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

The microbiome of the uropygial secretion in hoopoes is shaped along the nesting phase

Microbial symbiont acquisition by hosts may determine the effectiveness of the mutualistic relationships. A mix of vertical and horizontal transmission may be advantageous for hosts by allowing plastic changes of microbial communities depending on environmental conditions. Plasticity is well known for gut microbiota but is poorly understood for other symbionts of wild animals. We here explore the importance of environmental conditions experienced by nestling hoopoes (Upupa epops) during the late nesting phase determining microbiota in their uropygial gland. In cross-fostering experiments of 8 days old nestlings, “sibling-sibling” and “mother-offspring” comparisons were used to explore whether the bacterial community naturally established in the uropygial gland of nestlings could change depending on experimental environmental conditions (i.e., new nest environment). We found that the final microbiome of nestlings was mainly explained by nest of origin. Moreover, cross-fostered nestlings were more similar to their siblings and mothers than to their stepsiblings and stepmothers. We also detected a significant effect of nest of rearing, suggesting that nestling hoopoes acquire most bacterial symbionts during the first days of life but that the microbiome is dynamic and can be modified along the nestling period depending on environmental conditions. Estimated effects of nest of rearing, but also most of those of nest of origin are associated to environmental characteristics of nests, which are extended phenotypes of parents. Thus, natural selection may favor the acquisition of appropriated microbial symbionts for particular environmental conditions found in nests.Support by funding was provided by Spanish Ministerio de Economía y Competitividad, European funds (FEDER) (CGL2013-48193-C3-1-P, CGL2013-48193-C3-2-P), and Junta de Andalucía (P09-RNM-4557). AM-G had a predoctoral grant from the Junta de Andalucía (P09-RNM-4557).Peer reviewe

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

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

Scaling and Interoperability of All-Path with Bridged and SDN Domains using VXLANs

The 44th IEEE Conference on Local Computer Networks (LCN), October 14-17, 2019, Osnabrück, Germany.All-Path protocols, namely ARP-Path and TCPPath, provide shortest path bridging by using path discovery and backwards learning in meshed topologies. However, their domain size may be limited to prevent excessive Layer 2 (L2) broadcast traffic overload in hosts. This paper proposes the use of Virtual Extensible Local Area Network (VXLAN) to solve this issue. Moreover, this paper also verifies the extensibility of All-Path domains and its interoperability with other different L2 protocols via VXLAN, which enables flexible network hybridization. Although encapsulation via VXLAN is heavier than other standard protocols designed for L2 scalability, the overall advantages and suitability for virtualized networks are excellent. Results show full compatibility and interoperability combined with good throughput and delay performance.Comunidad de MadridUniversidad de Alcal

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

All-Path Bridging: Path Exploration Protocols for Data Center and Campus Networks

Today, link-state routing protocols that compute multiple shortest paths predominate in data center and campus networks, where routing is performed either in layer three or in layer two using link-state routing protocols. But current proposals based on link-state routing do not adapt well to real time traffic variations and become very complex when attempting to balance the traffic load. We propose All-Path bridging, an evolution of the classical transparent bridging that forwards frames over shortest paths using the complete network topology, which overcomes the limitations of the spanning tree protocol. All-Path is a new frame routing paradigm based on the simultaneous exploration of all paths of the real network by a broadcast probe frame, instead of computing routes on the network graph. This paper presents All- Path switches and their differences with standard switches and describes ARP-Path protocol in detail, its path recovery mechanisms and compatibility with IEEE 802.1 standard bridges. ARP-Path is the first protocol variant of the All-Path protocol family. ARP-Path reuses the standard ARP Request and Reply packets to explore reactively the network and find the fastest path between two hosts. We compare its performance in terms of latency and load distribution with link-state shortest-path routing bridges, showing that ARP-Path distributes the load more evenly and provides lower latencies. Implementations on different platforms prove the robustness of the protocol. The conclusion is that All-Path bridging offer a simple, resilient and scalable alternative to path computation protocols

All-Path Bridging: Path Exploration Protocols for Data Center and Campus Networks

Today, link-state routing protocols that compute multiple shortest paths predominate in data center and campus networks, where routing is performed either in layer three or in layer two using link-state routing protocols. But current proposals based on link-state routing do not adapt well to real time traffic variations and become very complex when attempting to balance the traffic load. We propose All-Path bridging, an evolution of the classical transparent bridging that forwards frames over shortest paths using the complete network topology, which overcomes the limitations of the spanning tree protocol. All-Path is a new frame routing paradigm based on the simultaneous exploration of all paths of the real network by a broadcast probe frame, instead of computing routes on the network graph. This paper presents All- Path switches and their differences with standard switches and describes ARP-Path protocol in detail, its path recovery mechanisms and compatibility with IEEE 802.1 standard bridges. ARP-Path is the first protocol variant of the All-Path protocol family. ARP-Path reuses the standard ARP Request and Reply packets to explore reactively the network and find the fastest path between two hosts. We compare its performance in terms of latency and load distribution with link-state shortest-path routing bridges, showing that ARP-Path distributes the load more evenly and provides lower latencies. Implementations on different platforms prove the robustness of the protocol. The conclusion is that All-Path bridging offer a simple, resilient and scalable alternative to path computation protocols

Implementing ARP-Path Low Latency Bridges in NetFPGA

The demo is focused on the implementation of ARP-Path (a.k.a. FastPath) bridges, a recently proposed concept for low latency bridges. ARP-Path Bridges rely on the race between broadcast ARP Request packets, to discover the minimum latency path to the destination host. Several implementations (in Omnet++, Linux, OpenFlow, NetFPGA) have shown that ARP-Path exhibits loop-freedom, 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. This demo compares our hardware implementation on NetFPGA to bridges running STP, showing that ARP-Path finds lower latency paths than STP

A Simple, Zero-configuration, Low Latency, Bridging Protocol

This paper describes a demo for a new type of bridges, ARP-Path bridges. These ARP-based Ethernet Switches rely on the race between ARP Request packets flooded over all links, to discover the minimum latency path to the destination host. The protocol uses all links, is loop free, uses the standard Ethernet frame format, is fully transparent to hosts and neither needs a spanning tree protocol to prevent loops nor a links state protocol to obtain minimum latency paths. Implementations in Linux and Openflow on NetFPGA show inherent robustness and fast reconfiguration. Simulation results show throughput and delay performance superior to the Spanning Tree Protocol and similar to shortest path routing, with lower complexity