360 research outputs found
Service level agreement framework for differentiated survivability in GMPLS-based IP-over-optical networks
In the next generation optical internet, GMPLS based IP-over-optical networks, ISPs will be required to support a wide variety of applications each having their own requirements. These requirements are contracted by means of the SLA. This paper describes a recovery framework that may be included in the SLA contract between ISP and customers in order to provide the required level of survivability. A key concern with such a recovery framework is how to present the different survivability alternatives including recovery techniques, failure scenario and layered integration into a transparent manner for customers. In this paper, two issues are investigated. First, the performance of the recovery framework when applying a proposed mapping procedure as an admission control mechanism in the edge router considering a smart-edge simple-core GMPLS-based IP/WDM network is considered. The second issue pertains to the performance of a pre-allocated restoration and its ability to provide protected connections under different failure scenarios
Network protection with multiple availability guarantees
We develop a novel network protection scheme that provides guarantees on both the fraction of time a flow has full connectivity, as well as a quantifiable minimum grade of service during downtimes. In particular, a flow can be below the full demand for at most a maximum fraction of time; then, it must still support at least a fraction q of the full demand. This is in contrast to current protection schemes that offer either availability-guarantees with no bandwidth guarantees during the downtime, or full protection schemes that offer 100% availability after a single link failure. We develop algorithms that provide multiple availability guarantees and show that significant capacity savings can be achieved as compared to full protection. If a connection is allowed to drop to 50% of its bandwidth for 1 out of every 20 failures, then a 24% reduction in spare capacity can be achieved over traditional full protection schemes. In addition, for the case of q = 0, corresponding to the standard availability constraint, an optimal pseudo-polynomial time algorithm is presented.National Science Foundation (U.S.) (NSF grants CNS-1116209)National Science Foundation (U.S.) (NSF grants CNS-0830961)United States. Defense Threat Reduction Agency (grant HDTRA-09-1-005)United States. Defense Threat Reduction Agency (grant HDTRA1-07-1-0004)United States. Air Force (Air Force contract # FA8721-05-C-0002
Time Shared Optical Network (TSON): a novel metro architecture for flexible multi-granular services
This paper presents the Time Shared Optical Network (TSON) as metro mesh network architecture for guaranteed, statistically-multiplexed services. TSON proposes a flexible and tunable time-wavelength assignment along with one-way tree-based reservation and node architecture. It delivers guaranteed sub-wavelength and multi-granular network services without wavelength conversion, time-slice interchange and optical buffering. Simulation results demonstrate high network utilization, fast service delivery, and low end-to-end delay on a contention-free sub-wavelength optical transport network. In addition, implementation complexity in terms of Layer 2 aggregation, grooming and optical switching has been evaluated
Architectures and protocols for sub-wavelength optical networks: contributions to connectionless and connection-oriented data transport
La rĂ pida evoluciĂł d’Internet i l’à mplia gamma de noves aplicacions (per exemple, multimèdia, videoconferència, jocs en lĂnia, etc.) ha fomentat canvis revolucionaris en la manera com ens comuniquem. A mĂ©s, algunes d’aquestes aplicacions demanden grans quantitats de recursos d’ample de banda amb diversos requeriments de qualitat de servei (QoS).
El desenvolupament de la multiplexaciĂł per divisiĂł de longitud d’ona (WDM) en els anys noranta va fer molt rendible la disponibilitat d’ample de banda. Avui dia, les tecnologies de commutaciĂł òptica de circuits sĂłn predominants en el nucli de la xarxa, les quals permeten la configuraciĂł de canals (lightpaths) a travĂ©s de la xarxa. No obstant això, la granularitat d’aquests canals ocupa tota la longitud d’ona, el que fa que siguin ineficients per a proveir canals de menor ample de banda (sub-longitud d’ona). Segons la comunitat cientĂfica, Ă©s necessari augmentar la transparència dels protocols, aixĂ com millorar l’aprovisionament d’ample de banda de forma dinĂ mica. Per tal de fer això realitat, Ă©s necessari desenvolupar noves arquitectures. La commutaciĂł òptica de rĂ fegues i de paquets (OBS/OPS), sĂłn dues de les tecnologies proposades.
