Sergio Sánchez-López

Quality of Service Routing

Constraint-based routing is an invaluable part of a full- fledged Quality of Service architecture. Unfortunately, QoS routing with multiple additive constraints is known to be a NP-complete problem. Hence, accurate constraint-based routing algorithms with a fast running time are scarce, perhaps even non-existent. The need for such algorithms has resulted in the proposal of numerous heuristics and a few exact solutions.

A hierarchical routing approach for GMPLS based control plane for ASON

A hierarchical network architecture is one of the hard recommendations stated at the automatically switched optical networks (ASON) specifications. This paper focuses on providing ASON with a hierarchical routing in order to ensure the scalability for large worldwide networks, mainly focusing on the functionality expected from GMPLS routing, such as aggregation schemes and routing algorithms, targeting to optimize the global network performance while guaranteeing scalability. Simulation results indeed show the benefits obtained owing to harder overhead reduction without impacting on the blocking probability.

Toward a new route control model for multidomain optical networks

The design of the control plane model for multidomain optical networks poses complex challenges and introduces many open problems. Some initiatives have proposed optical BGP (OBGP), which is an extension of BGP supporting the advertisement and signaling of optical information between routing domains. We argue, however, that future optical networks offer the opportunity to avoid inheriting the limitations of BGP, especially in terms of routing and traffic engineering control. In this article we present a route control model replacing BGP/OBGP. Extensive simulations confirm that our route control model is able to drastically reduce the blocking experienced with OBGP, and this can be accomplished without increasing the number or frequency of routing updates exchanged between domains.

Routing and wavelength assignment under inaccurate routing information in networks with sparse and limited wavelength conversion

In large dynamic networks it is extremely difficult to maintain accurate routing information on all network nodes. Different causes can motivate this inaccuracy, such as the state aggregation produced in hierarchical networks, the delay in flooding the network state, and the triggering policy used to determine when this network state information must be updated. This paper focuses on the inaccuracy caused by the triggering policies. Triggering policies are included in the routing protocol to reduce the large number of update messages needed to guarantee accurate network state information on all the network nodes. The BYPASS based optical routing (BBOR) has already been proposed by the authors to reduce the effects of having inaccurate routing information in networks operating under the wavelength-continuity constraint This paper extends the BBOR mechanism to be applied to wavelength convertible networks and evaluates its performance.

Hierarchical Routing with QoS Constraints in Optical Transport Networks

Optical Transport Networks (OTN) with automatical switching capabilities are named ASON. Hierarchical routing is required in the ASON recommendations to achieve scalability. Basically, hierarchical routing consists of three main components, an aggregation scheme, an update policy and a routing algorithm. This paper proposes a new network structure focusing on these three components. We propose a new aggregation scheme; an update policy based on a threshold value; and we also extend an already proposed routing mechanism to be applied to a hierarchical network. Main skill of this routing mechanism is to reduce the connection blocking increase because of selecting paths based on inaccurate routing information. This inaccuracy is introduced both by the aggregation process and by the update policy.

PNNI-based control plane for automatically switched optical networks

Much effort has been spent on the definition of control plane protocols for automatically switched optical networks (ASON). Most of the proposals brought into the standardization for an International Telecommunications Union-Telecommunication Sector, Internet Engineering Task Force, and Optical Internetworking Forum are based on Internet protocol concepts. One such proposal is the generalized multi-protocol label switching (GMPLS), an extension of the MPLS traffic engineering control plane model that includes nonpacket switched technologies (time, wavelength, and fiber switching). Recently, the potential use of private network-network interface (PNNI) in ASONs has been discussed as an alternative proposal by the standardization bodies. The goal of this paper is to appropriately adapt asynchronous transfer mode into an optical PNNI (O-PNNI) protocol that can be used as the control plane of ASONs. The paper also provides a critical viewpoint on the potential usage of either O-PNNI or GMPLS control plane and analyzes the pros and cons of each. The methodology adopted toward devising O-PNNI hinges on reviewing PNNI along with ASON recommendations in order to determine the set of PNNI features that require adaptation. Having identified these features we engineer and present appropriate solutions relating to routing, signaling and addressing aspects.

A hierarchical routing approach for optical transport networks

Although the automatically switched optical networks (ASON) specifications strongly recommend a hierarchical network architecture for these networks, this is still an open issue. The hierarchical network concept involves several mechanisms mainly related with signaling and routing, such as the aggregation scheme, the dissemination process, the updating policy and the routing algorithms. The existing mechanisms for flat networks must be substantially modified to be applied to a hierarchical network architecture. In this paper, authors propose a complete hierarchical routing approach mainly focusing on routing concerns, aiming to optimize the global network performance while guaranteeing scalability.

A combined intra-domain and inter-domain QoS routing model for optical networks

� Abstract—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 because the de-facto standard Inter-domain routing protocol, namely the Border Gateway Protocol (BGP) has not inbuilt QoSR capabilities. Moreover, BGP entirely obscures the availability of Intra-Domain resources in any transit domain within an end-to-end Inter-Domain path, which shifts any tentative proposal to cope with the issue of Inter-Domain QoSR even farther from optimality. Given that Inter-Domain routing in Optical Networks is an active research area in this moment, it seems wise to address the issue of QoSR provisioning from its very foundations. Thus, in this paper we introduce a Combined Intra-Domain and Inter-Domain QoSR Model for Optical Networks. Our goal is to provide a highly efficient coupling between both routing schemes with the aim that the combined QoSR model could be able to supply multiconstrained end-to-end optical paths closer to optimality.

A Proposal for Inter-domain QoS Routing Based on Distributed Overlay Entities and QBGP

This paper proposes a novel and incremental approach to Inter-Domain QoS Routing. Our approach is to provide a completely distributed Overlay Architecture and a routing layer for dynamic QoS provisioning, and to use QoS extensions and Traffic Engineering capabilities of the underlying BGP layer for static QoS provisioning. Our focus is mainly on influencing how traffic is exchanged among non-directly connected multi-homed Autonomous Systems based on specific QoS parameters. We provide evidence supporting the feasibility of our approach by means of simulation.

A QoS Routing Mechanism for Reducing the Routing Inaccuracy Effects

In highly dynamic large IP/MPLS networks, when routing information includes not only topology information but also information to provide QoS, such as available link bandwidth, network state databases must be frequently updated. This updating process generates an important signaling overhead. Reducing this overhead implies having inaccurate routing information, which may cause both non-optimal path selection and a call-blocking increase. In order to avoid both effects in this paper we suggest a new QoS explicit routing mechanism called BYPASS Based Routing (BBR), which is based on bypassing those links along the selected path that potentially cannot cope with the traffic requirements. Routing algorithms derived from the proposed BBR mechanism reduce the call-blocking ratio without increasing the amount of routing control information.