Abstract���Multihoming in combination with route optimization tools working in short timescales i... more Abstract���Multihoming in combination with route optimization tools working in short timescales is becoming a common practice in order to improve end-to-end QoS at the edge of the Internet. Nevertheless, the stability repercussions of these selfish practices under massive utilization are absolutely unpredictable. Therefore, self-adaptive mechanisms will be inevitable if masses of completely independent and uncoordinated multihomed stub Autonomous Systems are allowed to simultaneously change their interdomain traffic ...
This paper describes and evaluates the performance of a combined intra-and inter-domain routing m... more This paper describes and evaluates the performance of a combined intra-and inter-domain routing model for optical networks. The model is supported by a set of network components called Inter-Domain Routing Agents (IDRAs). Each domain or Autonomous System allocates one or more of these agents, which are the ones responsible for computing and finding constrained inter-domain lightpaths. Each IDRA exchanges with its peers two kinds of information, i.e, reachability information and network state information. In order to provide a highly scalable routing model, the network state information exchanged among the IDRAs is highly aggregated. In this particular work we introduce two opaque additive metrics which are used by the IDRAs to asses: i) the wavelength occupancy across domains; and ii) the resilience capabilities of downstream domains. Aggregating information at the domain boundaries aids in terms of overall scalability, but clearly, the frequency of this information exchange in order to keep the opaque metrics updated, needs to be tightly controlled. Our simulation results show that the opaque-aggregation scheme we are proposing in this paper is robust to the frequency of these updates.
This paper presents a technical overview of VPLS (Virtual Private LAN Service), its current state... more This paper presents a technical overview of VPLS (Virtual Private LAN Service), its current state of the art, its strengths and weaknesses, and most important of all, several open issues and future research work.
This paper describes and evaluates the performance of a combined intra-and inter-domain routing m... more This paper describes and evaluates the performance of a combined intra-and inter-domain routing model for optical networks. The model is supported by a set of network components called Inter-Domain Routing Agents (IDRAs). Each domain or Autonomous System allocates one or more of these agents, which are the ones responsible for computing and finding constrained inter-domain lightpaths. Each IDRA exchanges with its peers two kinds of information, i.e, reachability information and network state information. In order to provide a highly scalable routing model, the network state information exchanged among the IDRAs is highly aggregated. In this particular work we introduce two opaque additive metrics which are used by the IDRAs to asses: i) the wavelength occupancy across domains; and ii) the resilience capabilities of downstream domains. Aggregating information at the domain boundaries aids in terms of overall scalability, but clearly, the frequency of this information exchange in order to keep the opaque metrics updated, needs to be tightly controlled. Our simulation results show that the opaque-aggregation scheme we are proposing in this paper is robust to the frequency of these updates.
We show that a modified version of a path-vector protocol can drastically reduce the blocking and... more We show that a modified version of a path-vector protocol can drastically reduce the blocking and converge significantly faster, while exchanging less number of routing messages both during failure-free conditions and during a convergence.
31st European Conference on Optical Communications (ECOC 2005), 2005
Automatically Switched Optical Networks (ASON) specifications strongly recommends a hierarchical ... more Automatically Switched Optical Networks (ASON) specifications strongly recommends a hierarchical network architecture. In this paper authors propose three hierarchical routing algorithms, aiming to optimize the global network performance, while guaranteeing scalability.
We present a distributed routing algorithm for finding two disjoint (primary and backup) QoS path... more We present a distributed routing algorithm for finding two disjoint (primary and backup) QoS paths that run across multiple domains. Our work is inspired by the recent interest in establishing communication paths with QoS constrains spanning multiple IP/MPLS domains. In such settings, the routing decisions in each domain are made by the Path Computation Element (PCE). We assume that the PCEs run a joint distributed routing protocol, decoupled from the BGP, which enables them to establish efficient paths across multiple domains.
Optical networks provide a clear opportunity to redesign the multi-domain routing paradigm. This ... more Optical networks provide a clear opportunity to redesign the multi-domain routing paradigm. This paper reviews the current limitations in multi-domain routing as well as some of the research lines in the optical area.
