Search

Every data packet routed over the internet finds its route based on decisions within the BGP protocol. In 2022 there are already over 100 000 AS numbers registered with an authority in order to participate in BGP routing. With such an important routing protocol as BGP, it is clearly essential to think about what happens if one of the routes should fail for physical or logical reasons. BGP requires at least two different connections to different BGP partners for correct installation. This ensures that several routes can always lead to one destination. However, the question now arises as to how long it takes in BGP until the failure of one path is detected and another path is accepted. In order to answer this question, a physical as well as a logical failure is examined, and the convergence time is measured. Also considered is the most commonly used protocol to reduce convergence times in BGP, the Bidirectional Forwarding Detection (BFD). David Hasenhüttl Bachelorarbeit FH JOANNEUM 2022

This document defines a YANG data model that can be used to configure and manage Bidirectional Forwarding Detection (BFD). The YANG modules in this document conform to the Network Management Datastore Architecture (NMDA).

The network protocol BFD (Bidirectional Forwarding Detection) that detects issues between duplet forwarding engines. With minimum overhead, it detects flaws in physical media that doesn't allow for any kind of finding defects, including Ethernet, MPLS label switched channels, tunnels, and virtual circuits. One of the features is to verify the functionalities of static BFD. The work modes in BTS are Asynchronous mode, Demand mode, Echo mode. Currently only Asynchronous mode is supported in WBTS. BFD can be configured in two ways: Single hop and multi hop. Configured and commissioned the BTS & TRS setup in SEM tool and configured BFD in SEM (Site Element Manager) tool. BTS has come ON AIR and CS (Circuit Switch) PS (Packet Switch) calls are processing. Here we are checking the functionality of BFD whether it detects faults properly or not and removing routing connection from router side and check BFD alarm show up or not in SEM. Several calls are successfully placed after functionality check. Complete BFD process setting up and functionality check is automated. Where its check switch and router configuration as precondition and then perform BTS commissioning, checks BTS RNC BFD alarms and also placed call automatically. For switch, router configuration check and Wireshark log collection several key words are designed in Robot framework format so that script can be easily understandable by anyone. Configuring and verifying BIDIRECTIONAL FORWARDING DETECTION functionality in WCDMA Base Transceiver station (WBTS) is done manually and automated the complete process.

Network failures can significantly degrade the network performance in several ways, ranging from experiencing unacceptable delays (e.g., in video conference applications) to leading to significant drops in sales for companies (e.g., airlines tickets purchases). In this paper, we focus on network failures caused by links that are prone to fail due to their advanced stage of lifetime. In particular, the formalization of the Hardware Deterioration Failure Mode (HDFM) for network line cards is provided to evaluate the penalty for network operators of handling HDFM failing links using classical methods based on Bidirectional Forwarding Detection and Fast Re-Route mechanisms. An algorithm, named Hardware Deterioration Detection (HDD), is proposed to detect if links are experiencing failures as well as to provide an estimation of their remaining lifetime. The performance evaluation over data generated by our provided network failure simulator shows that HDD is able to correctly classify links as failing or not failing, regardless of the type of failure considered. Moreover, overall descriptions for failure models in which HDD is able to produce high quality estimations of the remaining lifetime have been identified, with a trade-off between the hardware deterioration time dependence and the relationship between lifetime and packet loss probability.

This document describes the use of the Bidirectional Forwarding Detection (BFD) protocol in point-to-point Virtual eXtensible Local Area Network (VXLAN) tunnels used to form an overlay network.

Software-defined networking (SDN) promises unprecedentedly flexible network management but it is susceptible to forwarding faults. Such faults originate from data-plane rules with missing faults and priority faults. Yet existing fault detection ignores priority faults, because they are not discovered on commercial switches until recently. In this paper, we present RuleScope, a more comprehensive solution for inspecting SDN forwarding. RuleScope offers a series of accurate and efficient algorithms for detecting and troubleshooting rule faults. They inspect forwarding behavior using customized probe packets to exercise data-plane rules. The detection algorithm exposes not only missing faults but also priority faults and the troubleshooting algorithm uncover actual forwarding states of data-plane flow tables. Both of them help track real-time forwarding status and benefit reliable network monitoring. Furthermore, toward fast inspection of dynamic networks, we propose incremental algorithms for rapidly evolving network policies to amortize detection and troubleshooting overhead without sacrificing accuracy. Experiments with our prototype on the Ryu SDN controller and Pica8 P-3297 switch show that the RuleScope achieves accurate fault detection on 320-entry flow tables with a cost of 1500+ probe packets within 16 s.

One of the most challenging issues in Mobile Social Networks (MSNs) is to design a messages forwarding method that achieves high delivery and low communication overhead. Single-copy forwarding methods boasting minimum communication overhead are well-known in MSNs. However, attaining a reasonable delivery ratio by using a single-copy method is an open problem. A common way to resolve the problem is social-aware forwarding, but this faces two main weaknesses: one is that they either are unaware of community detection, or use supervised learning strategies, other is that they generally use the relay-destination contact probability for predicting future contacts without considering the contact time. In this paper, we propose community-aware forwarding (CAF) as a new single-copy forwarding method using Hidden Semi-Markov Model (HSMM) to find communities by utilizing the similarity of node contact patterns in different sojourn cycles. In this study, we train HSMM as an unsupervised algorithm to compute the node community transition and then propose a novel forwarding method that utilizes message expiration in order to make relay selection. Evaluation results confirm our superior CAF performance over the popular solutions investigated in terms of message delivery and latency.

