Data Source: INSPEC

Accession number: 7696094

Title: Provisioning and restoration in the next-generation optical core

Author(s): Shen, L.; Ramamurthy, B.

Journal title: Optical Networks Magazine

Title of higher level publication: Opt. Netw. Mag. (Netherlands)

Volume: 4

Start Page: 32

Publication year: 2003

ISSN: 1388-6916

Abstract: Research is underway currently to develop intelligent control planes for the next-generation optical transport network, which can provide customers with automatic, flexible; and real-time provisioning as well as enhanced network survivability and interoperabilty. An intelligent optical core appears to be viable by incorporating Generalized Multiprotocol Label Switching (GMPLS) technology into the optical control plane and deploying reconfigurable optical network elements; such as reconfigurable optical crossconnects; tunable transceivers, anti reconfigurable optical add-drop multiplexers. Much of the work in this area has focused on proposing network architectures, solving the dynamic RWA problem, developing distributed protection/restoration schemes, standardizing network interfaces (e.g. UNI and NNI), and extending existing Internet routing/signaling protocols for WDM optical networks. We present an overview of the role of GMPLS in the next-generation optical core; concentrating on both the issues and the challenges in automatic lightpath provisioning and network restoration. First; we discuss the evolutionary trend and architectures of the next-generation optical network. Then, we present an overview of dynamic provisioning problems; followed by a discussion of various constraints and unique requirements for lightpath establishment in WDM optical networks. We close by discussing the challenges in optical network restoration

Controlled indexing: intelligent control; multiprotocol label switching; network interfaces; optical communication equipment; optical fibre networks; reviews; routing protocols; telecommunication network reliability; wavelength division multiplexing

Uncontrolled indexing: next-generation optical core; optical network provisioning; intelligent control planes; next-generation optical transport network; automatic provisioning; real-time provisioning; network survivability; network interoperability; Generalized Multiprotocol Label Switching; GMPLS technology; reconfigurable optical network elements; reconfigurable optical crossconnects; tunable transceivers; reconfigurable optical add-drop multiplexers; dynamic RWA problem solution; WDM optical networks; distributed protection/restoration; network interface standardization; Internet routing/signaling protocols; automatic lightpath provisioning; automatic network restoration; dynamic provisioning problems; lightpath establishment; optical network restoration; UNI; NNI

Classification codes: B6260F; B6260M; B6150M; B6150P

Data Source: INSPEC

Accession number: 7685792

Title: JOR: a Java Object Router

Author(s): Mohamed, N.; Davis, A.; Liu, X.; Ramamurthy, B.

Title of higher level publication: Proceedings of the 14th IASTED International Conference Parallel and Distributed Computing and Systems

Conference Title: PDCS 2002: 14th IASTED International Conference on Parallel and Distributed Computing and Systems

Start Page: 630

Publication year: 2002

Abstract: Content-based routing has emerged as a new routing paradigm, allowing messages to be routed based on defined fields within the message. Content-based routers generally employ XML. Each message is translated into XML when sent, and translated out of XML when received. Further, XML limits the objects sent to documents and messages. We introduce a content-based router that goes beyond messages to routing entire Java objects. The Java Object Router (JOR) separates routing mechanisms from routing policies making it easy to use in a variety of applications

Controlled indexing: client-server systems; Java; message passing; middleware; network routing; object-oriented programming; quality of service; transport protocols

Uncontrolled indexing: JOR; Java Object Router; message routing; content based routers; XML; extensible markup language; mobile objects; TCP network; IP network; transport control protocol; Internet protocol; weighted fair queuing scheduling; quality of service; QOS; client server program

Classification codes: C6150N; C5640; C6110J

Data Source: INSPEC

Accession number: 7644014

Title: An analytical model for virtual topology reconfiguration in optical networks and a case study

Author(s): Xi Yang; Ramamurthy, B.

Title of higher level publication: Proceedings Eleventh International Conference on Computer Communications and Networks (Cat. No.02EX594)

Conference Title: Proceedings Eleventh International Conference on Computer Communications and Networks

Start Page: 302

Publication year: 2002

Abstract: An analytical model for virtual topology reconfiguration (VTR) in optical networks is developed. It aims at the optical networks with a circuit-based data plane and an IP-like control plane. By identifying and analyzing the important factors impacting the network performance due to VTR operations on both planes, we can compare the benefits and penalties of different VTR algorithms and policies. The best VTR scenario can be adaptively chosen from a set of such algorithms and policies according to the real-time network situations. For this purpose, a cost model integrating all these factors is created to provide a comparison criterion independent of any specific VTR algorithm and policy. A case study based on simulation experiments is conducted to illustrate the application of our models

Controlled indexing: network topology; optical fibre networks

Uncontrolled indexing: virtual topology reconfiguration; optical networks; VTR; circuit-based data plane; IP-like control plane; network performance; policies; real-time network situations; cost model

Classification codes: B6260F; B6150P

Data Source: INSPEC

Accession number: 7395168

Title: Dynamic routing in translucent WDM optical networks

Author(s): Xi Yang; Ramamurthy, B.

Title of higher level publication: 2002 IEEE International Conference on Communications. Conference Proceedings. ICC 2002 (Cat. No.02CH37333)

Conference Title: Proceedings of IEEE International Conference on Communications

Start Page: 2796

Publication year: 2002

Abstract: Translucent WDM optical networks use sparse placement of regenerators to overcome the impairments and wavelength contention introduced by fully transparent networks, and achieve a performance close to fully opaque networks with much less cost. Our previous study proved the feasibility of translucent networks using the sparse regeneration technique. We addressed the placement of regenerators based on static schemes allowing only fixed number of regenerators at fixed locations. This paper furthers the study by proposing a suite of dynamical routing schemes. Dynamic allocation, advertisement and discovery of regeneration resources are proposed to support sharing transmitters and receivers between regeneration and access functions. This study follows the current trend in the optical networking industry by utilizing the extension of IP control protocols. Dynamic routing algorithms, aware of current regeneration resources and link states, are designed to smartly route the connection requests under quality constraints. A hierarchical network model, supported by the MPLS-based control plane, is also proposed to provide scalability. Experiments show that network performance is improved without placement of extra regenerators

Controlled indexing: optical fibre networks; optical receivers; optical repeaters; optical transmitters; packet switching; telecommunication network routing; transport protocols; wavelength division multiplexing

Uncontrolled indexing: dynamic routing; translucent WDM optical networks; sparse regenerators placement; wavelength contention; transparent networks; opaque networks; network performance; sparse regeneration; static schemes; dynamic allocation; regeneration resources advertisement; regeneration resources discovery; transmitters; receivers; access functions; regeneration functions; optical networking industry; IP control protocols; dynamic routing algorithms; link states; connection requests routing; quality constraints; hierarchical network model; MPLS-based control plane

Classification codes: B6150P; B6260M; B6260F; B6150M

Data Source: INSPEC

Accession number: 7395152

Title: Centralized vs. distributed connection management schemes under different traffic patterns in wavelength-convertible optical networks

Author(s): Lu Shen; Ramamurthy, B.