Multi-Protocol Label Switching (MPLS) has become the core switching infrastructure at the intra-d... more Multi-Protocol Label Switching (MPLS) has become the core switching infrastructure at the intra-domain level. However, little progress has been made to extend the reach of MPLS Label Switched Paths (LSPs) across domains. Among the problems that remain unsolved is how to efficiently find and establish primary and protection inter-domain LSPs for mission-critical services subject to QoS constraints. In this paper we first review the major limitations impeding the deployment of these kinds of LSPs across multiple domains. Next, we discuss about the advantages of the recently proposed Path Computation Element (PCE)based architecture, and overview how this architecture can be exploited to tackle some of the main limitations exposed. Finally, we report the key features of a distributed routing scheme that we have recently proposed. This distributed routing approach allows a source PCE to count with sufficient information so as to find and establish optimal disjoint QoS paths across multiple domains in an efficient way. [1]. The advantages of MPLS are not confined only to integration and efficient switching of IP packets. Indeed, the available implementations of MPLS offer a suite of value-added features, which have been key drivers for the success and massive deployment of MPLS at the intra-domain level. Among these features are: Virtual Private Services-MPLS offers a flexible and scalable way to provision and manage Layer 3 Virtual Private Networks (VPNs) [2], together with Layer 2 Virtual Private LAN Services (VPLSs) [3]. Traffic Engineering (TE)-This feature is supported by extensions of the two most widely deployed Interior Gateway Protocols (IGPs), namely OSPF-TE [4] and IS-IS-TE [5], as well as TE extensions of the Resource Reservation Protocol (RSVP) [6]. While the IGP extensions are used to carry information about the state and availability of network resources, such as link bandwidth utilization, or link delays, the RSVP-TE extensions are widely used for signaling purposes. RSVP-TE supplies MPLS networks with valuable TE functionalities including resource reservations, explicit path routing, reroute around a node or a link failure, and preemption of resources along Label Switched Paths (LSPs).
This paper describes a simulation model, developed within the framework of the EuQoS project, whi... more This paper describes a simulation model, developed within the framework of the EuQoS project, which is aimed at assessing QoS on an end-to-end basis, across heterogeneous networks. In that respect, it discusses modelling issues related to access network technologies, to the core network, and to traffic generation. Furthermore, the implementation of the simulator within the ns-2 framework is described, and preliminary simulation results are reported, showing how the lack of QoS mechanisms in one segment of the network negatively affects the overall performance..
33rd European Conference and Exhibition on Optical Communication - ECOC 2007, 2007
This paper proposes a new RWA algorithm that takes into consideration the Maximum Transmission Di... more This paper proposes a new RWA algorithm that takes into consideration the Maximum Transmission Distance (MTD) parameter to be applied to semi-transparent optical networks, achieving a considerable benefit in terms of blocking probability reduction.
2007 9th International Conference on Transparent Optical Networks, 2007
This contribution deals with the RWA (routing and wavelength assignment) in semi-transparent opti... more This contribution deals with the RWA (routing and wavelength assignment) in semi-transparent optical networks. In semi-transparent networks, a parameter called Maximum Transmission Distance (MTD) is used to indicate the distance reachable in wavelength continuity. When for a given lightpath, the signal cannot be detected at the destination node a regenerator has to be installed in an intermediate node. The regenerator breaks up the optical continuity and the optical network becomes a semi-transparent optical network. The new RWA mechanism proposed in this paper will take into account the physical impairment such as the Maximum Transmission Distance (MTD). Moreover this new RWA algorithm will be based on the Prediction-Based Routing (PBR) mechanism and will take into account the routing inaccuracy problem. The goal of the proposed algorithm will be both, to reduce the number of blocked connections due to the routing inaccuracy problem and to select routes that fulfil the MTD physical impairment. On the other hand, transparent optical networks do not convert the signal to the electrical domain in the intermediate nodes but rather keep the signal in the optical domain from source to destination. Full transparency is not however always achievable in long distance networks, due to the degradation an optical signal accumulates in propagation. In semi-transparent optical networks regenerators are employed when the quality of the signal falls below the level required for an acceptably correct detection.