Aquesta tesi contribueix amb tres arquitectures de xarxa destinades a millorar el transport de dades sub-longitud d’ona. En primer lloc, aprofundim en la naturalesa sense connexió en OBS. En aquest cas, la xarxa incrementa el seu dinamisme a causa de les transmissions a rà fega. A més, les col·lisions entre rà fegues degraden el rendiment de la xarxa fins i tot a cà rregues molt baixes. Per fer front a aquestes col·lisions, es proposa un esquema de resolució de col·lisions pro actiu basat en un algorisme d’encaminament i assignació de longitud d’ona (RWA) que balanceja de forma automà tica i distribuïda la cà rrega en la xarxa. En aquest protocol, el RWA i la transmissió de rà fegues es basen en l’explotació i exploració de regles de commutació que incorporen informació sobre contencions i encaminament. Per donar suport a aquesta arquitectura, s’utilitzen dos tipus de paquets de control per a l’encaminament de les rà fegues i l’actualització de les regles de commutació, respectivament. Per analitzar els beneficis del nou algorisme, s’utilitzen quatre topologies de xarxa diferents. Els resultats indiquen que el mètode proposat millora en diferents marges la resta d’algorismes RWA en funció de la topologia i sense penalitzar altres parà metres com el retard extrem a extrem.
La segona contribuciĂł proposa una arquitectura hĂbrida sense i orientada a connexiĂł sobre la base d’un protocol de control d’accĂ©s al medi (MAC) per a xarxes OBS (DAOBS). El MAC ofereix dos mètodes d’accĂ©s: arbitratge de cua (QA) per a la transmissiĂł de rĂ fegues sense connexiĂł, i pre-arbitratge (PA) per serveis TDM orientats a connexiĂł. Aquesta arquitectura permet una Ă mplia gamma d’aplicacions sensibles al retard i al bloqueig. Els resultats avaluats a travĂ©s de simulacions mostren que en l’accĂ©s QA, les rĂ fegues de mĂ©s alta prioritat tenen garantides zero pèrdues i latències d’accĂ©s molt baixes. Pel que fa a l’accĂ©s PA, es reporta que la duplicaciĂł de la cĂ rrega TDM augmenta en mĂ©s d’un ordre la probabilitat de bloqueig, però sense afectar en la mateixa mesura les rĂ fegues sense connexiĂł. En aquest capĂtol tambĂ© es tracten dos dels problemes relacionats amb l’arquitectura DAOBS i el seu funcionament. En primer lloc, es proposa un model matemĂ tic per aproximar el retard d’accĂ©s inferior i superior com a conseqüència de l’accĂ©s QA. En segon lloc, es formula matemĂ ticament la generaciĂł i optimitzaciĂł de les topologies virtuals que suporten el protocol per a l’escenari amb trĂ fic estĂ tic.
Finalment, l’última contribuciĂł explora els beneficis d’una arquitectura de xarxa òptica per temps compartit (TSON) basada en elements de cĂ lcul de camins (PCE) centralitzats per tal d’evitar col·lisions en la xarxa. Aquesta arquitectura permet garantir l’aprovisionament orientat a connexiĂł de canals sub-longitud d’ona. En aquest capĂtol proposem i simulem tres arquitectures GMPLS/PCE/TSON. A causa del enfocament centralitzat, el rendiment de la xarxa depèn en gran mesura de l’assignaciĂł i aprovisionament de les connexions. Amb aquesta finalitat, es proposen diferents algorismes d’assignaciĂł de ranures temporals i es comparen amb les corresponents formulacions de programaciĂł lineal (ILP) per al cas estĂ tic. Per al cas de trĂ fic dinĂ mic, proposem i avaluem mitjançant simulaciĂł diferents heurĂstiques. Els resultats mostren els beneficis de proporcionar flexibilitat en els dominis temporal i freqĂĽencial a l’hora d’assignar les ranures temporals.The rapid evolving Internet and the broad range of new data applications (e.g., multimedia, video-conference, online gaming, etc.)
is fostering revolutionary changes in the way we communicate. In addition, some of these applications demand for unprecedented
amounts of bandwidth resources with diverse quality of service (QoS).
The development of wavelength division multiplexing (WDM) in the 90's made very cost-effective the availability of bandwidth.
Nowadays, optical circuit switching technologies are predominant in the core enabling the set up of lightpaths across the network.
However, full-wavelength lightpath granularity is too coarse, which results to be inefficient for provisioning sub-wavelength
channels. As remarked by the research community, an open issue in optical networking is increasing the protocol transparency as
well as provisioning true dynamic bandwidth allocation at the network level. To this end, new architectures are required. Optical
burst/packet switching (OBS/OPS) are two such proposed technologies under investigation.