Title of higher level publication: 2002 IEEE International Conference on Communications. Conference Proceedings. ICC 2002 (Cat. No.02CH37333)

Conference Title: Proceedings of IEEE International Conference on Communications

Start Page: 2712

Publication year: 2002

Abstract: Centralized and distributed methods are two connection management schemes in wavelength convertible optical networks. In the earlier work, the centralized scheme is said to have lower network blocking probability than the distributed one. Hence, much of the previous work in connection management has focused on the comparison of different algorithms in only distributed scheme or in only centralized scheme. However, we believe that the network blocking probability of these two connection management schemes depends, to a great extent, on the network traffic patterns and reservation times. Our simulation results reveal that the performance improvement (in terms of blocking probability) of the centralized method over the distributed method is inversely proportional to the ratio of average connection inter-arrival time to reservation time. After that the ratio increases beyond a threshold, those two connection management schemes yield almost the same blocking probability under the same network load. In this paper, we review the working procedure of distributed and centralized schemes, discuss the tradeoff between them, compare these two methods under different network traffic patterns via simulation and give our conclusion based on the simulation data

Controlled indexing: optical fibre networks; optical wavelength conversion; telecommunication network management; telecommunication traffic; wavelength division multiplexing

Uncontrolled indexing: centralized connection management schemes; distributed connection management schemes; traffic patterns; wavelength-convertible optical networks; network blocking probability; reservation times; network load; network traffic patterns

Classification codes: B6260F; B6210C; B6260M

Data Source: INSPEC

Accession number: 7337487

Title: Sparse regeneration in a translucent WDM optical network

Author(s): Xi Yang; Ramamurthy, B.

Journal title: Proceedings of the SPIE - The International Society for Optical Engineering

Title of higher level publication: Proc. SPIE - Int. Soc. Opt. Eng. (USA)

Conference Title: APOC 2001: Asia-Pacific Optical and Wireless Communications. Optical Networking

Volume: 4585

Start Page: 61

Publication year: 2001

ISSN: 0277-786X

Abstract: Research implies that transparent optical WDM networks have difficulty in overcoming transmission impairments introduced by long-haul fibers and cascading optical components while opaque networks are not cost-efficient because a large number of wavelengths need optical-electronic and electronic-optical conversions at every intermediate node. This paper proposes an alternate approach to fully transparent and fully opaque optical networks for operating a wavelength routed optical network. The architecture of regeneration node that performs sparse regeneration (or translucency) is modeled. Both static and dynamic regeneration schemes are discussed. The regeneration demands generated from call blocking and signal quality requirements are addressed. Two implementation strategies for incorporating sparse regeneration are introduced and algorithms are proposed for the regenerator placement, and their relative merits are studied

Controlled indexing: network topology; optical fibre networks; optical repeaters; probability; telecommunication network routing; wavelength division multiplexing

Uncontrolled indexing: sparse regeneration; translucent WDM optical network; transmission impairments; long-haul fibers; cascading optical components; opaque optical networks; wavelength routed optical network; regeneration node architecture; dynamic regeneration; static regeneration; call blocking probability; signal quality; optical-electronic conversion; electronic-optical conversion; regenerator placement algorithms; bidirectional ring network; Pacific Bell network

Classification codes: B6260F; B6260M; B6150P; B6260C

Data Source: INSPEC

Accession number: 7300113

Title: Translucent optical WDM networks for the next-generation backbone networks

Author(s): Ramamurthy, B.; Yaragorla, S.; Xi Yang

Title of higher level publication: GLOBECOM'01. IEEE Global Telecommunications Conference (Cat. No.01CH37270)

Conference Title: GLOBECOM '01. IEEE Global Telecommunications Conference

Start Page: 60

Publication year: 2001

Abstract: This paper proposes an alternate approach to fully transparent and fully opaque optical networks for operating a wavelength routed optical network. The architecture of the regeneration node that performs sparse regeneration (or translucency) is discussed. The regeneration demands generated from call blocking and signal quality requirements are addressed. Two implementation strategies for incorporating sparse regeneration are introduced and their relative merits are studied

Controlled indexing: network topology; optical fibre networks; optical repeaters; probability; telecommunication network routing; wavelength division multiplexing

Uncontrolled indexing: translucent optical WDM networks; next-generation backbone networks; opaque optical networks; transparent optical networks; wavelength routed optical network; regeneration node architecture; sparse regeneration; call blocking; signal quality; BER; blocking probability; lightpaths; wavelength division multiplexing; static with topology algorithm

Classification codes: B6260F; B6260M; B6150P

Data Source: INSPEC

Accession number: 7279647

Title: A novel hybrid wavelength converter node architecture for WDM wavelengthrouted networks

Author(s): Jong Tae Lee; Ramamurthy, B.

Journal title: Optical Networks Magazine

Title of higher level publication: Opt. Netw. Mag. (Netherlands)

Volume: 3

Start Page: 31

Publication year: 2002

ISSN: 1388-6916

Abstract: Demand for network bandwidth has been increasing dramatically in recent years. Optical networks and the wavelength-division multiplexing (WDM) technique are promising technologies for satisfying the explosive bandwidth demand. In addition, the wavelength conversion mechanism, which transforms an input wavelength to a desirable wavelength at conversion nodes, eliminates the wavelength continuity constraint, and increases the network efficiency significantly. In this paper, we propose a novel wavelength convertible node architecture and a wavelength conversion method, hybrid wavelength conversion. Along with the new hybrid wavelength conversion mechanism, we examine five different wavelength converter utilization schemes and present the best wavelength converter utilization strategy. A heuristic for sparse wavelength converter placement is presented as a result of our wavelength converter placement strategy. Results obtained from our research show that our wavelength conversion framework improves the network performance significantly without substantially increasing the network costs

Controlled indexing: optical fibre networks; optical wavelength conversion; telecommunication network routing; wavelength division multiplexing

Uncontrolled indexing: hybrid node architecture; WDM; wavelength-routed networks; wavelength division multiplexing; network bandwidth; optical networks; hybrid wavelength conversion; sparse wavelength converter placement; network performance

Classification codes: B6260M; B6260F; B6150P

Data Source: INSPEC

Accession number: 7201836

Title: Design private (VPNs) optical of virtual networks over wavelength division multiplexed (WDM) networks

Author(s): Ramamurthy, B.; Ramakrishnan, A.