Conference onOptical Network Design and Modeling, 2005., 2005
Inter-Domain Quality of Service (QoS) Routing has become a strong requirement in the present Inte... more Inter-Domain Quality of Service (QoS) Routing has become a strong requirement in the present Internet, and this requirement will also be present in the Next Generation Optical based worldwide network. At present end-to-end QoS Routing (QoSR) represents a complex problem mainly be- cause the de-facto standard Inter-domain routing protocol, namely the Border Gateway Protocol (BGP) has not inbuilt QoSR capabilities.
Abstract���In this paper we propose, design, and test a self-adaptive Traffic Engineering (TE) sc... more Abstract���In this paper we propose, design, and test a self-adaptive Traffic Engineering (TE) scheme for multihomed stub Autonomous Systems (ASes). This scheme is based on a reduced set of self-adaptive and collaborative Smart Routing Managers (SRMs), which are exclusively located at those multihomed stub ASes participating in our scheme. These SRMs are able to improve the end-to-end traffic performance of delay-sensitive applications. In addition, the SRMs significantly contribute to overall network stability based on their ...
In a time when several audio Ethernet networking solutions are being studied and developed, the a... more In a time when several audio Ethernet networking solutions are being studied and developed, the analysis of the latency introduced by theses networks is fundamental. This analysis is the subject of the present paper, and is necessary not only to enable the identification of the factors that can be optimised, but also to support the decision about the possibility or not of the inclusion of in-band synchronism signalling.
Quality of Service Routing is at present an active and remarkable research area, since most emerg... more Quality of Service Routing is at present an active and remarkable research area, since most emerging network services require specialized Quality of Service (QoS) functionalities that cannot be provided by the current QoS-unaware routing protocols. The provisioning of QoS based network services is in general terms an extremely complex problem, and a significant part of this complexity lies in the routing layer. Indeed, the problem of QoS Routing with multiple additive constraints is known to be NP-hard. Thus, a successful and wide deployment of the most novel network services demands that we thoroughly understand the essence of QoS Routing dynamics, and also that the proposed solutions to this complex problem should be indeed feasible and affordable. This article surveys the most important open issues in terms of QoS Routing, and also briefly presents some of the most compelling proposals and ongoing research efforts done both inside and outside the E-Next Community to address some of those issues. q
Abstract���Multihoming in combination with route optimization tools working in short timescales i... more Abstract���Multihoming in combination with route optimization tools working in short timescales is becoming a common practice in order to improve end-to-end QoS at the edge of the Internet. Nevertheless, the stability repercussions of these selfish practices under massive utilization are absolutely unpredictable. Therefore, self-adaptive mechanisms will be inevitable if masses of completely independent and uncoordinated multihomed stub Autonomous Systems are allowed to simultaneously change their interdomain traffic ...
This paper describes and evaluates the performance of a combined intra-and inter-domain routing m... more This paper describes and evaluates the performance of a combined intra-and inter-domain routing model for optical networks. The model is supported by a set of network components called Inter-Domain Routing Agents (IDRAs). Each domain or Autonomous System allocates one or more of these agents, which are the ones responsible for computing and finding constrained inter-domain lightpaths. Each IDRA exchanges with its peers two kinds of information, i.e, reachability information and network state information. In order to provide a highly scalable routing model, the network state information exchanged among the IDRAs is highly aggregated. In this particular work we introduce two opaque additive metrics which are used by the IDRAs to asses: i) the wavelength occupancy across domains; and ii) the resilience capabilities of downstream domains. Aggregating information at the domain boundaries aids in terms of overall scalability, but clearly, the frequency of this information exchange in order to keep the opaque metrics updated, needs to be tightly controlled. Our simulation results show that the opaque-aggregation scheme we are proposing in this paper is robust to the frequency of these updates.
This paper presents a technical overview of VPLS (Virtual Private LAN Service), its current state... more This paper presents a technical overview of VPLS (Virtual Private LAN Service), its current state of the art, its strengths and weaknesses, and most important of all, several open issues and future research work.
