Levente Csikor

ESCAPE: extensible service chain prototyping environment using mininet, click, NETCONF and POX

Mininet is a great prototyping tool which combines existing SDN-related software components (e.g., Open vSwitch, OpenFlow controllers, network namespaces, cgroups) into a framework, which can automatically set up and configure customized OpenFlow testbeds scaling up to hundreds of nodes. Standing on the shoulders of Mininet, we implement a similar prototyping system called ESCAPE, which can be used to develop and test various components of the service chaining architecture. Our framework incorporates Click for implementing Virtual Network Functions (VNF), NETCONF for managing Click-based VNFs and POX for taking care of traffic steering. We also add our extensible Orchestrator module, which can accommodate mapping algorithms from abstract service descriptions to deployed and running service chains.

SDN based testbeds for evaluating and promoting multipath TCP

Multipath TCP is an experimental transport protocol with remarkable recent past and non-negligible future potential. It has been standardized recently, however the evaluation studies focus only on a limited set of isolated use-cases and a comprehensive analysis or a feasible path of Internet-wide adoption is still missing. This is mostly because in the current networking practice it is unusual to configure multiple paths between the endpoints of a connection. Therefore, conducting and precisely controlling multipath experiments over the real “internet” is a challenging task for some experimenters and impossible for others. In this paper, we invoke SDN technology to make this control possible and exploit large-scale internet testbeds to conduct end-to-end MPTCP experiments. More specifically, we establish a special purpose control and measurement framework on top of two distinct internet testbeds. First, using the OpenFlow support of GÉANT, we build a testbed enabling measurements with real traffic. Second, we design and establish a publicly available large-scale multipath capable measurement framework on top of PlanetLab Europe and show the challenges of such a system. Furthermore, we present measurements results with MPTCP in both testbeds to get insight into its behavior in such not well explored environment.

Optimizing IGP link costs for improving IP-level resilience

Recently, major vendors have introduced new router platforms to the market that support fast IP-level failure protection out of the box. The implementations are based on the IP Fast ReRoute-Loop Free Alternates (LFA) standard. LFA is simple, unobtrusive, and easily deployable. This simplicity, however, comes at a severe price, in that LFA usually cannot protect all possible failure scenarios. In this paper, we give new graph theoretical tools for analyzing LFA failure case coverage and we seek ways for improvement. In particular, we investigate how to optimize IGP link costs to maximize the number of protected failure scenarios, we show that this problem is NP-complete even in a very restricted formulation, and we give exact and approximate algorithms to solve it. Our simulation studies show that a deliberate selection of IGP costs can bring many networks close to complete LFA-based protection.

Optimizing IGP link costs for improving IP-level resilience with Loop-Free Alternates

The IP Fast ReRoute-Loop-Free Alternates (LFA) standard is a simple and easily deployable technique to provide fast failure protection right in the IP layer. To our days, most major IP device vendors have products on the market that support LFA out of the box. Unfortunately, LFA usually cannot protect all possible failure scenarios in a general network topology. Therefore, it is crucial to develop LFA-based network optimization tools in order to assist operators in deciding whether deploying LFA in their network will supply sufficient resiliency. In this paper, we give a new graph theoretical framework for analyzing LFA failure case coverage, and then we investigate how to optimize the Interior Gateway Protocol (IGP) link costs in order to maximize the number of protected failure scenarios. We show that this problem is NP-complete even in a very restricted formulation, and we give an exact algorithm as well as a complete family of heuristics to solve it. Our simulation studies indicate that a deliberate tuning of the approximation strategy can significantly improve the quality of the IGP link costs, and we conclude that LFA cost optimization has the potential for boosting LFA-based resilience in most operational networks significantly.

Dataplane Specialization for High-performance OpenFlow Software Switching

OpenFlow is an amazingly expressive dataplane programming language, but this expressiveness comes at a severe performance price as switches must do excessive packet classification in the fast path. The prevalent OpenFlow software switch architecture is therefore built on flow caching, but this imposes intricate limitations on the workloads that can be supported efficiently and may even open the door to malicious cache overflow attacks. In this paper we argue that instead of enforcing the same universal flow cache semantics to all OpenFlow applications and optimize for the common case, a switch should rather automatically specialize its dataplane piecemeal with respect to the configured workload. We introduce ESwitch, a novel switch architecture that uses on-the-fly template-based code generation to compile any OpenFlow pipeline into efficient machine code, which can then be readily used as fast path. We present a proof-of-concept prototype and we demonstrate on illustrative use cases that ESwitch yields a simpler architecture, superior packet processing speed, improved latency and CPU scalability, and predictable performance. Our prototype can easily scale beyond 100 Gbps on a single Intel blade even with complex OpenFlow pipelines.