Journal title: Optical Networks Magazine

Title of higher level publication: Opt. Netw. Mag. (Netherlands)

Volume: 3

Start Page: 59

Publication year: 2002

ISSN: 1388-6916

Abstract: The bandwidth requirements of the Internet are increasing every day and there are newer and more bandwidth-thirsty applications emerging on the horizon. Wavelength division multiplexing (WDM) is the next step towards leveraging the capabilities of the optical fiber, especially for wide-area backbone networks. Virtual private networks are seen as the killer applications of tomorrow, and a great amount of research and development effort is being channeled into finding efficient ways for implementing them. In our work we introduce the notion of VPNs operating over optical wavelength-routed WDM backbone networks. We formulate the problem of VPN design over optical WDM networks as an integer linear problem. A new method to deal with traffic from diverse VPNs is introduced and its performance analyzed

Controlled indexing: Internet; optical fibre networks; telecommunication network routing; wavelength division multiplexing

Uncontrolled indexing: private virtual networks; VPN; WDM network; optical wavelength division multiplexed networks; bandwidth requirements; routing; Internet; wide-area backbone networks; killer applications; design; integer linear problem; traffic

Classification codes: B6210L; B6260M; B6260F; B6150P; C5620W

Data Source: INSPEC

Accession number: 7098795

Title: DiffServer: application level differentiated services for Web servers

Author(s): Rao, G.; Ramamurthy, B.

Title of higher level publication: ICC 2001. IEEE International Conference on Communications. Conference Record (Cat. No.01CH37240)

Conference Title: Proceedings of International Conference on Communications

Start Page: 1633

Publication year: 2001

Abstract: Web content hosting, in which a Web server stores and provides Web access to documents for different customers, is becoming increasingly common. For example, a Web server can host Web pages for several different companies and individuals. Traditionally, Web service providers (WSPs) provide all customers with the same level of performance (best-effort service). Most service differentiation has been in the pricing structure (individual vs. business rates) or the connectivity type (dial-up access vs. leased line, etc.). This report presents DiffServer, a program that implements two simple, server-side, application-level mechanisms (server-centric and client-centric) to provide different levels of Web service. The results of the experiments show that there is not much overhead due to the addition of this additional layer of abstraction between the client and the Apache Web server under light load conditions. Also, the average waiting time for high priority requests decreases significantly after they are assigned priorities as compared to a FIFO approach

Controlled indexing: file servers; Internet

Uncontrolled indexing: DiffServer; application level differentiated services; Web content hosting; Web pages; Web service providers; best-effort service; pricing structure; business rates; individual rates; dial-up access; leased line; application-level mechanisms; Apache Web server; average waiting time; high priority requests; FIFO approach; World Wide Web

Classification codes: B6210L; C5620W; C7210N

Data Source: INSPEC

Accession number: 7086152

Title: Hierarchy-based access control in distributed environments

Author(s): Birget, J.-C.; Zou, X.; Noubir, G.; Ramamurthy, B.

Title of higher level publication: ICC 2001. IEEE International Conference on Communications. Conference Record (Cat. No.01CH37240)

Conference Title: Proceedings of International Conference on Communications

Start Page: 229

Publication year: 2001

Abstract: Access control is a fundamental concern in any system that manages resources, e.g., operating systems, file systems, databases and communications systems. The problem we address is how to specify, enforce, and implement access control in distributed environments. This problem occurs in many applications such as management of distributed project resources, e-newspaper and pay TV subscription services. Starting from an access relation between users and resources, we derive a user hierarchy, a resource hierarchy, and a unified hierarchy. The unified hierarchy is then used to specify the access relation in a way that is compact and that allows efficient queries. It is also used in cryptographic schemes that enforce the access relation. We introduce three specific cryptography based hierarchical schemes, which can effectively enforce and implement access control and are designed for distributed environments because they do not need the presence of a central authority (except perhaps for setup)

Controlled indexing: access control; cryptography; distributed databases; distributed processing; publishing; telecommunication control; telecommunication network management; telecommunication security; television applications

Uncontrolled indexing: hierarchy-based access control; distributed environments; resource management; operating systems; file systems; distributed databases; communications systems; distributed project resources; e-newspaper; pay TV subscription services; user hierarchy; resource hierarchy; unified hierarchy; cryptography based hierarchical schemes

Classification codes: B6120D; B6210C; B6430J; C1260C; C6130S; C6160B; C6150N; C7230

Data Source: INSPEC

Accession number: 7086151

Title: Optimization of amplifier placements in switch-based optical networks

Author(s): Zhong, L.; Ramamurthy, B.

Title of higher level publication: ICC 2001. IEEE International Conference on Communications. Conference Record (Cat. No.01CH37240)

Conference Title: Proceedings of International Conference on Communications

Start Page: 224

Publication year: 2001

Abstract: Wavelength division multiplexing (WDM) offers a solution to the problem of exploiting the large bandwidth on optical links; it is the current favorite multiplexing technology for optical communication networks. Due to the high cost of an optical amplifier, it is desirable to strategically place the amplifiers throughout the network in a way that guarantees that all the signals are adequately amplified while minimizing the total number amplifiers being used. Previous studies all consider a star-based network. This paper demonstrates an original approach for solving the problem in switch-based WDM optical network assuming the traffic matrix is always the permutation of the nodes. First we formulate the problem by choosing typical permutations which can maximize the traffic load on individual links; then a GA (genetic algorithm) is used to search for feasible amplifier placements. Finally, by setting up all the lightpaths without violating the power constraints we confirm the feasibility of the solution

Controlled indexing: genetic algorithms; network topology; optical fibre amplifiers; optical fibre networks; optical switches; telecommunication traffic; wavelength division multiplexing

Uncontrolled indexing: amplifier placement optimization; wavelength division multiplexing; bandwidth; optical links; optical communication networks; optical amplifier; star-based network; switch-based WDM optical network; traffic matrix; network nodes permutation; traffic load; genetic algorithm; lightpaths; power constraints

Classification codes: B6260F; B6260M; B0260; B4320F

Data Source: INSPEC

Accession number: 6950160

Title: Virtual topology reconfiguration of wavelength-routed optical WDM networks

Author(s): Ramamurthy, B.; Ramakrishnan, A.

