicles. The emphasis of the measurements is on the performance of the network (route repair, network convergence speed, user traffic performance) in presence of this mobility.

A Coloured Petri Net Approach to Formalising and Analysing the Resource Reservation Protocol


 
 
 The goal of the Resource Reservation Protocol (RSVP) is to support the provision of the Quality of Service required for emerging Internet applications (such as video conferencing) that require a level of performance not guaranteed by the Internet. RSVP attempts to provide performance guarantees by establishing resource reservations (such as the number of buffers and bandwidth allocation) within routers and host computers of the Internet. Currently, Internet protocols are not formally specified when they are developed. Instead they are described in a narrative way in documents called Request for Comments(RFCs). This is the case for RSVP. To increase confidence in RSVP we have formalised and analysed its narrative specification using Coloured Petri Nets (CPNs). This paper demonstrates how CPNs can be used for modelling and analysing RSVP. Among the several beneficial features of CPNs are: graphical facilities for specification; support for different levels of abstraction; hierarchical structuring mechanisms; and verification and validation methods, such as querying the state space to investigate properties, and language equivalence to check the consistency of different levels of abstraction. Coloured Petri Nets are supported by a number of computer tools including Design/CPN. Design/CPN supports the construction and maintenance of CPN models and their simulation and analysis using state spaces. These facilities allow us to create a model that provides a clear, unambiguous and precise definition of RSVP, and to analyse the protocol for functional correctness. The paper concentrates on the approach and the tools used in this investigation.
 
 

Lightweight models for interpreting informal specifications

We explore the use of lightweight models, namely those in PROMELA/SPIN, by software engineers within the life cycle of software development. The primary goal is to improve the interpretation and understanding of an informal specification, not necessarily to validate the specification. We give details of an example involving an informal specification of an application protocol in telecommunications, namely the Request for Comments (RFC) standard for the Trivial File Transfer protocol (TFTP). We show how we were able to use this type of modelling in an iterative process, using tools that facilitate the process.

From dynamic IP transport service ordering to DiffServ network configuration

The Internet Engineering Task Force (IETF) proposes the Differentiated Services (DiffServ) architecture [IETF Request for Comments 2475, 1998] as a basic mechanism for providing QoS in the Internet. However, this is not enough. For a complete QoS solution, network and service management for DiffServ networks needs to be defined. In this paper, we describe the design, implementation, and evaluation of a QoS management system. The system allows a customer to dynamically order a guaranteed IP transport service from an Internet Service Provider over a Web-interface. The system then performs all the mappings and resource allocation steps needed. Finally, it configures IP DiffServ routers such that they provide the requested service. All levels and steps in the process are under policy-control, which allows for very flexible operation of the system. The system has been tested on a small lab internal test network. Finally, lessons learnt during the implementation and tests together with issues and problem with our approach on QoS management are described.

U.S. Sentencing Commission Summary of Proposed Emergency Amendments and Requests for Comment, November 27, 2002

U.S. Sentencing Commission Summary of Proposed Emergency Amendments and Requests for Comment, November 27, 2002

Telephone numbers, domain names, and ENUMbers

One of the biggest barriers to the development of public IP telephony services has been the lack of a universal addressing system. While IP-enabled devices have long been capable of originating phone and fax calls, it is difficult to call an IP device because they are hard to find. Internet Engineering Task Force (IETF) Request for Comments (RFC) 2916, E.164 Number and DNS, seeks to solve this problem in a simple and perhaps unlikely way. Simple, in that the ENUM protocol converts existing telephone numbers into domain names.The designers of ENUM hope to foster a global megadirectory of communications users who can be reached in any number of ways by means of only one number. While theoretically any character space could be standardized in an attempt to create a universal addressing scheme, ENUM explicitly adopts telephone numbers, presumably to take advantage of their global user acceptance and mature infrastructure. This choice adds a significant public policy dimension to the story. Far from being benign and boring, telephone numbers can present significant communications policy issues, and are regulated both domestically and internationally. The top level of this hierarchy is defined by International Telecommunication Union-Telecommunication Standardization Sector (ITU-T) Recommendation E.164.

Commercial Speech and Public Health: Request for Comment

Commercial Speech and Public Health: Request for Comment

A mobility management protocol for IP-based cellular networks

Mobile IP is an IETF RFC that supports transparent host migration on the Internet. In the transition to IP-based cellular networks, it is widely agreed that Mobile IP provides an elegant solution for inter-domain, or macro- mobility management, but lacks critical aspects of mobility management needed within cellular networks. The shortcomings have led to the recent emergence of micro- mobility management protocols. This paper presents an IP- based mobility management protocol, µ-Mobile IP, based on two enhancements, proactive handoff and paging support, to an Internet Draft proposal Regional Registrations. A signaling cost analysis is used to justify the need for such enhancements. We show through simulations the protocol's suitability for supporting real-time communications.

