Freek Dijkstra

Using RDF to describe networks

Conventions such as iGrid 2005 and SuperComputing show that there is increasing demand for more service options on networks. For such networks, large teams of experts are needed to configure and manage them. In order to make the full potential of hybrid networks available to the ordinary user, the complexity must be reduced.This paper presents the idea of the Network Description Language (NDL), which builds on Semantic Web techniques to create a distributed Topology Knowledge Base (TKB). The TKB can provide a collection of reachability graphs, showing connectivity rules among physical and/or virtual entities.Latching onto the Semantic Web provides network management with a new breed of tools--bots, compilers, browsers, both commercial off-the-shelf (COTS) and open source. The approach appears to be applicable to the Global Lambda Integrated Facility (GLIF) as well as other experimental communities.

A distributed topology information system for optical networks based on the semantic web

The research networking community has embraced novel network architectures to provide e-Science applications with dedicated connections instead of shared links. IP and optical services converge in these new infrastructures to form hybrid networks. Lightpaths are the services offered to clients in the optical portion of the network. They are chosen because they guarantee the appropriate QoS in terms of bandwidth and latency. NDL-the Network Description Language-is a data model offering users and providers of lightpaths with a common ontology to describe topology information of hybrid optical networks. The strength of NDL is that it supports a wide range of applications, including pathfinding, visualisation and asset management, via the definition of a common data model to exchange network descriptions. Since NDL is based on the Semantic Web techniques, it is straightforward to relate NDL with application-specific ontologies. In this paper we present the current status of the NDL schemas and its use in several applications.

Path selection in multi-layer networks

Multi-layer networks are computer networks where the configuration of the network can be changed dynamically at multiple layers. However, in practice, technologies at different layers may be incompatible to each other, which necessitates a careful choice of a multi-layer network model. Not much work has been done on path selection in multi-layer networks. In this paper, we describe how to represent a multi-layer network and we provide algorithms for selecting paths in them. Throughout the paper we will use examples drawn from practical experience with routing in hybrid optical networks.

A multi-layer network model based on ITU-T G.805

In recent years, dynamic multi-layer networks have emerged. Unlike regular networks these multi-layer networks allow users and other networks to interface on different technology layers. While path finding on a single layer is currently well understood, path finding on multi-layer networks is far from trivial. Even the constraints (the possible incompatibilities) are not always clear. This paper proposes a model for multi-layer circuit-switched computer networks, based on ITU-T G.805 and GMPLS standards. Furthermore, it defines a simple algebra that can be used to verify the validity of network connections through such networks. The most important contribution of our model and algebra is that they are technology independent: they can describe any circuit-switched network technology without modifications or tuning to the model and algebra. The model and algebra have been implemented in a syntax and network tool, which are briefly discussed.

A path finding implementation for multi-layer networks

The goal of the OptIPuter project is to tightly couple research applications with dynamically allocated paths. Since OptIPuter is a multi-disciplinary project, the paths through the network often span multiple network domains, and the applications are challenged to find valid network connections through these domains. The challenge arises if the different network domains use different technologies. In this case, we have a multi-layer path finding problem. We will show that there are situations where algorithms as used in single layer networks, such as BGP, SS7 and OSPF-TE, cannot find the shortest path. A shortest path in a multi-layer network can contain loops, and a segment of a shortest path may not be a shortest path in itself. To solve this problem, both a multi-layer network representation as well as new path finding algorithms need to be developed. An additional challenge is to make a generic path finding algorithm that is technology-independent, and does not need to be modified as new technologies emerge. We show that it is possible to create solutions for all three problems. Using RDF-based techniques, we model multi-layer networks and describe incompatibilities for the path finding algorithm in technology-independent way. We also present a path finding algorithm that is able to use this information to find valid paths.

Native 10Gigabit Ethernet experiments over long distances

The current solutions for transmitting data over Wide Area Networks (WANs) are expensive and require protocol translation at layer 1. The IEEE recently standardized the 10Gigabit Ethernet (10GE) WAN PHY as a native gateway from the Local Area Networks (LAN) to the WAN. This opened a debate as to whether Ethernet is now a valid alternative to Synchronous Optical Network/Synchronous Digital Hierarchy (SONET/SDH) for WANs. In this article, we report on the experience gathered while building the first trans-European native 10Gigabit Ethernet testbed based on WAN PHY. We describe and analyze network tests with a 1700km Ethernet network. Our work validates this approach and indicates that Ethernet can offer a large bandwidth to long-distance bulk data transfers at a trans-European level.

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.

Semantics for hybrid networks using the network description language

Several research networks around the world are implementing hybrid networks, that provide end-users with traditional routed IP together with lightpaths. These paths are dynamically configured at user request and network provisioning systems must have topology information, both intra- and inter-domain.We developed the Network Description Language (NDL), based on RDF, a semantic web technique. This language can be used to describe hybrid networks, so that different administrative domains can share and correlate topology information. It supports the end-user to express a lightpath reservation request, and helps the service provider to validate the feasibility of requests. It facilitates generation and exchange of network maps by allowing automatic correlation of information across domains.Our first application ground is GLIF, a collaboration promoting co-operation for Lambda Networking. Several tools for automatic provisioning are in development. However, these tools lack a common network description, which NDL can provide.

Using zero configuration technology for IP addressing in optical networks

Host configuration in optical networks is usually done by hand. In this paper we propose to use zero configuration techniques, including self-assigned IP addresses and multicast DNS to do this automatically. The proposed technology is designed for small networks without central control, and can be applied to optical private networks as long as there is no router in between the end-hosts.