79,161 research outputs found
Concepts and mechanisms for consistent route transitions in software-defined networks
Software-defined Networking (SDN) [1] is a big trend in network research and industry. The key idea of SDN is to separate the control and the forwarding functionality. In conventional networks the firmware on the switches determines how the switches handle packets, so that they treat all packets in exactly the same way. This leads to static networks, that can not adapt to changing requirements. In Software-defined Networks a (logically) centralized controller enables the network administration to change the routing simply by updating the controller. The controller then can change the flow table entries of a subset or even all the switches in the network. There is no longer the need to update every switch separately. SDN is in general used for highly adaptive routing to fit the requirements of dynamic load, frequent topology changes, migration of virtual machines and hosts. This work is about consistent route updates in Software-defined Networks. Two classes of consistency have to be distinguished. The first one is eventual consistency, that means during the update inconsistency's can occur, but the final state will be consistent. The second one is strict consistency, here the routes are always consistent, even during the update process. Inconsistent updates can lead to security issues, loss of connection, inaccessibility and many other problems. In current networks updates are necessary to fit the frequently changing requirements. The problem with (strict) consistent updates in SDN is that there are no atomic updates because the switches are inherently distributed. And even if there would be such an update, it would affect packets in transit. Therefore the goal is to avoid transient route inconsistencies like “black holes” and loops. There are already a couple of update strategies for SDN which result in consistent updates, but all of them are limited in some way, for example some can just be used for OSPF or BGP. There is also one approach by Reitblatt et al. [3], that is not limited. This strategy is a two phase update which leads to a “per packet consistency”. The old route and the new route are installed at the same time, so that every packet is on a consistent route (the old route, before the update, or the new one, after the update). This approach has an overhead in terms of storage-use, because the new route exists at the same time as the old one and also needs rewriting of the packet headers to signal the phase. But the storage capacity of switches is limited and so a doubling of forwarding table space is a high burden. The approach shown in this work is more light-weight and requires no change of header fields and no additional forwarding table space or any other modifications of the switches
Timed Consistent Network Updates
Network updates such as policy and routing changes occur frequently in
Software Defined Networks (SDN). Updates should be performed consistently,
preventing temporary disruptions, and should require as little overhead as
possible. Scalability is increasingly becoming an essential requirement in SDN.
In this paper we propose to use time-triggered network updates to achieve
consistent updates. Our proposed solution requires lower overhead than existing
update approaches, without compromising the consistency during the update. We
demonstrate that accurate time enables far more scalable consistent updates in
SDN than previously available. In addition, it provides the SDN programmer with
fine-grained control over the tradeoff between consistency and scalability.Comment: This technical report is an extended version of the paper "Timed
Consistent Network Updates", which was accepted to the ACM SIGCOMM Symposium
on SDN Research (SOSR) '15, Santa Clara, CA, US, June 201
Fast network configuration in Software Defined Networking
Software Defined Networking (SDN) provides a framework to dynamically adjust and re-program the data plane with the use of flow rules. The realization of highly adaptive SDNs with the ability to respond to changing demands or recover after a network failure in a short period of time, hinges on efficient updates of flow rules. We model the time to deploy a set of flow rules by the update time at the bottleneck switch, and formulate the problem of selecting paths to minimize the deployment time under feasibility constraints as a mixed integer linear program (MILP). To reduce the computation time of determining flow rules, we propose efficient heuristics designed to approximate the minimum-deployment-time solution by relaxing the MILP or selecting the paths sequentially. Through extensive simulations we show that our algorithms outperform current, shortest path based solutions by reducing the total network configuration time up to 55% while having similar packet loss, in the considered scenarios. We also demonstrate that in a networked environment with a certain fraction of failed links, our algorithms are able to reduce the average time to reestablish disrupted flows by 40%
DISCO: Distributed Multi-domain SDN Controllers
Modern multi-domain networks now span over datacenter networks, enterprise
networks, customer sites and mobile entities. Such networks are critical and,
thus, must be resilient, scalable and easily extensible. The emergence of
Software-Defined Networking (SDN) protocols, which enables to decouple the data
plane from the control plane and dynamically program the network, opens up new
ways to architect such networks. In this paper, we propose DISCO, an open and
extensible DIstributed SDN COntrol plane able to cope with the distributed and
heterogeneous nature of modern overlay networks and wide area networks. DISCO
controllers manage their own network domain and communicate with each others to
provide end-to-end network services. This communication is based on a unique
lightweight and highly manageable control channel used by agents to
self-adaptively share aggregated network-wide information. We implemented DISCO
on top of the Floodlight OpenFlow controller and the AMQP protocol. We
demonstrated how DISCO's control plane dynamically adapts to heterogeneous
network topologies while being resilient enough to survive to disruptions and
attacks and providing classic functionalities such as end-point migration and
network-wide traffic engineering. The experimentation results we present are
organized around three use cases: inter-domain topology disruption, end-to-end
priority service request and virtual machine migration
Adaptive Robust Traffic Engineering in Software Defined Networks
One of the key advantages of Software-Defined Networks (SDN) is the
opportunity to integrate traffic engineering modules able to optimize network
configuration according to traffic. Ideally, network should be dynamically
reconfigured as traffic evolves, so as to achieve remarkable gains in the
efficient use of resources with respect to traditional static approaches.