Title of higher level publication: Globecom '00 - IEEE. Global Telecommunications Conference. Conference Record (Cat. No.00CH37137)

Conference Title: Proceedings of Global Telecommunications Conference

Start Page: 1269

Publication year: 2000

Abstract: The bandwidth requirements of the Internet are increasing every day and there are newer and more bandwidth-thirsty applications emerging on the horizon. Wavelength division multiplexing (WDM) is the next step towards leveraging the capabilities of the optical fiber, especially for wide-area backbone networks. The ability to switch a signal at intermediate nodes in a WDM network based on their wavelengths is known as wavelength-routing. One of the greatest advantages of using wavelength-routing WDM is the ability to create a virtual topology different from the physical topology of the underlying network. This virtual topology can be reconfigured when necessary, to improve performance. We discuss the previous work done on virtual topology design and also discuss and propose different reconfiguration algorithms applicable under different scenarios

Controlled indexing: network topology; optical fibre networks; optimisation; telecommunication network routing; telecommunication traffic; wavelength division multiplexing; wide area networks

Uncontrolled indexing: wavelength-routed optical WDM networks; virtual topology reconfiguration; bandwidth; Internet; wavelength division multiplexing; optical fiber; wide-area backbone networks; intermediate nodes; performance; virtual topology design; reconfiguration algorithms; WAN; traffic pattern; optimization

Classification codes: B6260F; B6260M; B0260; B6150P

Data Source: INSPEC

Accession number: 6914017

Title: Design of virtual private networks (VPNs) over optical wavelength-division-multiplexed (WDM) networks

Author(s): Ramamurthy, B.; Ramakrishnan, A.

Journal title: Proceedings of the SPIE - The International Society for Optical Engineering

Title of higher level publication: Proc. SPIE - Int. Soc. Opt. Eng. (USA)

Conference Title: OptiComm 2000: Optical Networking and Communications

Volume: 4233

Start Page: 76

Publication year: 2000

ISSN: 0277-786X

Abstract: The bandwidth requirements of the Internet are increasing every day and there are newer and more bandwidth-thirsty applications emerging on the horizon. Wavelength division multiplexing (WDM) is the next step towards leveraging the capabilities of the optical fiber, especially for wide-area backbone networks. Virtual private networks are seen as the killer applications of tomorrow, and a great amount of research and development effort is being channeled into finding efficient ways for implementing them. In our work, we introduce the notion of VPNs operating over optical wavelength-routed WDM backbone networks. We formulate the problem of VPN design over optical WDM networks as an integer linear problem. A new method to deal with traffic from diverse VPNs is introduced and its performance analyzed

Controlled indexing: Internet; linear programming; optical fibre networks; telecommunication network routing; wavelength division multiplexing

Uncontrolled indexing: virtual private networks; optical wavelength-division-multiplexed networks; WDM networks; bandwidth requirements; Internet; wide-area backbone networks; design; integer linear problem; performance

Classification codes: B6260F; B6260M; B6210L; B6150P; B0260; C5620W; C5670; C1180

Data Source: INSPEC

Accession number: 6809209

Title: LSMAC vs. LSNAT: scalable cluster-based Web servers

Author(s): Gan, X.; Schroeder, T.; Goddard, S.; Ramamurthy, B.

Journal title: Cluster Computing

Title of higher level publication: Cluster Comput. (Netherlands)

Volume: 3

Start Page: 175

Publication year: 2000

ISSN: 1386-7857

Abstract: Server scalability is more important than ever in today's client/server dominated network environments. Recently, researchers have begun to consider cluster based computers using commodity hardware as an alternative to expensive specialized hardware for building scalable Web servers. The authors present performance results comparing two cluster based Web servers based on different server architectures: OSI layer two dispatching (LSMAC) and OSI layer three dispatching (LSNAT). Both cluster based server systems were implemented as application-space programs running on commodity hardware in contrast to other, similar, solutions which require specialized hardware/software. We point out the advantages and disadvantages of both systems. We also identify when servers should be clustered and when clustering will not improve performance

Controlled indexing: client-server systems; file servers; Internet; open systems; workstation clusters

Uncontrolled indexing: LSMAC; LSNAT; scalable cluster based Web servers; server scalability; client/server dominated network environments; cluster based computers; commodity hardware; specialized hardware; server architectures; OSI layer two dispatching; OSI layer three dispatching; cluster based server systems; application-space programs

Classification codes: B6210L; C6150N; C5620W; C5690; C7210N

Data Source: INSPEC

Accession number: 6715740

Title: LSMAC and LSNAT: two approaches for cluster-based scalable Web servers

Author(s): Xuehong Gan; Schroeder, T.; Goddard, S.; Ramamurthy, B.

Title of higher level publication: 2000 IEEE International Conference on Communications. ICC 2000. Global Convergence Through Communications. Conference Record

Conference Title: Proceedings of IEEE International Conference on Communications

Start Page: 1164

Publication year: 2000

Abstract: Server responsiveness and scalability are more important than ever in today's client/server dominated network environments. Researchers have begun to consider cluster-based computers using commodity hardware as an alternative to expensive specialized hardware for building scalable Web servers. In this paper, we present performance results comparing two cluster-based Web servers based on different server infrastructures: MAC-based dispatching (LSMAC) and IP-based dispatching (LSNAT). Both cluster-based server systems were implemented as application-space programs running on commodity hardware. We point out the advantages and disadvantages of both systems. We also identify when servers should be clustered and when clustering will not improve performance

Controlled indexing: access protocols; application program interfaces; client-server systems; performance evaluation; search engines; transport protocols

Uncontrolled indexing: LSMAC; LSNAT; cluster-based scalable Web servers; server responsiveness; server scalability; client/server network; cluster-based computers; commodity hardware; performance results; server infrastructures; MAC-based dispatching; IP-based dispatching; application-space programs; World Wide Web

Classification codes: B6210L; B6150M; C7250N; C7210N; C5620W; C5640; C5670

Data Source: INSPEC

Accession number: 6712489

Title: LSMAC: an improved load sharing network service dispatcher

Author(s): Xuehong Gann; Ramamurthy, B.

