Multi-domain Optical Networks Research Articles

OBGP+: An improved path-vector protocol for multi-domain optical networks

One of the essential components for the dynamic provisioning of lightpaths across multiple domains is the Routing and Wavelength Assignment (RWA) strategy adopted. The consolidation that path-vector protocols have had in practice, has motivated the optical extension to BGP (OBGP). We claim, however, that a routing model mostly centered on the exchange of reachability information–like the one we have today with BGP or the one offered by OBGP–will not be sufficient for multi-domain optical networks. Routing domains must be able to exchange both reachability as well as aggregated Path-State Information (PSI). Understanding that this is a missing piece in the routing models provided by BGP and OBGP is easy nowadays, but contributing with solutions capable of highly improving the performance of a path-vector without impacting on key aspects of the protocol–fundamentally, its scalability, its convergence properties, and the number of routing messages exchanged between domains–is a challenging task. In this paper we propose OBGP +, which is a very simple extension of a path-vector protocol supporting the computation and advertisement of PSI between optical domains. The PSI that we propose to use is highly condensed in the form of a single integer value. In order to avoid the typical increase in the number of routing messages associated with the update of PSI, we propose to piggy-back the updates in non-dummy Keepalive messages exchanged between OBGP+ neighbors. Extensive simulations reveal that, despite its simplicity: (i) OBGP+ is able to drastically reduce the blocking experienced with a path-vector protocol like OBGP; (ii) OBGP+ needs much less number of routing messages than OBGP to achieve such performance; and (iii) the convergence and restoration features of OBGP+ are also better than those of OBGP, which is particularly important for connections that lack a protection path.

P-cycle Protection in multi-domain optical networks

Providing resilient inter-domain connections in multi-domain optical GMPLS networks is a challenge. On the one hand, the integration of different GMPLS domains to run traffic engineering operations requires the development of a framework for inter-domain routing and control of connections, while keeping the internal structure and available resources of the domains undisclosed to the other operators. On the other hand, the definition of mechanisms to take advantage of such automatically switched inter-domain connectivity is still an open issue. This article focuses on the analysis of applicability of one of these mechanisms: P-cycle-based protection. The proposed solution is based on the decomposition of the multi-domain resilience problem into two sub-problems, namely, the higher level inter-domain protection and the lower level intra-domain protection. Building a P-cycle at the higher level is accomplished by certain tasks at the lower level, including straddling link connection, capacity allocation and path selection. In this article, we present several methods to realize inter-domain P-cycle protection at both levels and we evaluate their performance in terms of availability and spent resources. A discussion on a proposal of implementation of signalling based on extensions of existing protocols such as RSVP-TE and the PCE architecture illustrates the practical viability of the approach.

Multi-domain lightpath authorization, using tokens

This paper highlights the concepts and results of our research, leading to demonstrations during the period 2005–2007 to develop a flexible and simple access control model, and corresponding support tools to provision multi-domain optical network resources on demand. We introduce the general network resources provisioning model that extends the Generic AAA Authorisation sequences for multi-domain scenarios, and explain how token based access control and policy enforcement can be used during the provisioned resource access. To build a solid conceptual foundation for the proposed token, based access control, the paper revisits existing token definition and proposes a new definition in the context of our research. We subsequently show the use of tokens during different stages of the lightpath provisioning process. The paper identifies and describes two major scenarios in multidomain lightpath provisioning: the chain and tree approaches. The proposed token concept allows a simple combination of access control enforcement at different networking layers: the packet layer, the path layer, and the service layer. We end with a brief description of a few demonstrations that proves the proposed concepts and illustrates its acceptance by a wider networking community.

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.

New insights on survivability in multi-domain optical networks

With the development of intelligent optical networks and the general multi-protocol label switching (GMPLS) technique, the seamless convergence between IP network and optical network is no longer be a dream but a practical reality. Similar to the Internet, current optical networks have been divided into multiple domains each of which has its own network provider and management policy. Therefore, the development of multi-domain optical networks will be the trend of new-generation intelligent optical networks, and GMPLS-based survivability for multi-domain optical networks will become a hot topic of research in the future. This paper provides a comprehensive review of the existing survivable schemes in multi-domain optical networks and analyzes the shortcomings of current research. Based on previous studies, we present possible challenges and propose new ideas to design efficient survivable schemes to guide the future work of researchers in multi-domain optical networks.

