5A Survey on the Design, Applications, and Enhancementsof Application-Layer Overlay NetworksJINU KURIAN and KAMIL SARACUniversity of Texas at DallasThis article presents a survey of recent advancements in application-layer overlay networks. Some of themost important applications that have been proposed for overlays include multicast, QoS support, denial-of-service (DoS) defense, and resilient routing. We look at some of the important approaches proposed forthese applications and compare the advantages and disadvantages of these approaches. We also examinesome of the enhancements that have been proposed in overlay topology design, enhanced routing perfor-mance, failure resistance, and the issues related to coexistence of overlay and native layers in the Internet.We conclude the article with a comment on the purist vs pluralist argument of overlay networks that hasreceived much debate recently. Finally, we propose a new deployment model for service overlays that seeksto interpose between these two approaches.Categories and Subject Descriptors: C.2.1 [Computer-Communication Networks]: Network Architectureand Design; C.2.3 [Computer-Communication Networks]: Network OperationsGeneral Terms: Design, Economics, Performance, Reliability, SecurityAdditional Key Words and Phrases: Overlay networks, service overlay networks, performance, enhance-ments, deployment modelACM Reference Format:Kurian, J. and Sarac, K. 2010. A survey on the design, applications, and enhancements of application-layeroverlay networks. ACM Comput. Surv. 43, 1, Article 5 (November 2010), 34 pages.DOI = 10.1145/1824795.1824800 http://doi.acm.org/10.1145/1824795.18248001. INTRODUCTIONOver the last few years, overlay networks have garnered much interest in the researchand industrial community. This interest has been sparked primarily due to several dis-tinct advantages offered by overlay networks for the testing and deployment of noveland possibly disruptive applications in the Internet.Some of the proposed applications for overlay networks include multicast [Chuet al. 2000]; content delivery networks [Yu et al. 1999; Krishnamurthy et al. 2001;Su et al. 2006]; quality of service [Duan et al. 2003; Li and Mohapatra 2004b;Subramanian et al. 2004]; enhanced routing performance [Andersen et al. 2001;Anderson et al. 1999; Akamai a]; anonymity [Dingledine et al. 2004; Abe 1999;Authors’ address: J. Kurian (contact author; email: [email protected]), The University of Texas atDallas, Department of Computer Science, 800 West Campbell Road, Richardson, TX 75080-1407.Permission to make digital or hard copies of part or all of this work for personal or classroom use is grantedwithout fee provided that copies are not made or distributed for profit or commercial advantage and thatcopies show this notice on the first page or initial screen of a display along with the full citation. Copyrightsfor components of this work owned by others than ACM must be honored. Abstracting with credit is per-mitted. To copy otherwise, to republish, to post on servers, to redistribute to lists, or to use any componentof this work in other works requires prior specific permission and/or a fee. Permissions may be requestedfrom Publications Dept., ACM, Inc., 2 Penn Plaza, Suite 701, New York, NY 10121-0701 USA, fax +1 (212)869-0481, or [email protected]2010 ACM 0360-0300/2010/11-ART5 $10.00DOI 10.1145/1824795.1824800 http://doi.acm.org/10.1145/1824795.1824800ACM Computing Surveys, Vol. 43, No. 1, Article 5, Publication date: November 2010.5:2 J. Kurian and K. SaracFig. 1.Overlaymodel.Anonymizer ]; anycast [Freedman et al. 2006; Ballani and Francis 2005], IPv6 deploy-ment [6bone ]; testbeds [Chun et al. 2003; Touch et al. 2005]; denial of service (DoS)defense [Keromytis et al. 2002; Andersen 2003]; VoIP [Amir et al. 2005; Baset andSchulzrinne 2006]; reliable email [Agarwal et al. 2005]; distributed systems manage-ment [Liang et al. 2005]; and reliable name service lookup [Park et al. 2004]. Similarly,much work has gone into enhancing some of the important requirements associatedwith overlay networks like topology design, failure resistance, routing performance,Byzantine resilience, and native layer interaction.Before continuing with our main discussion, we first answer the question: What areoverlay networks and why are they required?An overlay network is a virtual network that is built on top of another. It is usuallybuilt (directly by end users or a third-party overlay service provider (OSP)) to providean application or service not easily provided by traditional methods to interested endusers. In general, overlay architectures consist of two layers: (1) the overlay layer com-prised of the overlay nodes and virtual links; and (2) the native layer over which theoverlay network is built. In the Internet today, the native layer is the IP layer whichprovides a best-effort delivery service between remote systems. The overlay layer iscomprised of a selection of the native layer’s nodes, logically interconnected in any de-sired manner. Figure 1 shows an example of an overlay network. In this article, weconcentrate on overlay networks built for the purpose of providing a specific applica-tion, as described above. For a detailed overview of peer-to-peer overlay networks, theinterested reader is referred to Lua et al. [2004].The amount of work that is related to overlay networks can be staggering to a novicereader. Yet, to date, there has been no concerted effort to survey the disparate appli-cations and the enhancements of generic overlay architectures. In this article, we aimto provide the reader with a comprehensive overview of the more significant applica-tions for overlay networks, the issues that arise with each of these applications andsome existing solutions to these issues. We also present recently proposed two mainviews, called the purist [Ratnasamy et al. 2005] and pluralist argument [Petersonet al. 2004], on the long-term impact of overlay networks in the Internet. While thepurist view sees overlay networks as testbeds for experimentation with novel networkarchitectures, the pluralist view considers overlays as an integral part of the futureInternet in providing value-added network services to end users.The main motivation behind the deployment of overlay networks is to counter manylimitations of the current Internet architecture that have become obvious [RatnasamyACM Computing Surveys, Vol. 43, No. 1, Article 5, Publication date:
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