Journal title: World Wide Web

Title of higher level publication: World Wide Web (Netherlands)

Volume: 3

Start Page: 53

Publication year: 2000

ISSN: 1386-145X

Abstract: The rapid growth of the Internet is changing the way we do business. Electronic commerce (or e-commerce) is already a reality and will expand rapidly in the near future. However, the success of e-commerce depends heavily on the scalability and availability of the servers. Cluster-based servers using commodity hardware have been accepted as a good alternative to expensive specialized hardware for building scalable services. In this paper, we summarize the two clustering architectures: IP-based clustering and MAC-based clustering. A new efficient implementation of the MAC-based clustering architecture is presented and its performance in clustering Web servers was measured using the WebStone benchmark and was found to be superior to that of existing MAC-based clustering implementations

Controlled indexing: electronic commerce; information resources; Internet; search engines

Uncontrolled indexing: Internet; load sharing network service dispatcher; LSMAC; electronic commerce; cluster-based servers; IP-based clustering architecture; MAC-based clustering architecture; Web servers; WebStone benchmark

Classification codes: C7250N; C7210N; C7120

Data Source: INSPEC

Accession number: 6635618

Title: Routing and wavelength assignment (RWA) with power considerations in all-optical wavelength-routed networks

Author(s): Ali, M.; Ramamurthy, B.; Deogun, J.S.

Title of higher level publication: Seamless Interconnection for Universal Services. Global Telecommunications Conference. GLOBECOM'99. (Cat. No.99CH37042)

Conference Title: Seamless Interconection for Universal Services. Global Telecommunications Conference. GLOBECOM'99

Start Page: 1433

Publication year: 1999

Abstract: Routing and wavelength assignment (RWA) is an important problem that arises in wavelength division multiplexed (WDM) optical networks. Previous studies have solved many variations of this problem under the assumption of perfect conditions regarding the power of a signal. We investigate this problem while allowing for degradation of routed signals by components such as taps, multiplexers, and fiber links. We assume that optical amplifiers are preplaced. We investigate the problem of routing the maximum number of connections while maintaining proper power levels. The problem is formulated as a mixed-integer nonlinear program and two-phase hybrid solution approaches employing two different heuristics are developed

Controlled indexing: integer programming; optical fibre amplifiers; optical fibre networks; telecommunication network routing; wavelength division multiplexing

Uncontrolled indexing: routing and wavelength assignment; power considerations; WDM optical networks; all-optical wavelength-routed networks; signal power; routed signals degradation; taps; multiplexers; fiber links; optical amplifiers; power levels; mixed-integer nonlinear program; two-phase hybrid solution; heuristics

Classification codes: B6260F; B6260M; B6150P; B0260; B4320F

Data Source: INSPEC

Accession number: 6631931

Title: Routing and wavelength assignment with power considerations in optical networks

Author(s): Ali, M.; Ramamurthy, B.; Doegun, J.S.

Journal title: Computer Networks

Title of higher level publication: Comput. Netw. (Netherlands)

Volume: 32

Start Page: 539

Publication year: 2000

ISSN: 1389-1286

Abstract: Previous studies have solved many variations of the routing and wavelength assignment (RWA) problem in optical networks under the assumption of perfect conditions regarding the power of a signal. In this paper, we investigate the RWA problem while allowing for degradation of routed signals by optical components. The problem is formulated as a mixed-integer nonlinear program. We propose a two-phase approach. In the first phase, we solve the pure RWA problem using fixed routes for every connection. In the second phase, power assignment is accomplished by either using a heuristic or using a genetic algorithm. This paper demonstrates that: (i) connections do interact affecting the power of each other, and (ii) global search meta-heuristics provide better solutions

Controlled indexing: genetic algorithms; heuristic programming; integer programming; nonlinear programming; optical fibre networks; power control; search problems; telecommunication control; telecommunication network routing; wavelength division multiplexing

Uncontrolled indexing: optical networks; routing and wavelength assignment; signal degradation; mixed-integer nonlinear program; power assignment; heuristic algorithm; genetic algorithm; global search meta-heuristics; connection interaction; WDM

Classification codes: B6260F; B6260M; B6150P; B0260

Data Source: INSPEC

Accession number: 6602098

Title: Scalable Web server clustering technologies

Author(s): Schroeder, T.; Goddard, S.; Ramamurthy, B.

Journal title: IEEE Network

Title of higher level publication: IEEE Netw. (USA)

Volume: 14

Start Page: 38

Publication year: 2000

ISSN: 0890-8044

Abstract: The exponential growth of the Internet, coupled with the increasing popularity of dynamically generated content on the World Wide Web, has created the need for more and faster Web servers capable of serving the over 100 million Internet users. Server clustering has emerged as a promising technique to build scalable Web servers. We examine the seminal work, early products, and a sample of contemporary commercial offerings in the field of transparent Web server clustering. We broadly classify transparent server clustering into three categories

Controlled indexing: information resources; Internet; search engines

Uncontrolled indexing: scalable Web server clustering; Internet; World Wide Web; Web servers; commercial products; seminal work; early products; transparent Web server clustering

Classification codes: B6210L; C7250N; C7210N; C5620W

Data Source: INSPEC

Accession number: 6497937

Title: Routing algorithms for all-optical networks with power considerations: the unicast case

Author(s): Ali, M.; Ramamurthy, B.; Deogun, J.S.

Title of higher level publication: Proceedings Eight International Conference on Computer Communications and Networks (Cat. No.99EX370)

Conference Title: Proceedings of IC3N'99: Eighth International Conference on Computer Communications and Networks

Start Page: 237

Publication year: 1999

Abstract: In this paper, we investigate the problem of routing connections in ail-optical networks while allowing for degradation of routed signals by different optical components. To overcome the complexity of the problem, we divide it into two parts. First, we solve the pure RWA problem using fixed routes for every connection. Second, power assignment is accomplished by either using the smallest-gain first (SGF) heuristic or using a genetic algorithm. Numerical examples on a wide variety of networks show that: (a) the number of connections established without considering the signal attenuation was most of the time greater than that achievable considering attenuation; and (b) the genetic solution quality was much better than that of SGF, especially when the conflict graph of the connections generated by the linear solver is denser

Controlled indexing: genetic algorithms; graph theory; optical fibre networks; telecommunication network routing; wavelength division multiplexing

Uncontrolled indexing: routing algorithms; all-optical networks; unicast case; optical components; RWA problem; power assignment; smallest-gain first heuristic; genetic algorithm; signal attenuation; solution quality; dense conflict graph; linear solver; routing and wavelength assignment; WDM

Classification codes: B6260F; B6150P; B6260M

Data Source: INSPEC

Accession number: 6484811

Title: SIMON: a simulator for optical networks

Author(s): Ramamurthy, B.; Datta, D.; Feng, H.; Heritage, J.P.; Mukherjee, B.