Remedies for common user-agent problems

User agents---that is browsers and other programs that deal with the Web---can fail the user in many ways. This article, by three people deeply involved with the development of the Web, documents some typical common user agent problems, and suggests correct ways of working.<BR><BR>The authors use several Web-specific technical terms, so let me list the important ones here:<BR><BR>• Fragment identifier: the part of a URI Web address after a `#' character, typically identifying a sub-part of a document (e.g. http://www.example.com/index.html#contact).<BR>• HTTP: hypertext transfer protocol - the protocol used for transferring documents between a server and a client.<BR>• Media type (also known as MIME type): an identifying string like "text/html" or "image/gif" used by servers and clients for identifying the type of a document.<BR>• PNG: a bitmapped image format, like GIF and JPEG, but with better user experience properties<BR>• RFC: `Request for comments' - the name given to Internet standards published by the IETF (Internet Engineering Task Force)<BR>• SVG: structured vector graphics: a non-bitmapped image format that scales better than bitmapped formats like PNG, GIF and JPEG.<BR>• URI: (Universal resource identifier) a `Web address', such as http://www.acm.org<BR>• URI scheme: the part of a URI before the colon, such as http: and ftp:<BR><BR>---Steven Pemberton

Performance evaluation of TCP algorithms in multi‐hop wireless packet networks

AbstractWireless packet ad hoc networks are characterized by multi‐hop wireless connectivity and limited bandwidth competed among neighboring nodes. In this paper, we investigate and evaluate the performance of several prevalent TCP algorithms in this kind of network over the wireless LAN standard IEEE 802.11 MAC layer. After extensively comparing the existing TCP versions (including Tahoe, Reno, New Reno, Sack and Vegas) in simulations, we show that, in most cases, the Vegas version works best. We reveal the reason why other TCP versions perform worse than Vegas and show a method to avoid this by tuning a TCP parameter— maximum window size. Furthermore, we investigate the performance of these TCP algorithms when they run with the delayed acknowledgment (DA) option defined in IETF RFC 1122, which allows the TCP receiver to transmit an ACK for every two incoming packets. We show that the TCP connection can gain 15 to 32 per cent good‐put improvement by using the DA option. For all the TCP versions investigated in this work, the simulation results show that with the maximum window size set at approximately 4, TCP connections perform best and then all these TCP variants differ little in performance. Copyright © 2001 John Wiley & Sons, Ltd.

Information Security Standards: Deluge and Dearth

Avalanche! With new information doubling every five years (soon to be every two and a half years!), the information security professional may find herself buried in an information avalanche. Where a new security standard in the financial services area could, in the past, safely take three to five years in the making, we now frown when it takes two years. Where we would, historically, rarely work on even two standards in parallel, we now must work on a dozen. Prior to 1986, the Internet Engineering Task Force (IETF) didn't exist. Today, we have thousands of Requests for Comment (RFC) documents, many of which are on the IETF standards track. With the American National Standards Institute (ANSI) accredited standards bodies, with the International Standards Organization (ISO), with the International Telecommunications Union (ITU), and other national and international standards bodies, the information security professional faces hundreds of security- or privacy-related standards, guidelines, or regulatory initiatives each year.

IP multicast routing through ATM networks

The purpose of this paper is to have a closer look at the ‘core’ technology providing interworking between connectionless TCP/IP internetworks and switched ATM networks. The scope of the paper is IP multicast, while the main focus is on the network side of multicast, more precisely, on layers three and two of Internet architecture dealing with IP multicast routing. The paper analyses both practically available solutions and those being currently under discussion in IETF as Internet drafts. As a background of this comparison, the possible convergence of IP and ATM multicast service models is discussed. Major conclusions, based on simulation studies and scalability analysis are: (i) the high mapping overhead requires a separate address resolution service for unicast and multicast addresses; and (ii) efficient convergence has to make obsolete classical IP over ATM (M. Laubach, Classical IP and ARP over ATM, Network Working Group, Request for Comments: 1577, Category: Standards Track, January, 1994 [1]) in order to permit ‘cut-through’ within the ATM domain.

