141 research outputs found
Improving reliability in multi-layer networks with Network Coding Protection
© 2014 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.A major concern among network providers is to endow their networks with the ability to withstand and recover from failures. In recent years, there is a trend in network research referred to as Network Coding Protection (NCP). NCP combines the use of network coding techniques with a proactive protection scheme with the aim of improving network reliability. Although today's network backbone is a multi-layer network formed by the convergence of IP/MPLS and Optical technologies, the information available in the literature related to the performance of NCP schemes in multi-layer network scenarios is yet scarce. In this paper, we propose a novel NCP scheme referred to as DPNC+. The novelty of DPNC+ is that it exploits cross-layer information in order to improve the reliability of multi-layer (IP/MPLS over Optical) networks against link failures. Our evaluation results show that reduction up to 50% -related to protection cost- can be obtained when using the proposed scheme compared to conventional proactive protection techniques.This work was supported by the Spanish Ministry of Economy under contract TEC2012-34682, and the Catalan Research Council (CIRIT) under contract 2009 SGR1508.Peer ReviewedPostprint (author's final draft
Investigation of performance issues affecting optical circuit and packet switched WDM networks
Optical switching represents the next step in the evolution of optical networks. This thesis describes work that was carried out to examine performance issues which can occur in two distinct varieties of optical switching networks.
Slow optical switching in which lightpaths are requested, provisioned and torn down when no longer required is known as optical circuit switching (OCS). Services enabled by OCS
include wavelength routing, dynamic bandwidth allocation and protection switching. With network elements such as reconfigurable optical add/drop multiplexers (ROADMs) and
optical cross connects (OXCs) now being deployed along with the generalized multiprotocol label switching (GMPLS) control plane this represents the current state of the art in commercial networks. These networks often employ erbium doped fiber amplifiers (EDFAs) to boost the optical signal to noise ratio of the WDM channels and as channel configurations change, wavelength dependent gain variations in the EDFAs can lead to channel power
divergence that can result in significant performance degradation. This issue is examined in detail using a reconfigurable wavelength division multiplexed (WDM) network testbed and results show the severe impact that channel reconfiguration can have on transmission
performance.
Following the slow switching work the focus shifts to one of the key enabling technologies for fast optical switching, namely the tunable laser. Tunable lasers which can switch on the nanosecond timescale will be required in the transmitters and wavelength converters of optical packet switching networks. The switching times and frequency drifts, both of commercially available lasers, and of novel devices are investigated and performance issues which can arise due to this frequency drift are examined. An optical packet switching transmitter based on a novel label switching technique and employing one of the fast tunable lasers is designed and employed in a dual channel WDM packet switching system. In depth
performance evaluations of this labelling scheme and packet switching system show the detrimental impact that wavelength drift can have on such systems
Teleprotection signalling over an IP/MPLS network
Protection of electricity networks have developed to incorporate communications, referred to as protection signalling. Due to the evolution of the electricity supply system, there are many developments pending within the scope of protection signalling and protection engineering in general. This project investigates the use of current and emerging communications technologies (i.e. packetised networks) being applied and incorporated into current protection signalling schemes and technologies.
The purpose of the project is to provide a more cost-effective solution to protection schemes running obsolescent hardware. While the medium-term goal of the industry is to move entirely to IEC 61850 communications, legacy teleprotection relays using non-IP communications will still exist for many years to come. For companies to be ready for an IEC 61850 rollout a fully deployed IP/MPLS network will be necessary and it can be seen that various companies worldwide are readying themselves in this way. However, in the short-term for these companies, this means maintaining their existing TDM network (which runs current teleprotection schemes) and IP/MPLS network. This is a costly business outcome that can be minimised with the migration of services from and decommissioning of TDM networks.