Journal title: Proceedings of the SPIE - The International Society for Optical Engineering

Title of higher level publication: Proc. SPIE - Int. Soc. Opt. Eng. (USA)

Conference Title: All-Optical Networking 1999: Architecture, Control, and Management Issues

Volume: 3843

Start Page: 130

Publication year: 1999

ISSN: 0277-786X

Abstract: SIMON is an object-oriented event-driven simulation package implemented in C++ which incorporates optical device characteristics in the measurement of network-level blocking statistics. SIMON is suitable for studying the performance of large wavelength-routed optical networks, in which a call is set up in the network for a specific duration on a pre-determined lightpath. Currently the physical-layer models allow for modeling phenomena such as signal attenuation in fiber and other components, amplifier gain saturation, and homowavelength crosstalk in switches. Simulation experiments can be performed with a user-specified bit-error rate limit, which must be satisfied by any call set up in the network

Controlled indexing: C++ language; discrete event simulation; error statistics; object-oriented methods; optical fibre networks; software packages; telecommunication computing

Uncontrolled indexing: SIMON; object-oriented event-driven simulation package; C++; optical device characteristics; optical networks; network-level blocking statistics; performance; large wavelength-routed optical networks; pre-determined lightpath; physical-layer models; modeling phenomena; signal attenuation; amplifier gain saturation; homowavelength crosstalk; switches; user-specified bit-error rate limit

Classification codes: B6260F; C7410F; C6185; C6110J

Data Source: INSPEC

Accession number: 6398612

Title: Impact of transmission impairments on the teletraffic performance of wavelength-routed optical networks

Author(s): Ramamurthy, B.; Datta, D.; Feng, H.; Heritage, J.P.; Mukherjee, B.

Journal title: Journal of Lightwave Technology

Title of higher level publication: J. Lightwave Technol. (USA)

Volume: 17

Start Page: 1713

Publication year: 1999

ISSN: 0733-8724

Abstract: In a wavelength-routed optical network, a transmitted signal remains in the optical domain over the entire route (lightpath) assigned to it between its source and destination nodes. The optical signal may have to traverse a number of crossconnect switches (XCSs), fiber segments, and optical amplifiers, e.g., erbium-doped fiber amplifiers (EDFAs). Thus, while propagating through the network, the signal may degrade in quality as it encounters crosstalk at the XCSs and also picks up amplified spontaneous emission (ASE) noise at the EDFAs. Since these impairments continue to degrade the signal quality as it progresses toward its destination, the received bit error rate (BER) at the destination node might become unacceptably high. Previous work on the lightpath routing and wavelength assignment (RWA) problem assumed an ideal physical layer and ignored these transmission impairments. The main contribution of our work is to incorporate the role of the physical layer in setting up lightpaths by employing appropriate models of multiwavelength optical devices (XCSs and EDFAs) such that the BER of a candidate lightpath can be computed, in advance, to determine if this lightpath should be used for the call. Features from existing RWA algorithms are integrated with our on-line BER calculation mechanism. Our simulation studies indicate that employing BER-based call-admission algorithms has a significant impact on the performance of realistic networks

Controlled indexing: errors; optical crosstalk; optical fibre amplifiers; optical fibre networks; optical noise; superradiance; telecommunication network routing; telecommunication traffic

Uncontrolled indexing: transmission impairments; teletraffic performance; wavelength-routed optical networks; transmitted signal; optical domain; entire route; lightpath; destination nodes; optical signal; crossconnect switches; erbium-doped fiber amplifiers; fiber segments; crosstalk; amplified spontaneous emission noise; signal quality; received bit error rate; destination node; lightpath routing; wavelength assignment problem; multiwavelength optical devices; RWA algorithms; simulation studies; call-admission algorithms

Classification codes: B6260F; B6150P; B6220B; B4320F

Data Source: INSPEC

Accession number: 6390001

Title: Transparent vs. opaque vs. translucent wavelength-routed optical networks

Author(s): Ramamurthy, B.; Feng, H.; Datta, D.; Heritage, J.P.; Mukherjee, B.

Title of higher level publication: OFC/IOOC'99. Optical Fiber Communication Conference and the International Conference on Integrated Optics and Optical Fiber Communications (Cat. No.99CH36322)

Conference Title: OFC/IOOC'99. Optical Fiber Communication Conference and the International Conference on Integrated Optics and Optical Fiber Communications

Start Page: 59

Publication year: 1999

Abstract: This study evaluates the relative merits of three approaches (transparency, opacity, and translucency) for establishing calls in a wavelength-routed optical network. Call-admission algorithms employ online bit-error-rate computation and include the effects of transmission impairments

Controlled indexing: opacity; optical fibre networks; telecommunication congestion control; telecommunication network routing; transparency; wavelength division multiplexing

Uncontrolled indexing: wavelength routing; optical network; call admission algorithm; bit error rate; transparency; opacity; translucency

Classification codes: B6260F; B6150P; B6260M; B6150C

Data Source: INSPEC

Accession number: 6159942

Title: Optimizing amplifier placements in a multiwavelength optical LAN/MAN: the unequally powered wavelengths case

Author(s): Ramamurthy, B.; Iness, J.; Mukherjee, B.