Unfortunately, reconfigurations cannot be too frequent due to a number of
reasons related to route stability, forwarding rules instantiation, individual
flows dynamics, traffic monitoring overhead, etc.
In this paper, we focus on the fundamental problem of deciding whether, when
and how to reconfigure the network during traffic evolution. We propose a new
approach to cluster relevant points in the multi-dimensional traffic space
taking into account similarities in optimal routing and not only in traffic
values. Moreover, to provide more flexibility to the online decisions on when
applying a reconfiguration, we allow some overlap between clusters that can
guarantee a good-quality routing regardless of the transition instant.
We compare our algorithm with state-of-the-art approaches in realistic
network scenarios. Results show that our method significantly reduces the
number of reconfigurations with a negligible deviation of the network
performance with respect to the continuous update of the network configuration.Comment: 10 pages, 8 figures, submitted to IFIP Networking 201
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Don't mind the gap: Bridging network-wide objectives and device-level configurations
We reflect on the historical context that lead to Propane, a high-level language and compiler to help network operators bridge the gap between network-wide routing objectives and low-level configurations of devices that run complex, distributed protocols. We also highlight the primary contributions that Propane made to the networking literature and describe ongoing challenges. We conclude with an important lesson learned from the experience
Evolving SDN for Low-Power IoT Networks
Software Defined Networking (SDN) offers a flexible and scalable architecture
that abstracts decision making away from individual devices and provides a
programmable network platform. However, implementing a centralized SDN
architecture within the constraints of a low-power wireless network faces
considerable challenges. Not only is controller traffic subject to jitter due
to unreliable links and network contention, but the overhead generated by SDN
can severely affect the performance of other traffic. This paper addresses the
challenge of bringing high-overhead SDN architecture to IEEE 802.15.4 networks.
We explore how traditional SDN needs to evolve in order to overcome the
constraints of low-power wireless networks, and discuss protocol and
architectural optimizations necessary to reduce SDN control overhead - the main
barrier to successful implementation. We argue that interoperability with the
existing protocol stack is necessary to provide a platform for controller
discovery and coexistence with legacy networks. We consequently introduce
{\mu}SDN, a lightweight SDN framework for Contiki, with both IPv6 and
underlying routing protocol interoperability, as well as optimizing a number of
elements within the SDN architecture to reduce control overhead to practical
levels. We evaluate {\mu}SDN in terms of latency, energy, and packet delivery.
Through this evaluation we show how the cost of SDN control overhead (both
bootstrapping and management) can be reduced to a point where comparable
performance and scalability is achieved against an IEEE 802.15.4-2012 RPL-based
network. Additionally, we demonstrate {\mu}SDN through simulation: providing a
use-case where the SDN configurability can be used to provide Quality of
Service (QoS) for critical network flows experiencing interference, and we
achieve considerable reductions in delay and jitter in comparison to a scenario
without SDN
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