Network channel testing was the primary testing focus of the project. The testing proved that teleprotection traffic with correct QoS markings assured the system met latency and stability requirements. Furthermore, MPLS resiliency features (secondary LSPs & Fast-reroute) were tested and proved automatic path failover was possible under fault conditions at sub-30ms speeds
NOC 2004 proceedings:NOC 2004 Proceedings : 9th European conference on networks & optical communications, Technical University of Eindhoven (TUE), Eindhoven, The Netherlands, June 29 - July 1, 2004
NOC 2004 proceedings:NOC 2004 Proceedings : 9th European conference on networks & optical communications, Technical University of Eindhoven (TUE), Eindhoven, The Netherlands, June 29 - July 1, 2004
Using GRASP and GA to design resilient and cost-effective IP/MPLS networks
The main objective of this thesis is to find good quality solutions for representative instances of the problem of designing a resilient and low cost IP/MPLS network, to be deployed over an existing optical transport network. This research is motivated by two complementary real-world application cases, which comprise the most important commercial and academic networks of Uruguay. To achieve this goal, we performed an exhaustive analysis of existing models and technologies. From all of them we took elements that were contrasted with the particular requirements of our counterparts. We highlight among these requirements, the need of getting solutions transparently implementable over a heterogeneous network environment, which limit us to use widely standardized features of related technologies. We decided to create new models more suitable to fit these needs. These models are intrinsically hard to solve (NP-Hard). Thus we developed metaheuristic based algorithms to find solutions to these real-world instances. Evolutionary Algorithms and Greedy Randomized Adaptive Search Procedures obtained the best results. As it usually happens, real-world planning problems are surrounded by uncertainty. Therefore, we have worked closely with our counterparts to reduce the fuzziness upon data to a set of representative cases. They were combined with different strategies of design to get to scenarios, which were translated into instances of these problems. Finally, the algorithms were fed with this information, and from their outcome we derived our results and conclusions
Planning tools for MPLS networks
Verkot, joissa MPLS-tekniikkaa (Multi Protocol Label Switching) käytetään pakettien reitittämiseen, kasvavat jatkuvasti yhä suuremmiksi ja toiminnallisuus, jota verkoissa tarvitaan, monipuolistuu koko ajan. Tämän syyn vuoksi verkon suunnittelija tarvitsee yhä parempia apuvälineitä, jotta suunnittelu olisi onnistunutta, optimaalista ja tuottaisi halutun tuloksen. Tämän diplomityön tarkoitus on selvittää tärkeimmät toiminnallisuudet ja ominaisuudet, joita MPLS-verkkojen suunnitteluun laadittu työkalu vaatii.
Diplomityö on jaettu kolmeen osaan. Ensimmäisessä osassa valotetaan MPLS-verkkojen käyttämää tekniikkaa. Tuossa osiossa käydään läpi tekniikat ja protokollat, joita MPLS-verkot käyttävät erinäisiin tehtäviin. Ensin käydään läpi yleisesti miksi MPLS-tekniikkaa ylipäätään tarvitaan ja miksi sitä käytetään verkkojen reitittämiseen. Tämän jälkeen tarkastellaan MPLS-protokollan otsikkokenttää ja sen osien käyttötarkoitukset selitetään. Sitten tarkastellaan MPLS-verkon rakennetta ja siihen kuuluvia laitteita. Seuraavaksi siirrytään osioon, joka selvittää kaikki yleisesti MPLS-polkujen rakentamiseen käytettävät protokollat ja miten ne eroavat toisistaan. Tämän jälkeen kerrotaan MPLS-vuonohjauksesta Differentiated Services-tekniikan avulla ja siitä miten se auttaa erilaisten liikenneluokkien erittelyssä MPLS-liikenteessä. Viimeinen kohta tässä osassa listaa erilaiset VPN-yhteydet, jotka ovat mahdollisia MPLS-tekniikkaa käytettäessä. Osio selventää näiden tekniikoiden eroavaisuudet ja mahdollisuudet, joita nämä MPLS-tekniikan avulla toteutettavat VPN-yhteydet suovat verrattuna aiempiin VPN-toteutuksiin.
Toinen osa tässä diplomityössä kertoo verkon suunnittelusta. Ensin käydään läpi verkon suunnittelua yleisellä tasolla. Tämä osa sisältää verkon suunnittelun eri vaiheet pääosittain: erilaiset ennustusmallit esitellään ja selvitetään mitoituksen ja vuonohjauksen rooli verkkosuunnittelussa. Näiden jälkeen siirrytään yleisestä verkonsunnittelusta osioihin, joita käytetään MPLS-verkon suunnittelussa ja joiden yleisesti oletetaan tai halutaan löytyvän MPLS-verkkoihin tarkoitetusta suunnittelutyökalusta. Viimeinen kohta kertoo toiminnallisuus- ja skaalautuvuushaasteista, joihin MPLS:n on tekniikkana vastattava nykypäivänä.
Kolmannessa osiossa tarkastellaan kahta eri suunnittelutyökalua, jotka on laadittu MPLS-verkkojen suunnitelua varten: WANDL-yhtiön julkaisemaa IP/MPLSView:ta ja Aria Networks Oy:n julkaisemaa iVNT:ta. Tässä osiossa käydään läpi näiden työkalujen toiminnallisuutta kertomalla erilaisista simulaatiomahdollisuuksista, joita kumpikin työkalu tarjoaa. Lisäksi kerrotaan mitä toimintoja ja protokollia näihin työkaluihin on mallinnettu, miten hyvin työkalut skaalautuvat kaupallisten MPLS-verkkojen tarpeisiin ja minkälaisita moduuleista työkalut on rakennettu.
