Contribución al diseño de conmutadores transparentes avanzados basados en tecnología Ethernet

Aunque los conmutadores Ethernet son ya el elemento clave en las redes actuales campus, empresariales y de centros de proceso de datos por sus altas prestaciones, coste moderado y mínima configuración, los protocolos de capa dos actuales no tienen la escalabilidad y robustez suficientes para utilizarse en redes campus de tamaño medio y precisan el uso de encaminadores (routers) que compartimenten la red. Estas redes de tamaño y capacidad crecientes requieren nuevos dispositivos que superen las limitaciones de escalabilidad de los puentes y la complejidad de configuración de los encaminadores. Desde 2004 se vienen estandarizando dos propuestas divergentes aunque ambas basadas en introducir encaminamiento por estado de enlaces en capa dos: TRILL y Shortest Path Bridges. Asimismo han aparecido diversas propuestas propietarias de fabricantes e investigadores. Pero aún no existe consenso sobre la adecuación de dichas soluciones a los problemas planteados por la escalabilidad de Ethernet en los escenarios mencionados debido a las dificultades del problema planteado de hacer Ethernet escalable manteniendo la compatibilidad y la simplicidad en la arquitectura. Este trabajo aporta varias contribuciones en el campo de los conmutadores Ethernet Avanzados para redes campus y centros de datos que se enmarcan en una línea propia de investigación de conmutadores Ethernet auto-configurables, desarrollada en la Universidad de Alcalá en los últimos seis años, que, partiendo de la investigación en protocolos de prohibición de giros y de encaminamiento jerárquico ha desembocado en la reciente arquitectura de conmutadores All-Path/ARP-Path que recupera la simplicidad de los puentes a través de su evolución como tales en vez de la hibridación con protocolos de encaminamiento. Entre las contribuciones de la Tesis se incluyen protocolos de Ethernet de encaminamiento basados en árbol y protocolos jerárquicos Up/Down y múltiples contribuciones a la definición, especificación, análisis y validación de la nueva familia de protocolos All-Path

eHDDP: Enhanced Hybrid Domain Discovery Protocol for network topologies with both wired/wireless and SDN/non-SDN devices

Handling efficiently both wired and/or wireless devices in SDN networks is still an open issue. eHDDP comes as an enhanced version of the Hybrid Domain Discovery Protocol (HDDP) that allows the SDN control plane to discover and manage hybrid topologies composed by both SDN and non-SDN devices with wired and/or wireless interfaces, thus opening a path for the integration of IoT and SDN networks. Moreover, the proposal is also able to detect both unidirectional and bidirectional links between wireless devices. eHDDP has been thoroughly evaluated in different scenarios and exhibits good scalability properties since the number of required messages is proportional to the number of existing links in the network topology. Moreover, the obtained discovery and processing times give the opportunity to support scenarios with low mobility devices since the discovery times are in the range of hundreds of milliseconds.Comunidad de MadridJunta de Comunidades de Castilla-La Manch

A Performance Comparison of Virtual Backbone Formation Algorithms for Wireless Mesh Networks

Currently wireless networks are dominant by star topology paradigm. Its natural the evolution is towards wireless mesh multi-hop networks. This article compares the performance of several algorithms for virtual backbone formation in ad hoc mesh networks both theoretically and through simulations. Firstly, an overview of the algorithms is given. Next, the results of the algorithm simulations made with the program Dominating Set Simulation Suite (DSSS) are described and interpreted. We have been extended the simulator to simulate the Mobile Backbone Network Topology Synthesis Algorithm. The results show that this algorithm has the best combination of performance characteristics among the compared algorithms

A hybrid SDN switch based on standard P4 code

This paper presents an enhanced hybrid Software-Defined Networking (SDN) layer-2 switch whose behavior is specified by the Programming Protocol-independent Packet Processors (P4) language. Its SDN capabilities are enabled by using P4Runtime as control plane protocol to specify the forwarding rules used by its programmable data plane. Additionally, the device is also able to exploit P4 registers for an autonomous self-definition of its forwarding capabilities, with the goal of avoiding an overload of the SDN control plane. Its performance is better than other P4 proposals based on non-standard externs and similar to other platform-dependent implementations.Comunidad de MadridJunta de Comunidades de Castilla-La ManchaUniversidad de Alcal

The disjoint multipath challenge: multiple disjoint paths guaranteeing scalability

The multipath challenge is a research line in continuous development because of its multiple benefits, however, these benefits are overshadowed by scalability, which goes down considerably when the paths are multiple and disjoint. The disjointness aggregates an extra value to the multiple paths, but it also implies more complex mathematical operations that increase the computational cost. In fact, diverse proposals exist that try to increase scalability by limiting the number of paths obtained to the minimum possible (two-disjoint paths), which is enough for backup applications but not for other purposes. This paper presents an algorithm that solves these drawbacks by discovering multiple disjoint paths among multiple nodes in an efficient way, while keeping bounded the computational cost and ensuring scalability. The proposed algorithm has been validated thoroughly by performing a theoretical analysis, bolstered afterwards by an exhaustive experimental evaluation. The collected results are promising, our algorithm reduces the time spent to obtain the disjoint paths regarding its competitors between one and three orders of magnitude, at the cost of a slight decrease in the number of paths discovered.Comunidad de MadridJunta de Comunidades de Castilla-La Manch