Journal title: IEEE/ACM Transactions on Networking

Title of higher level publication: IEEE/ACM Trans. Netw. (USA)

Volume: 6

Start Page: 755

Publication year: 1998

ISSN: 1063-6692

Abstract: Optical networks based on passive-star couplers and employing WDM have been proposed for deployment in local and metropolitan areas. These networks suffer from splitting, coupling, and attenuation losses. Since there is an upper bound on transmitter power and a lower bound on receiver sensitivity, optical amplifiers are usually required to compensate for the power losses mentioned above. Due to the high cost of amplifiers, it is desirable to minimize their total number in the network. However, an optical amplifier has constraints on the maximum gain and the maximum output power it can supply; thus, optical amplifier placement becomes a challenging problem. In fact, the general problem of minimizing the total amplifier count is a mixed-integer nonlinear problem. Previous studies have attacked the amplifier-placement problem by adding the "artificial" constraint that all wavelengths, which are present at a particular point in a fiber, be at the same power level. This constraint simplifies the problem into a solvable mixed-integer linear program. Unfortunately, this artificial constraint can miss feasible solutions that have a lower amplifier count but do not have the equally powered wavelengths constraint. In this paper, we present a method to solve the minimum-amplifier-placement problem, while avoiding the equally powered wavelength constraint. We demonstrate that, by allowing signals to operate at different power levels, our method can reduce the number of amplifiers required

Controlled indexing: linear programming; metropolitan area networks; minimisation; network topology; nonlinear programming; optical fibre amplifiers; optical fibre LAN; wavelength division multiplexing

Uncontrolled indexing: amplifier placements; multiwavelength optical LAN; unequally powered wavelengths case; passive-star couplers; WDM; splitting; coupling; attenuation losses; transmitter power; receiver sensitivity; optical amplifiers; power losses; maximum gain; maximum output power; optical amplifier placement; mixed-integer nonlinear problem; multiwavelength optical MAN

Classification codes: B6260F; B6210L; B0260; B6260M; B6150P; C5620L; C5620M; C1180

Data Source: INSPEC

Accession number: 6071837

Title: Wavelength conversion in WDM networking

Author(s): Ramamurthy, B.; Mukherjee, B.

Journal title: IEEE Journal on Selected Areas in Communications

Title of higher level publication: IEEE J. Sel. Areas Commun. (USA)

Volume: 16

Start Page: 1061

Publication year: 1998

ISSN: 0733-8716

Abstract: Wavelength conversion has been proposed for use in wavelength-division multiplexed networks to improve efficiency. This study highlights systems challenges and performance issues which need to be addressed in order to incorporate wavelength conversion effectively. A review/survey of the enabling technologies, design methods, and analytical models used in wavelength-convertible networks is provided

Controlled indexing: optical fibre networks; optical frequency conversion; optoelectronic devices; reviews; telecommunication network management; telecommunication network routing; wavelength division multiplexing

Uncontrolled indexing: WDM networking; wavelength conversion; wavelength-division multiplexed networks; efficiency; performance; review/survey; design methods; analytical models; wavelength-convertible networks; optoelectronic devices; wavelength-routed network design; management algorithms; routing algorithms

Classification codes: B6260; B6150C; B4340; B6150P; B6210C

Data Source: INSPEC

Accession number: 6029351

Title: Optimizing amplifier placements in a multiwavelength optical LAN/MAN: the equally powered-wavelengths case

Author(s): Ramamurthy, B.; Iness, J.; Mukherjee, B.

Journal title: Journal of Lightwave Technology

Title of higher level publication: J. Lightwave Technol. (USA)

Volume: 16

Start Page: 1560

Publication year: 1998

ISSN: 0733-8724

Abstract: Wavelength division multiplexing (WDM) provides the ability to utilize the enormous bandwidth offered by optical networks, using today's electronics. WDM-based optical networks employing passive-star couplers have been proposed for deployment in local and metropolitan areas. Optical amplification is often required in such networks to compensate for the signal attenuation along the fiber links and the splitting and coupling losses in the network. However, an optical amplifier has constraints on the maximum gain and the maximum output power it can supply; thus optical amplifier placement becomes a challenging problem. A simplifying assumption for analytical tractability requires that all wavelengths, present at a particular point in a fiber, be at the same power level, viz, the equally powered-wavelengths case. However, previous studies did not minimize the total number of amplifiers while achieving power equalization. In this paper, we formulate the minimization of amplifiers with power equalization as a mixed integer linear program (MILP) that can be solved by a linear program solver. Illustrative examples on sample networks are presented, which demonstrate the characteristics and the advantages of our optimal amplifier placement algorithm

Controlled indexing: compensation; fibre lasers; metropolitan area networks; optical fibre LAN; optical fibre losses; wavelength division multiplexing

Uncontrolled indexing: amplifier placement optimisation; multiwavelength optical LAN; multiwavelength optical MAN; equally powered-wavelengths case; wavelength division multiplexing; optical networks; electronics; WDM-based optical networks; passive-star couplers; optical amplification; signal attenuation compensation; fiber links; splitting losses; coupling losses; optical amplifier; maximum gain; maximum output power; optical amplifier placement; power equalization; mixed integer linear program; linear program solver; optimal amplifier placement algorithm

Classification codes: B6260; B6150C; B6230; B6210L; B4320F; C5620L; C5620M

Data Source: INSPEC

Accession number: 5998517

Title: BER-based call admission in wavelength-routed optical networks

Author(s): Datta, D.; Ramamurthy, B.; Feng, H.; Heritage, J.P.; Mukherjee, B.

Title of higher level publication: OFC '98. Optical Fiber Communication Conference and Exhibit. Technical Digest. Conference Edition. 1998 OSA Technical Digest Series Vol.2 (IEEE Cat. No.98CH36177)

Conference Title: OFC '98 Optical Fiber Communication Conference and Exhibit. Technical Digest Conference Edition 1998 OSA Technical Digest Series. Vol.2

Start Page: 92

Publication year: 1998

Abstract: The objective of the present work is to estimate the on-line BER on candidate routes and wavelengths before setting up a call. Note that the existence of other calls currently in progress, i.e., traffic variation, will affect the BER estimate (because they will affect the cross talk in cross connect switches (XCSs) and the wavelength dependence and saturation of gains and ASE noise generation in EDFAs)

Controlled indexing: fibre lasers; optical crosstalk; optical fibre networks; optical noise; telecommunication congestion control; telecommunication network routing

Uncontrolled indexing: BER-based call admission; wavelength-routed optical networks; on-line BER; candidate routes; traffic variation; BER estimate; cross talk; cross connect switches; wavelength dependence; gain saturation; ASE noise generation; EDFAs

Classification codes: B6260; B6150P; B6220B; B4320F

Data Source: INSPEC

Accession number: 5911744

Title: Minimizing the number of optical amplifiers needed to support a multi-wavelength optical LAN/MAN

Author(s): Ramamurthy, B.; Iness, J.; Mukherjee, B.