Työn lopussa on pohdittu näiden kolmen osion perusteella, että mitkä ominaisuudet tulisi ottaa huomioon MPLS-verkon suunnittelutyökalua laadittaessa ja millä tavalla nämä ominaisuudet tulisi toteuttaa työkalussa. Näiden jälkeen on työhön vielä tehty loppuyhteenveto, joka kertoo työ tuloksista ja mahdollisista jatkokehitysmahdollisuuksista.
MPLS-verkon suunnittelu koostuu monesta eri vaiheesta, ja jokainen vaihe sisältää suuren määrän toiminnallisuusvaatimuksia. Nämä toiminnallisuusvaatimukset on mallinnettava MPLS-verkkojen suunnitteluun laaditussa työkalussa, jos halutaan että työkalu pystyy mallintamaan koko verkon suunnitteluprosessin alusta loppuun.
Tärkeimmät toiminnallisuudet, jotka MPLS-verkon suunnittelutyökalun tulee omata ovat simulointimahdollisuudet MPLS-poluille (LSP:t), MPLS-TE:lle, eri VPN-tyypeille ja DiffServ-liikenteelle, sillä nämä ovat tärkeimmät toiminnallisuudet MPLS-verkoissa tänä päivänä. Jos edellä mainittu toiminnallisuus on toteutettu ja mallinnettu suunnittelutyökalussa ja työkalu osaa optimoida liikennettä hyvin saadaan verkon pääoma- ja operaationaaliset kulut laskemaan. MPLS-verkon suunnittelutyökalua laadittaessa on myös tärkeää ottaa huomioon työkalun skaalautuvuusominaisuudet. Runkoverkot voivat koostua tänä päivänä tuhansista solmuista ja sadoista tuhansista liikennevirroista, joten suunnitelutyökalun tulisi omata toiminnallisuutta joka automatisoi joitain vaiheita verkonsuunnittelussa, mikä mahdollistaa tämän kokoluokan verkkojen suunnittelun. Tällainen toiminnallisuus voisi esimerkiksi olla automatisoitu vuonohjaus ja verkkojen topologiakokonaisuuden vienti ja tuonti suunnittelutyökaluun ja siitä ulos. /Kir1
Redundancy in Communication Networks for Smart Grids
Traditional electric power grids are currently undergoing fundamental changes: Representative examples are the increase in the penetration of volatile and decentralized renewable-energy sources and the emerging distributed energy-storage systems. These changes are not viable without the introduction of automation in grid monitoring and control, which implies the application of information and communication technologies (ICT) in power systems. Consequently, there is a transition toward smart grids. IEEE defines smart grid as follows: "The integration of power, communications, and information technologies for an improved electric power infrastructure serving loads while providing for an ongoing evolution of end-use applications" . The indispensable components of the future smart grids are the communication networks. Many well-established techniques and best practices, applied in other domains, are revisited and applied in new ways. Nevertheless, some gaps still need to be bridged due to the specific requirements of the smart-grid communication networks. Concretely, a challenging objective is to fulfill reliability and low-delay requirements over the wide-area networks, commonly used in smart grids. The main ``playground" for the work presented in this thesis is the smart-grid pilot of the EPFL campus. It is deployed on the operational medium-voltage distribution network of the campus. At the time of the writing of this thesis, the real-time monitoring of this active distribution network has been already put in place, as the first step toward the introduction of control and protection. The monitoring infrastructure relies on a communication network that is a representative example of the smart-grid communication networks. Keeping all this in mind, in this thesis, the main topic that we focus on, is the assurance of data communication over redundant network-infrastructure in industrial environments. This thesis consists of two parts that correspond to the two aspects of the topic that we address. In the first part of the thesis, we evaluate existing, well-established, technologies and solutions in the context of the EPFL smart-grid pilot. We report on the architecture of the communication network that we built on our campus. In addition, we go into more detail by reporting on some of the characteristics of the devices used in the network. We also discuss security aspects of the MPLS Transport Profile (MPLS-TP) which is one of the proposed technologies in the context of smart grids. In the second part of this thesis, we propose new solutions. While designing our campus smart-grid network, we analyzed the imposed requirements and recognized the need for a solution for reliable packet delivery within stringent delay constraints over a redundant network-infrastructure. The existing solutions for exploiting network redundancy, such as the parallel redundancy protocol (PRP), are not viable for IP-layer wide-area networks, a key element of emerging smart grids. Other solutions (MPLS-TP for example) do not meet the stringent delay requirement. To address this issue, we present a transport-layer solution: the IP-layer parallel redundancy protocol (iPRP). In the rest of the thesis, we analyze the methods for implementing fail-independent paths that are fundamental for the optimal operation of iPRP, in SDN-based networks. We also evaluate the benefits of iPRP in wireless environments. We show that, with a help of iPRP, the performance of the communication based on the Wi-Fi technology can be significantly improved
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