Multi-layered Service Orchestration in a Multi-domain Network Environment

In this demo, we show a novel method to multi-layer service orchestration in a multi-domain network. This method is a basic implementation of the three layered concept with multi-layer orchestration designed by the UNIFY project. A global orchestrator is capable of instantiating service elements, i.e., virtual network functions (VNFs), in separate domains. Dedicated local orchestrators indifferent infrastructure domains are responsible for setting up new VNF instances and configuring the underlying network. Our implementation is based on the ESCAPE prototyping framework and an OpenStack (OS) data center with the OpenDaylight (ODL) controller.

A large-scale multipath playground for experimenters and early adopters

Multipath TCP is an experimental transport protocol with remarkable recent past and non-negligible future potential. However the lack of available large-scale testbeds and publicly accessible multiple paths grossly prohibits the adoption of the technology. Here, we demonstrate a large-scale multipath playground deployed on PlanetLab Europe, which can be used either by experimenters and researchers to test and verify their multipath-related ideas (e.g. enhancing congestion control, fairness or even the arrangement of multiple paths) and also by early adopters to enhance their Internet connection even if single-homed.

IP fast reroute with remote Loop-Free Alternates: The unit link cost case

Up to not so long ago, Loop-Free Alternates (LFA) was the only viable option for providing fast protection in pure IP and MPLS/LDP networks. Unfortunately, LFA cannot provide protection for all possible failure cases in general. Recently, the IETF has initiated the Remote Loop-Free Alternates (rLFA) technique, as a simple extension to LFA, to boost the fraction of failure cases covered by fast protection. Before further standardization and deployment, however, it is crucial to determine to what extent rLFA can improve the level of protection in a general IP network, as well as to find optimization methods to tweak a network for 100% rLFA coverage. In this paper, we take the first steps towards this goal by solving these problems in the special, but practically relevant, case when each network link is of unit cost. We also provide preliminary numerical evaluations conducted on real IP network topologies, which suggest that rLFA significantly improves the level of protection, and most networks need only 2 - 3 new links to be added to attain 100% failure case coverage.

Customizable real-time service graph mapping algorithm in carrier grade networks

Today the notion of Service Function Chaining (SFC) returns to the focus of technological development in the area of network management and design. Researchers focus on exploiting the advantages of Network Function Virtualization (NFV) and Software Defined Networking (SDN) to bring SFC to a brand new level of fast and flexible, modern end-to-end service orchestration. The core of SFC architecture is the orchestration algorithm, which has ultimate decision making responsibility over compute and networking resource reservation. There are many sophisticated solutions for this task with long running times, so those cannot be executed real-time for every new request arriving within a few seconds. There is a lack of very fast (meta)heuristic orchestration algorithms to deal with enormous amount of service request. The goal of this paper is to demonstrate novel approaches to designing, evaluating and fine-tuning of real-time parameterizable orchestration algorithms for carrier grade networks.

End-Host Driven Troubleshooting Architecture for Software-Defined Networking

The high variability in traffic demands, the advanced networking services at various layers (e.g., load-balancers), and the steady penetration of SDN technology and virtualization make the crucial network troubleshooting tasks ever more challenging over multi-tenant environments. Service degradation is first realized by the users and, as being the only one having visibility to many relevant information (e.g., connection details) required for accurate and timely problem resolution, the infrastructure layer is often forced upon continuous monitoring resulting in wasteful resource management, not to mention the long time frames. In this paper, we propose an End-host-Driven Troubleshooting architecture (EDT), where users are able to share the application-specific connection details with the infrastructure to accelerate the identification of root causes of performance degradation, and to avoid the need for always-on, resource-intensive, and network-wide monitoring. Utilizing EDT, we provide some essential tools for real end-to-end trace routing (PTR), identifying packet losses, and carry out hop-by- hop latency measurements (HEL). In contrast to existing proposals, PTR traces the practical production traffic without the need of crafted probe packets by means of careful tagging mechanisms and additional ephemeral capturing flow rules. Besides involving negligible data plane deterioration, in certain cases PTR can drastically reduce the time needed to find a traversed path compared to existing solutions. Finally, by means of individual network functions, HEL measures the latency of each link along the found path without involving the controller into the calculation, hence resulting in significant reduction of control plane overhead.