One-Shot Multiple Disjoint Path Discovery Protocol (1S-MDP)

Multipath routing over disjoint paths is a classic solution to allow better resource allocation, resilience, and security. Current proposals rely on centralised computation or iterative distributed algorithms and exhibit large convergence times. We propose 1S-MDP, a distributed mechanism based on a single network exploration with concurrent path selection to discover multiple available paths among the target node and the remaining nodes in the network. The paper evaluates 1S-MDP in two different scenarios against previous solutions. We show how it reduces the convergence time by several orders of magnitude with a small decrease in the number of disjoint paths discovered.Comunidad de Madri

Improving multipath routing of TCP flows by network exploration

Ethernet switched networks are widely used in enterprise and data center networks. However, they have some drawbacks, mainly that, to prevent loops, they cannot take advantage of multipath topologies to balance traffic. Several multipath routing proposals use link-state protocols and Equal Cost Multi-Path routing (ECMP) to distribute the load over multiple paths. But, these proposals are complex and prone to flow collisions that may degrade performance. This paper studies TCP-Path, a protocol that employs a different approach. It uses a distributed network exploration mechanism based on broadcasting the TCPSYN packet to identify and select the fastest available path to the destination host, on the fly. Our evaluation shows that it improves on ECMP by up to 70% in terms of throughput for elephant flows and by up to 60% in terms of flow completion time for mouse flows. Indeed, network exploration offers a better, yet simple alternative to ECMP-based solutions for multipath topologies. In addition, we also study TCP-Path for elephant flows (TFE), which restricts TCP-Path application to elephant flows to reduce the exploration broadcast overhead and the size of forwarding tables, thus improving its scalability. Although elephant flows represent a small fraction (about 5%) of total flows, they have a major impact on overall performance, as we show in our evaluation. TFE reduces both the overhead incurred during path setup and the size of the forwarding tables by a factor of almost 20. Moreover, it achieves results close to those obtained by TCPPath for elephant flows, especially when working with high loads, and yields significant improvements for all types of flow at medium and high load levels.Comunidad de MadridUniversidad de Alcal

GA3: scalable, distributed address assignment for dynamic data center networks

Deployment and maintenance of current data center networks is costly and prone to errors. In order to avoid manual configuration, many of them require centralized administrators which constitute a clear bottleneck, while distributed approaches do not guarantee sufficient flexibility or robustness. This paper describes and evaluates GA3 (Generalized Automatic Address Assignment), a discovery protocol that assigns multiple unique labels to all the switches in a hierarchical network, without any modification of hosts or the standard Ethernet frames. Labeling is distributed and uses probes. These labels can be leveraged for shortest path routing without tables, as in the case of the Torii protocol, but GA3 also allows other label-based routing protocols (such as PortLand or ALIAS). Additionally, GA3 can detect miswirings in the network. Furthermore, control traffic is only necessary upon network deployment rather than periodically. Simulation results showed a reduced convergence time of less than 2 s and 100 kB/s of bandwidth (to send the GA3 frames) in the worst case for popular data center topologies, which outperforms other similar protocols.Comunidad de Madri

TEDP: an enhanced topology discovery service for Software-Defined Networking

Currently, software-defined networking (SDN) platforms leverage the link-layer discovery protocol (LLDP) to discover the underlying topology. However, the LLDP is suboptimal in terms of message load. In this letter, we present the tree exploration discovery protocol (TEDP), proving that shortest paths can be built at the same time that the topology information is gathered, without extra messages compared with LLDP. We also analyze two alternative implementations for the TEDP and give insights into some features that SDN platforms should ideally provide for an efficient topology discovery service.Comunidad de Madri

Implementation of ARP-Path Low Latency Bridges in Linux and OpenFlow/NetFPGA

This paper describes the implementation of ARP- Path (a.k.a. FastPath) bridges, a recently proposed concept for low latency bridges, in Linux/Soekris and OpenFlow/NetFPGA platforms. These ARP-based Ethernet Switches rely on the race between the replicas of a standard ARP Request packet flooded over all links, to discover the minimum latency path to the destination host, complemented in the opposite direction by the ARP Reply packet directed to the source host. Implementations show that the protocol is loop free, does not block links, is fully transparent to hosts and neither needs a spanning tree protocol to prevent loops nor a link state protocol to obtain low latency paths. Implementations in Linux and OpenFlow on NetFPGA show inherent robustness and fast reconfiguration. Previous simulations showed a superior performance (throughput and delay) than the Spanning Tree Protocol and similar to shortest path routing, with lower complexity.Ministerio de Ciencia e InnovaciónComunidad de MadridJunta de Comunidades de Castilla-La Manch