LSSP: A novel local segment-shared protection for multi-domain optical mesh networks

This paper investigates the survivability in multi-domain optical mesh networks and presents a new model of multiple failures that is defined that there is one failed link in each single-domain and are multiple failed links in the whole multi-domains. Since the conventional Extended-Path-Shared Protection (EPSP) approach cannot provide 100% protection ability for this model, we propose a novel approach called Local Segment-Shared Protection (LSSP) to provide efficient survivability for this model. In our approach, LSPP first computes one inter-domain primary path for each connection request and follows to compute one intra-domain link-disjoint local segment-backup path for each primary-segment path in each single-domain, respectively, where the backup resources can be shared by different segment-backup paths if the corresponding primary-segment paths are link-disjoint. Compared with the conventional EPSP, although LSSP increases moderate backup resources consumption, it not only can provide 100% protection ability for multiple failures but also can perform much faster recovery time and easier survivable operation and management. The simulation results are shown to be promising.

Hierarchical routing in multi-domain optical networks

Given the increasing adoption of DWDM networking technology, there is now a growing need to address distributed inter-domain lightpath provisioning issues. Although inter-domain provisioning has been well studied for packet/cell-switching networks, the wavelength dimension presents many additional challenges. To address this challenge, a detailed hierarchical routing GMPLS-based framework for provisioning all-optical and opto-electronic multi-domain DWDM networks is presented. The scheme adapts various topology abstraction schemes to improve routing scalability and lower inter-domain blocking probabilities. Related inter-domain lightpath RWA and signaling schemes are also tabled. Performance analysis results are also presented to demonstrate the effectiveness of the proposed mechanisms along with directions for future research work.

Approach to reduce optical routing instability in multidomain mesh networks

How to reduce the interdomain routing instability in multidomain optical networks is a burning issue of the day. An approach called active choke of interdomain routing (ACIR) is proposed to decrease the instability caused by temporary node overload. In this approach, when the network load increases to a certain value, the traffic requests without a minimum number of spanned domains are rejected directly or with a fixed or floating probability, while the rest are accepted. With the wavelength continuity constraint, numerical results on two network topologies demonstrate that the ACIR approach provides better blocking performance during heavy traffic and lower load at both nodes and domain controllers.

Dynamic routing for shared path protection in multidomain optical mesh networks

The routing problem for shared path protection in multidomain optical mesh networks is more difficult than that in single-domain mesh networks due to the lack of complete and global knowledge of the network topology and bandwidth allocation. To overcome this difficulty, we propose an aggregated network modeling by underestimation with a two-step routing strategy. In the first step, a rough routing solution is sketched in a virtual network that is the topology aggregation of the multidomain network. A complete routing is then determined by solving routing problems within the original single-domain networks. The first step can be solved by either using an exact mathematical program or a heuristic, whereas the second step is always solved by heuristics. Computational results show the relevance of the aggregated network modeling. They also prove the scalability of the proposed routing for multidomain networks and its efficiency in comparison with the optimal solution obtained by use of the complete information scenario. In addition, we believe that short working paths lead to a higher possibility of sharing backup resources between backup paths. Our mathematical program model minimizes the total requested resources and at the same time provides a short working path, resulting in a further overall saving of resources.

Dynamic paths in multi-domain optical networks for grids

Many Grid applications require high bandwidth end-to-end connections between Grid resources in different domains. Fiber optic networks, owned by different providers, have to cooperate in a coordinated manner in order to provide an end-to-end connection. Currently, multi-domain optical network solutions require paper-based long-term contracts between administrative domains. This paper describes a solution for dynamically creating optical connections between different autonomous domains. This was implemented in the form of a Grid Service following the Open Grid Service Architecture. In our prototype, each switch belongs to a different network domain. Our Grid Service uses a toolkit based on the Generic Authorization, Authentication, and Accounting framework. This toolkit authorizes the use of optical infrastructure elements based on specific policies that are active within each domain. To complete our multi-domain authorization architecture, a Broker Service was also implemented. Our Broker Service interacts with the Grid Service instances to provide Grid application with a simplified way to set up end-to-end connections on demand.

Interdomain dynamic wavelength routing in the next-generation translucent optical Internet

Feature Issue on Next-Generation WDM Network Design and Routing (WDMN). Future home and enterprise Internet users need high-bandwidth end-to-end connections that have to be provisioned automatically and dynamically. We need to make optical-layer routing as scalable and flexible as IP routing in today's Internet to support high-end applications. We study the problem of interdomain dynamic wavelength routing based on a multidomain translucent optical network model, which allows end-to-end lightpaths to be set up not only across multiple routing domains but also through two network layers: the optical layer and the regeneration layer. In this model, a lightpath can traverse the domain boundary either through optical bypass (OOO) or through optical-electrical-optical regeneration (OEO). We propose an interdomain dynamic wavelength-routing scheme with modest computational complexity to address the problem from an algorithmic perspective. Our experimental results show that the proposed interdomain dynamic wavelength-routing scheme can (a) flexibly incorporate various cost metrics and local (or intradomain) routing schemes into a uniform interdomain routing framework, (b) effectively set up end-to-end lightpaths in a multidomain translucent network, and (c) efficiently use both optical- and regeneration-layer resources.