This thesis contributes with three network architectures which aim at improving the sub-wavelength data transport from different
perspectives. First, we gain insight into the connectionless nature of OBS. Here, the network dynamics are increased due to the
short-lived burst transmissions. Moreover, burst contentions degrade the performance even at very low loads. To cope with them,
we propose a proactive resolution scheme by means of a distributed auto load-balancing routing and wavelength assignment
(RWA) algorithm for wavelength-continuity constraint networks. In this protocol, the RWA and burst forwarding is based on the
exploitation and exploration of switching rule concentration values that incorporate contention and forwarding desirability
information. To support such architecture, forward and backward control packets are used in the burst forwarding and updating
rules, respectively. In order to analyze the benefits of the new algorithm, four different network topologies are used. Results
indicate that the proposed method outperforms the rest of tested RWA algorithms at various margins depending on the topology
without penalizing other parameters such as end-to-end delay.
The second contribution proposes a hybrid connectionless and connection-oriented architecture based on a medium access control
(MAC) protocol for OBS networks (DAOBS). The MAC provides two main access mechanisms: queue arbitrated (QA) for
connectionless bursts and pre-arbitrated (PA) for TDM connection-oriented services. Such an architecture allows for a broad range
of delay-sensitive applications or guaranteed services. Results evaluated through simulations show that in the QA access mode
highest priority bursts are guaranteed zero losses and very low access latencies. Regarding the PA mode, we report that doubling
the offered TDM traffic load increases in more than one order their connection blocking, slightly affecting the blocking of other
connectionless bursts. In this chapter, we also tackle two of the issues related with the DAOBS architecture and its operation.
Firstly, we model mathematically the lower and upper approximations of the access delay as a consequence of the connectionless
queue arbitrated access. Secondly, we formulate the generation of the virtual light-tree overlay topology for the static traffic case.Postprint (published version
A Survey on the Path Computation Element (PCE) Architecture
Quality of Service-enabled applications and services rely on Traffic Engineering-based (TE) Label Switched Paths (LSP) established in core networks and controlled by the GMPLS control plane. Path computation process is crucial to achieve the desired TE objective. Its actual effectiveness depends on a number of factors. Mechanisms utilized to update topology and TE information, as well as the latency between path computation and resource reservation, which is typically distributed, may affect path computation efficiency. Moreover, TE visibility is limited in many network scenarios, such as multi-layer, multi-domain and multi-carrier networks, and it may negatively impact resource utilization. The Internet Engineering Task Force (IETF) has promoted the Path Computation Element (PCE) architecture, proposing a dedicated network entity devoted to path computation process. The PCE represents a flexible instrument to overcome visibility and distributed provisioning inefficiencies. Communications between path computation clients (PCC) and PCEs, realized through the PCE Protocol (PCEP), also enable inter-PCE communications offering an attractive way to perform TE-based path computation among cooperating PCEs in multi-layer/domain scenarios, while preserving scalability and confidentiality. This survey presents the state-of-the-art on the PCE architecture for GMPLS-controlled networks carried out by research and standardization community. In this work, packet (i.e., MPLS-TE and MPLS-TP) and wavelength/spectrum (i.e., WSON and SSON) switching capabilities are the considered technological platforms, in which the PCE is shown to achieve a number of evident benefits
Multiservice QoS-Enabled MAC for Optical Burst Switching
The emergence of a broad range of network-driven applications (e.g., multimedia, online gaming) brings in the need for a network environment able to provide multiservice capabilities with diverse quality-of-service (QoS) guarantees. In this paper, a medium access control protocol is proposed to support multiple services and QoS levels in optical burst-switched mesh networks without wavelength conversion. The protocol provides two different access mechanisms, queue-arbitrated and prearbitrated for connectionless and connection-oriented burst transport, respectively. It has been evaluated through extensive simulations and its simplistic form makes it very promising for implementation and deployment. Results indicate that the protocol can clearly provide a relative quality differentiation for connectionless traffic and guarantee null (or negligible, and thus acceptable) burst loss probability for a wide range of network (or offered) load while ensuring low access delay for the higher-priority traffic. Furthermore, in the multiservice scenario mixing connectionless and connection-oriented burst transmissions, three different prearbitrated slot scheduling algorithms are evaluated, each one providing a different performance in terms of connection blocking probability. The overall results demonstrate the suitability of this architecture for future integrated multiservice optical networks
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