On the Change of the Membership System of the Physical of Japan : Request for Comments

On the Change of the Membership System of the Physical of Japan : Request for Comments

World Intellectual Property Organization: Basic proposal for the substantive provisions of the treaty on intellectual property in respect of databases

The Reporters Committee for Freedom of the Press submitted these comments in response to the Patent and Trademark Office's request for comments on the Chairman's text of the Diplomatic Conference on Certain Copyright and Neighboring Rights Questions, to be held in Geneva from December 2 to 20, 1996. 1

The Sources of Ethical Decision Making for Individuals in the Public Sector

What was the value in changing ASPA's Code of Ethics? Until recently, the Code of Ethics of the American Society for Public Administration symbolized the confusion in the field rather than its insights. The fine content of the former code was lost in numerous, unequal categories and discursive language. The new code has five principles or decision-making sources upon which public administrators should draw. This article demonstrates how the five sources are prominently discussed in the literature and arc useful for practitioners. Even more, the new code should provide an authoritative framework for the field. At an elementary level, the code prohibits egregiously unethical behavior. At a more sophisticated level, the code recognizes that the really tough administrative decisions occur when two or more of the legitimate decision-making sources compete. Thus the code is far more than a list of legalistic prohibitions. It is a powerful tool for decision analysis on the one hand and an aspirational call for excellence in the profession on the other. The American Society for Public Administration (ASPA) recently streamlined and substantially revised its Code of Ethics so that it would be more useful for practitioners and better reflect the literature on public sector ethics. The new code collapses 12 categories of unequal importance into 5 overarching principles. In this article I provide the intellectual and scholarly background used in the selection of those five organizing principles. Historical Background of ASPA's Code of Ethics ASPA adopted a loose set of ethical principles in 1981. In 1984, ASPA approved a formal Code of Ethics which was expanded the next year to include implementation guidelines. When published in small type, the Code and Implementation Guidelines were two full pages. In 1993, ASPA's leadership encouraged the Professional Ethics Committee to revise the Code of Ethics. Although no specific charge was given, the following complaints were noted by the committee: 1. The highlighted principles did not distinguish between overarching principles and subordinate concepts and were too numerous to remember easily. 2. Despite good content, the code rambled and had inconsistent styles. 3. Because of the weak organization, it was difficult to find a specific point without reading the document from the beginning. The Professional Ethics Committee drew heavily on the previous 1985 code in its revision but decided to (1) use broader categories that would be recognizable to the scholarly community and memorable for the practitioner community; (2) consolidate the code into a dense, one-page document; and (3) number and display principles and points for ease of use. A subcommittee redrafted the code in the spring of 1994, then the full committee edited it, and a preliminary draft was shared with the National Council. In the fall, a draft was published in PA Times with a request for comments. After revising it based on the comments received, the revised Code of Ethics was unanimously adopted at the 1994 December meeting. Problems in Identifying Sources of Decision Making Which Are the Key Sources or Roles? One of the most commonly agreed-upon notions in the field is that administrators have numerous roles, or value sets, which are sources for the decisions they make. For example, an administrator may concentrate quite appropriately on legal issues at one point, organizational issues at another, and personal interests at still another. Although there is widespread agreement that these roles and their concomitant value sets exist, that agreement quickly dissipates when one tries to identify and name which roles or value sets are crucial for public administrators. Researchers have divided up an administrator's major roles in many ways. Some researchers are famous for specializing in a single area, even though their views are broad, such as Rohr's (1989) concentration on regime values (law and legal tradition) and Frederickson's (1990) attention to social equity (public interest), but many researchers have consciously divided the roles to cover all the major decision-making bases. …

Request for Comments on Policy on Promotion of Unapproved Uses

Request for Comments on Policy on Promotion of Unapproved Uses

Names and symbols for the transfermium elements request for comments on IUPAC provisional recommendations

Names and symbols for the transfermium elements request for comments on IUPAC provisional recommendations

Hazardous waste storage, disposal, remediation, and closure

Hazardous waste storage, disposal, remediation, and closure

SEQ 2001, RPAG, PROP and other Alphabet Soup

The lid of Pandora's Box has been lifted. Queensland, which takes pride in being different, is considering adopting a relatively conventional planning system — and in the process is raising issues which might never be adequately resolved. Until now, development in Queensland has been largely buffered against intervention by State planners, contributions towards social facilities and consultation with the public but all this could be about to change. In December 1990, a meeting at Parliament House convened by the then Minister for Housing and Local Government, Hon Tom Burns, set in train a process to investigate South East Queensland's needs for the coming decades — SEQ 2001. A Regional Planning Advisory Group (RPAG) was established which utilised a number of task forces and public consultation to canvass a wide range of topics while RPAG itself produced a ‘preferred pattern of urban development’ (PROP) and a complementary set of proposals for institutional change. The task force findings and the draft regional outline plan were presented to the public in July 1993 in a set of 19 reports with a request for comments by October 1993.