This paper describes and evaluates the performance of a combined intra-and inter-domain routing m... more This paper describes and evaluates the performance of a combined intra-and inter-domain routing model for optical networks. The model is supported by a set of network components called Inter-Domain Routing Agents (IDRAs). Each domain or Autonomous System allocates one or more of these agents, which are the ones responsible for computing and finding constrained inter-domain lightpaths. Each IDRA exchanges with its peers two kinds of information, i.e, reachability information and network state information. In order to provide a highly scalable routing model, the network state information exchanged among the IDRAs is highly aggregated. In this particular work we introduce two opaque additive metrics which are used by the IDRAs to asses: i) the wavelength occupancy across domains; and ii) the resilience capabilities of downstream domains. Aggregating information at the domain boundaries aids in terms of overall scalability, but clearly, the frequency of this information exchange in order to keep the opaque metrics updated, needs to be tightly controlled. Our simulation results show that the opaque-aggregation scheme we are proposing in this paper is robust to the frequency of these updates.
We show that a modified version of a path-vector protocol can drastically reduce the blocking and... more We show that a modified version of a path-vector protocol can drastically reduce the blocking and converge significantly faster, while exchanging less number of routing messages both during failure-free conditions and during a convergence.
31st European Conference on Optical Communications (ECOC 2005), 2005
Automatically Switched Optical Networks (ASON) specifications strongly recommends a hierarchical ... more Automatically Switched Optical Networks (ASON) specifications strongly recommends a hierarchical network architecture. In this paper authors propose three hierarchical routing algorithms, aiming to optimize the global network performance, while guaranteeing scalability.
We present a distributed routing algorithm for finding two disjoint (primary and backup) QoS path... more We present a distributed routing algorithm for finding two disjoint (primary and backup) QoS paths that run across multiple domains. Our work is inspired by the recent interest in establishing communication paths with QoS constrains spanning multiple IP/MPLS domains. In such settings, the routing decisions in each domain are made by the Path Computation Element (PCE). We assume that the PCEs run a joint distributed routing protocol, decoupled from the BGP, which enables them to establish efficient paths across multiple domains.
Optical networks provide a clear opportunity to redesign the multi-domain routing paradigm. This ... more Optical networks provide a clear opportunity to redesign the multi-domain routing paradigm. This paper reviews the current limitations in multi-domain routing as well as some of the research lines in the optical area.
Multi-Protocol Label Switching (MPLS) has become the core switching infrastructure at the intra-d... more Multi-Protocol Label Switching (MPLS) has become the core switching infrastructure at the intra-domain level. However, little progress has been made to extend the reach of MPLS Label Switched Paths (LSPs) across domains. Among the problems that remain unsolved is how to efficiently find and establish primary and protection inter-domain LSPs for mission-critical services subject to QoS constraints. In this paper we first review the major limitations impeding the deployment of these kinds of LSPs across multiple domains. Next, we discuss about the advantages of the recently proposed Path Computation Element (PCE)based architecture, and overview how this architecture can be exploited to tackle some of the main limitations exposed. Finally, we report the key features of a distributed routing scheme that we have recently proposed. This distributed routing approach allows a source PCE to count with sufficient information so as to find and establish optimal disjoint QoS paths across multiple domains in an efficient way. [1]. The advantages of MPLS are not confined only to integration and efficient switching of IP packets. Indeed, the available implementations of MPLS offer a suite of value-added features, which have been key drivers for the success and massive deployment of MPLS at the intra-domain level. Among these features are: Virtual Private Services-MPLS offers a flexible and scalable way to provision and manage Layer 3 Virtual Private Networks (VPNs) [2], together with Layer 2 Virtual Private LAN Services (VPLSs) [3]. Traffic Engineering (TE)-This feature is supported by extensions of the two most widely deployed Interior Gateway Protocols (IGPs), namely OSPF-TE [4] and IS-IS-TE [5], as well as TE extensions of the Resource Reservation Protocol (RSVP) [6]. While the IGP extensions are used to carry information about the state and availability of network resources, such as link bandwidth utilization, or link delays, the RSVP-TE extensions are widely used for signaling purposes. RSVP-TE supplies MPLS networks with valuable TE functionalities including resource reservations, explicit path routing, reroute around a node or a link failure, and preemption of resources along Label Switched Paths (LSPs).
This paper describes a simulation model, developed within the framework of the EuQoS project, whi... more This paper describes a simulation model, developed within the framework of the EuQoS project, which is aimed at assessing QoS on an end-to-end basis, across heterogeneous networks. In that respect, it discusses modelling issues related to access network technologies, to the core network, and to traffic generation. Furthermore, the implementation of the simulator within the ns-2 framework is described, and preliminary simulation results are reported, showing how the lack of QoS mechanisms in one segment of the network negatively affects the overall performance..