Title of higher level publication: Proceedings IEEE INFOCOM '97. The Conference on Computer Communications. Sixteenth Annual Joint Conference of the IEEE Computer and Communications Societies. Driving the Information Revolution (Cat. No.97CB36034)

Conference Title: Proceedings of INFOCOM '97

Start Page: 261

Publication year: 1997

Abstract: Optical networks based on passive star couplers and employing wavelength-division multiplexing (WDM) have been proposed for deployment in local and metropolitan areas. Amplifiers are required in such networks to compensate for the power losses due to splitting and attenuation. However, an optical amplifier has constraints on the maximum gain and the maximum output power it can supply; thus optical amplifier placement becomes a challenging problem. The general problem of minimizing the total amplifier count, subject to the device constraints, is a mixed-integer nonlinear problem. Previous studies have attacked the amplifier-placement problem by adding the "artificial" constraint that all wavelengths, which are present at a particular point in a fiber, be at the same power level. In this paper, we present a method to solve the minimum-amplifier-placement problem while avoiding the equally-powered-wavelength constraint. We demonstrate-that, by allowing signals to operate at different power levels, our method can reduce the number of amplifiers required in several small to medium-sized networks

Controlled indexing: fibre lasers; integer programming; metropolitan area networks; minimisation; network topology; nonlinear programming; optical fibre LAN; wavelength division multiplexing

Uncontrolled indexing: multi-wavelength optical LAN; multi-wavelength optical MAN; optical networks; passive star couplers; wavelength-division multiplexing; WDM; metropolitan area networks; local area networks; power losses; splitting; attenuation; maximum gain; maximum output power; optical amplifier placement; mixed-integer nonlinear problem; power level; minimum-amplifier-placement problem; equally-powered-wavelength constraint; small sized networks; medium-sized networks

Classification codes: B6260; B6210L; B0260; B6150C; B6150P; C5620L; C5620M; C1180

Data Source: INSPEC

Accession number: 5707705

Title: Optical components for WDM lightwave networks

Author(s): Borella, M.S.; Jue, J.P.; Banerjee, D.; Ramamurthy, B.; Mukherjee, B.

Journal title: Proceedings of the IEEE

Title of higher level publication: Proc. IEEE (USA)

Volume: 85

Start Page: 1274

Publication year: 1997

ISSN: 0018-9219

Abstract: Recently, there has been growing interest in developing optical fiber networks to support the increasing bandwidth demands of multimedia applications, such as video conferencing and World Wide Web browsing. One technique for accessing the huge bandwidth available in an optical fiber is wavelength-division multiplexing (WDM). Under WDM, the optical fiber bandwidth is divided into a number of nonoverlapping wavelength bands, each of which may be accessed at peak electronic rates by an end user. By utilizing WDM in optical networks, we can achieve link capacities on the order of 50 THz. The success of WDM networks depends heavily on the available optical device technology. This paper is intended as a tutorial on some of the optical device issues in WDM networks. It discusses the basic principles of optical transmission in fiber and reviews the current state of the art in optical device technology. It introduces some of the basic components in WDM networks, discusses various implementations of these components, and provides insights into their capabilities and limitations. Then, this paper demonstrates how various optical components can be incorporated into WDM optical networks for both local and wide-area applications. Finally, the paper provides a brief review of experimental WDM networks that have been implemented

Controlled indexing: computer networks; laser beam applications; optical communication equipment; optical fibre networks; optical frequency conversion; wavelength division multiplexing

Uncontrolled indexing: optical components; WDM lightwave networks; optical fiber networks; multimedia applications; wavelength division multiplexing; link capacities; optical device technology; review

Classification codes: B6260; B6230H; B6210L; B4360; B4340; B4125

Data Source: INSPEC

Accession number: 5319047

Title: Elimination of all-optical cycles in wavelength-routed optical networks

Author(s): Iness, J.; Ramamurthy, B.; Mukherjee, B.; Bala, K.

Journal title: Journal of Lightwave Technology

Title of higher level publication: J. Lightwave Technol. (USA)

Volume: 14

Start Page: 1207

Publication year: 1996

ISSN: 0733-8724

Abstract: A transparent (wide-area) wavelength-routed optical network may be constructed by using wavelength cross-connect switches connected together by fiber to form an arbitrary mesh structure. The network is accessed through electronic stations that are attached to some of these cross-connects. These wavelength cross-connect switches have the property that they may configure themselves into unspecified states. Each input port of a switch is always connected to some output port of the switch whether or not such a connection Is required for the purpose of information transfer. Due to the presence of these unspecified states, there exists the possibility of setting up unintended all-optical cycles in the network (viz., a loop with no terminating electronics in it). If such a cycle contains amplifiers [e.g., erbium-doped fiber amplifiers (EDFA's)], there exists the possibility that the net loop gain is greater than the net loop loss. The amplified spontaneous emission (ASE) noise from amplifiers can build up in such a feedback loop to saturate the amplifiers and result in oscillations of the ASE noise in the loop. Such all-optical cycles as defined above (and hereafter referred to as "white" cycles) must be eliminated from an optical network in order for the network to perform any useful operation. Furthermore, for the realistic case in which the wavelength cross-connects result in signal crosstalk, there is a possibility of having closed cycles with oscillating crosstalk signals. We examine algorithms that set up new transparent optical connections upon request while avoiding the creation of such cycles in the network. These algorithms attempt to find a route for a connection and then (in a post-processing fashion) configure switches such that white cycles that might get created would automatically get eliminated. In addition, our call-set-up algorithms can avoid the possibility of crosstalk cycles

Controlled indexing: broadband networks; laser feedback; laser noise; optical crosstalk; optical fibre networks; optical switches; oscillations; superradiance; telecommunication network routing; transparency; wavelength division multiplexing

Uncontrolled indexing: all-optical cycles; wavelength-routed optical networks; transparent wide-area wavelength-routed optical network; wavelength cross-connect switches; arbitrary mesh structure; output port; information transfer; erbium-doped fiber amplifiers; net loop gain; net loop loss; amplified spontaneous emission noise; feedback loop; fiber amplifier saturation; ASE noise; oscillating crosstalk signals; signal crosstalk; post-processing fashion; white cycles; crosstalk cycles

Classification codes: B6260; B6150C; B6230; B6150P; B6220B