Dimitri Staessens

Research Directions in Network Service Chaining

Network Service Chaining (NSC) is a service deployment concept that promises increased flexibility and cost efficiency for future carrier networks. NSC has received considerable attention in the standardization and research communities lately. However, NSC is largely undefined in the peer-reviewed literature. In fact, a literature review reveals that the role of NSC enabling technologies is up for discussion, and so are the key research challenges lying ahead. This paper addresses these topics by motivating our research interest towards advanced dynamic NSC and detailing the main aspects to be considered in the context of carrier-grade telecommunication networks. We present design considerations and system requirements alongside use cases that illustrate the advantages of adopting NSC. We detail prominent research challenges during the typical lifecycle of a network service chain in an operational telecommunications network, including service chain description, programming, deployment, and debugging, and summarize our security considerations. We conclude this paper with an outlook on future work in this area.

OpenFlow: Meeting carrier-grade recovery requirements

OpenFlow, initially launched as a technology-enabling network and application experimentation in a campus network, has a disruptive potential in designing a flexible network, fostering innovation, reducing complexity and delivering the right economics. This paper focuses on fault tolerance of OpenFlow to deploy it in carrier-grade networks. The carrier-grade network has a strict requirement that the network should recover from the failure within a 50ms interval. We apply two well-known recovery mechanisms to OpenFlow networks: restoration and protection, and run extensive emulation experiments. In OpenFlow, the controlling software is moved to one or more hardware modules (controllers) which can control many switches. For fast failure recovery, the controller must notify all the affected switches about the recovery action within ms interval. This leads to a significant load on the controller. We show that OpenFlow may not be able to achieve failure recovery within a 50ms interval in this situation. We add the recovery action in the switches themselves so that the switches can do recovery without contacting the controller. We show that this approach can achieve recovery within 50ms in a large-scale network serving many flows.

Enabling fast failure recovery in OpenFlow networks

OpenFlow is a novel technology designed at Stanford University which aims at decoupling the controller software from the forwarding hardware of a router or switch. The OpenFlow concept is based on the approach that the forwarding information base (FIB) of a switch can be programmed via a controller which resides at a separate hardware. The goal is to provide a standardized open management interface to the forwarding hardware of a router or switch. The aim of a project SPARC “SPlit ARchitecture Carrier grade networks” is to deploy OpenFlow in carrier grade networks. Reliability is a major issue to deploy OpenFlow in this networks. This work proposes the addition of a fast restoration mechanism in OpenFlow and evaluates the performance by comparing the switchover time and packet loss to existing restoration options in a current OpenFlow implementation.

Software defined networking: Meeting carrier grade requirements

Software Defined Networking is a networking paradigm which allows network operators to manage networking elements using software running on an external server. This is accomplished by a split in the architecture between the forwarding element and the control element. Two technologies which allow this split for packet networks are For CES and Openflow. We present energy efficiency and resilience aspects of carrier grade networks which can be met by Openflow. We implement flow restoration and run extensive experiments in an emulated carrier grade network. We show that Openflow can restore traffic quite fast, but its dependency on a centralized controller means that it will be hard to achieve 50 ms restoration in large networks serving many flows. In order to achieve 50 ms recovery, protection will be required in carrier grade networks.

Recovery in multilayer optical networks

The integration of different network technologies into a multilayer network, as in Internet-based networks carried by optical transport networks (OTNs), creates new opportunities but also challenges with respect to network survivability. In different network layers, recovery mechanisms that are active can be exploited jointly to reach a more efficient or faster recovery from failures. This interworking is also indispensable in order to overcome the variety of failure scenarios that can occur in the multilayer-network environment. A well-considered coordination between the different layers and their recovery mechanisms is crucial in order to attain high performance recovery. This paper provides an overview of multilayer recovery issues and solutions in an Internet protocol (IP)-over-optical-network environment, which is illustrated by quantitative case studies.

A dynamic impairment-aware networking solution for transparent mesh optical networks

Core networks of the future will have a translucent and eventually transparent optical structure. Ultra-high-speed end-to-end connectivity with high quality of service and high reliability will be realized through the exploitation of optimized protocols and lightpath routing algorithms. These algorithms will complement a flexible control and management plane integrated in the proposed solution. Physical layer impairments and optical performance are monitored and incorporated in impairment-aware lightpath routing algorithms. These algorithms will be integrated into a novel dynamic network planning tool that will consider dynamic traffic characteristics, a reconfigurable optical layer, and varying physical impairment and component characteristics. The network planning tool along with extended control planes will make it possible to realize the vision of optical transparency. This article presents a novel framework that addresses dynamic cross-layer network planning and optimization while considering the development of a future transport network infrastructure.

Enabling high availability over multiple optical networks

Carriers are gradually adopting a network model that consists of MPLS-capable routers and OXCs interconnected by high bandwidth WDM links for transporting IP and Ethernet traffic. A control plane can be used to deliver dynamic circuit provisioning in the transport layer, as well as bandwidth provisioning and traffic engineering in higher layers. Globalization drives the quest for end-to-end QoS guarantees over different carrier networks. Recovery mechanisms are crucial to reach the high availability requirements of critical services. In this article, we share our vision on how to enable high availability services, spanning multiple networks using failure protection techniques while complying with administrative constraints.

The QueuePusher: Enabling Queue Management in OpenFlow

The evolution of Software-Defined Networking and the overall acceptance of protocols such as OpenFlow, demonstrates the added value of decoupling the data plane from the control plane. Existing SDN Controllers enable the expected flexibility from such networks by dynamically providing a fine-grained control of each flow. However, hardware-specific configurations, such as the creation of queues or other mechanisms is out of the scope of these controllers. This work presents an extension to a well known OpenFlow controller (Floodlight) to efficiently handle the management of Traffic Control Queues in OpenFlow switches, resorting to a RESTful northbound interface. The obtained results demonstrate further possibility of developing innovative on-demand resource reservation mechanisms in SDN without adding unbearable overheads.

A Demonstration of Fast Failure Recovery in Software Defined Networking

Software defined networking (SDN) is a recent architectural framework for networking, which aims at decoupling the network control plane from the physical topology and at having the forwarding element controlled through a uniform vendor-agnostic interface. A well-known implementation of SDN is OpenFlow. The core idea of OpenFlow is to provide direct programming of a router or switch to monitor and modify the way in which the individual packets are handled by the device. We describe our implemented fast failure recovery mechanisms (Restoration and Protection) in OpenFlow, capable of recovering from a link failure using an alternative path. In the demonstration, a video clip is streamed from a server to a remote client, which is connected by a network with an emulated German Backbone Network topology. We show switching of the video stream from the faulty path to the fault-free alternative path (restored or protected path) upon failure.

Automatic bootstrapping of OpenFlow networks

OpenFlow decouples the control plane functionality from switches, and embeds it into one or more servers called controllers. One of the challenges of OpenFlow is to deploy a network where control and data traffic are transmitted on the same channel (in-band mode). Implementing such an in-band mode is complex, since switches have to search and establish a path to the controller (bootstrapping) through the other switches in the network. In this paper, we propose a method that facilitates this automatic bootstrapping of switches. In this method, the controller establishes its own control network through the neighbor switches that are connected to it by the OpenFlow protocol. We measure suitability of the proposed method by performing bootstrapping experiments in different types of topologies: linear, ring, star and mesh topologies. The experimental results show that the proposed method allows bootstrapping in a minimal time, which makes it suitable even for a large network.