33rd European Conference and Exhibition on Optical Communication - ECOC 2007, 2007
This paper proposes a new RWA algorithm that takes into consideration the Maximum Transmission Di... more This paper proposes a new RWA algorithm that takes into consideration the Maximum Transmission Distance (MTD) parameter to be applied to semi-transparent optical networks, achieving a considerable benefit in terms of blocking probability reduction.
2007 9th International Conference on Transparent Optical Networks, 2007
This contribution deals with the RWA (routing and wavelength assignment) in semi-transparent opti... more This contribution deals with the RWA (routing and wavelength assignment) in semi-transparent optical networks. In semi-transparent networks, a parameter called Maximum Transmission Distance (MTD) is used to indicate the distance reachable in wavelength continuity. When for a given lightpath, the signal cannot be detected at the destination node a regenerator has to be installed in an intermediate node. The regenerator breaks up the optical continuity and the optical network becomes a semi-transparent optical network. The new RWA mechanism proposed in this paper will take into account the physical impairment such as the Maximum Transmission Distance (MTD). Moreover this new RWA algorithm will be based on the Prediction-Based Routing (PBR) mechanism and will take into account the routing inaccuracy problem. The goal of the proposed algorithm will be both, to reduce the number of blocked connections due to the routing inaccuracy problem and to select routes that fulfil the MTD physical impairment. On the other hand, transparent optical networks do not convert the signal to the electrical domain in the intermediate nodes but rather keep the signal in the optical domain from source to destination. Full transparency is not however always achievable in long distance networks, due to the degradation an optical signal accumulates in propagation. In semi-transparent optical networks regenerators are employed when the quality of the signal falls below the level required for an acceptably correct detection.
Conference onOptical Network Design and Modeling, 2005., 2005
Inter-Domain Quality of Service (QoS) Routing has become a strong requirement in the present Inte... more Inter-Domain Quality of Service (QoS) Routing has become a strong requirement in the present Internet, and this requirement will also be present in the Next Generation Optical based worldwide network. At present end-to-end QoS Routing (QoSR) represents a complex problem mainly be- cause the de-facto standard Inter-domain routing protocol, namely the Border Gateway Protocol (BGP) has not inbuilt QoSR capabilities.
Abstract���In this paper we propose, design, and test a self-adaptive Traffic Engineering (TE) sc... more Abstract���In this paper we propose, design, and test a self-adaptive Traffic Engineering (TE) scheme for multihomed stub Autonomous Systems (ASes). This scheme is based on a reduced set of self-adaptive and collaborative Smart Routing Managers (SRMs), which are exclusively located at those multihomed stub ASes participating in our scheme. These SRMs are able to improve the end-to-end traffic performance of delay-sensitive applications. In addition, the SRMs significantly contribute to overall network stability based on their ...
In a time when several audio Ethernet networking solutions are being studied and developed, the a... more In a time when several audio Ethernet networking solutions are being studied and developed, the analysis of the latency introduced by theses networks is fundamental. This analysis is the subject of the present paper, and is necessary not only to enable the identification of the factors that can be optimised, but also to support the decision about the possibility or not of the inclusion of in-band synchronism signalling.
Quality of Service Routing is at present an active and remarkable research area, since most emerg... more Quality of Service Routing is at present an active and remarkable research area, since most emerging network services require specialized Quality of Service (QoS) functionalities that cannot be provided by the current QoS-unaware routing protocols. The provisioning of QoS based network services is in general terms an extremely complex problem, and a significant part of this complexity lies in the routing layer. Indeed, the problem of QoS Routing with multiple additive constraints is known to be NP-hard. Thus, a successful and wide deployment of the most novel network services demands that we thoroughly understand the essence of QoS Routing dynamics, and also that the proposed solutions to this complex problem should be indeed feasible and affordable. This article surveys the most important open issues in terms of QoS Routing, and also briefly presents some of the most compelling proposals and ongoing research efforts done both inside and outside the E-Next Community to address some of those issues. q
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