Micro aerial vehicles (MAVs) provide data such as images and videos from an aerial perspective, with data typically transferred to the ground. To establish connectivity in larger areas, a fleet of MAVs may set up an ad-hoc wireless network. Packet forwarding in aerial networks is challenged by unstable link quality and intermittent connectivity caused by MAV movement. We show that signal obstruction by the MAV frame can be alleviated by adapting the MAV platform, even for low-priced MAVs, and the aerial link can be properly characterized by its geographical distance. Based on this link characterization and making use of GPS and inertial sensors on-board of MAVs, we design and implement a motion-driven packet forwarding algorithm. The algorithm unites location-aware end-to-end routing and delay-tolerant forwarding, extended by two predictive heuristics. Given the current location, speed, and orientation of the MAVs, future locations are estimated and used to refine packet forwarding decisions. We study the forwarding algorithm in a field measurement campaign with quadcopters connected over Wi-Fi IEEE 802.11n, complemented by simulation. Our analysis confirms that the proposed algorithm masters intermittent connectivity well, but also discloses inefficiencies of location-aware forwarding. By anticipating motion, such inefficiencies can be counteracted and the forwarding performance can be improved. pub

In wireless sensor networks, sensed information is expected to be reliably and timely delivered to a sink in an ad-hoc way. However, it is challenging to achieve this goal because of the highly dynamic topology induced from asynchronous duty cycles and temporally and spatially varying link quality among nodes. Currently some opportunistic forwarding protocols have been proposed to address the challenge. However, they involve complicated mechanisms to determine the best forwarder at each hop, which incurs heavy overheads for the resource-constrained nodes. In this paper, we propose a light-weight opportunistic forwarding (LWOF) scheme. Different from other recently proposed opportunistic forwarding schemes, LWOF employs neither historical network information nor a contention process to select a forwarder prior to data transmissions. It confines forwarding candidates to an optimized area, and takes advantage of the preamble in low-power-listening (LPL) MAC protocols and dual-channel communication to forward a packet to a unique downstream node towards the sink with a high probability, without making a forwarding decision prior to data transmission. Under LWOF, we optimize LPL MAC protocol to have a shortened preamble (LWMAC), based on a theoretical analysis on the relationship among preamble length, delivery probability at each hop, node density and sleep duration. Simulation results show that LWOF, along with LWMAC, can achieve relatively good performance in terms of delivery reliability and latency, as a receiver-based opportunistic forwarding protocol, while reducing energy consumption per packet by at least twice.

In the absence of end-to-end paths and without the knowledge of the whole network, packet forwarding, including forwarding decision (i.e., forwarding or dropping the packet) and relaying selection, is crucial to be made by the individual of the node based on the packet-forwarding protocol in autonomous mobile social networks (MSNs). In this paper, we investigate the adaptive packet forwarding in MSNs afflicted with potential selfish nodes. When considering the various selfish behaviors of network nodes in multi-hop MSNs, an incentive compatible multiple-copy packet forwarding (ICMPF) protocol is proposed to maintain a satisfied packet delivery probability while reducing the delivery overhead. Considering the fact that the node’s forwarding decision in the ICMPF protocol is affected by its available resources (i.e., bandwidth and location privacy) and network environment (i.e., other nodes’ actions and social ties), an evolutionary game framework is exploited for modeling the complicated interactions among nodes to guide their forwarding behaviors. Meanwhile, we portray the forwarding behavior dynamics and develop the evolutionary stable strategy (ESS) for this game-theoretic framework. Then, we prove that the strategy dynamics converge to the ESS and further develop a distributed learning algorithm for nodes to approach to the ESS. Simulation results show that our system converges to the ESS and also is robust to the learning error induced by the communication noise.

When a routing protocol detects a link or node failure, a network convergence process starts in the network. This process may take from a few hundred ms to tens of seconds. During this process, the data affected by specific failure is permanently lost. For these reasons, Fast ReRoute (FRR) has been developed. FRR is a technology, that minimizes network repair time after a link or node failure, mainly in the ISP networks. The FRR mechanisms calculate alternative backup path before the failure in the network may occur. The key factor of network recovery time after link or node failure is failure detection. One of common fast failure detection technique used in the FRR area is Bidirectional Forwarding Detection (BFD) mechanism. In this paper we present a new implementation of fast failure detection mechanism BFD in discrete event simulator OMNeT++. We describe implementation of individual modules in simulator, testing topology and testing scenarios for proper validation.

The infrastructure necessary to support convergent network services is increasingly more complex than the usual communication networks. A network device must be able to quickly detect any communication failure between adjacent devices for the upper-layer protocol to be able rectify this failure and prevent any interruptions in services. Convergent networks use Hello routing protocol from the upper layer to detect failures. The detection period, dependent on issues intrinsic to the protocol and the arrangement of the network configuration, can lead to high downtimes in case of unavailability of the main circuit and of switch to the backup circuit. In this context, considering a real corporate network in a production environment, there is the need to carry out experiments aimed at obtaining a scenario that can offer the lowest downtime and, consequently, a greater network availability. This work is aimed at carrying out an inferential performance assessment through a paired before-and-after comparison in order to obtain the best convergence condition for a corporate network and consequently offer greater availability. For that aim, we have proposed a Continuous-Time Markov Chain (CTMC) that represents convergent network architectures considering the Border Gateway Protocol (BGP) and Bidirectional Forwarding Detection (BFD) protocol for supporting availability evaluation. In addition, we presented a closed-form equation derived from the proposed CTMC for calculating the availability of critical warm standby components by system considering its size. The work also presents a sensitivity analysis of network availability as a result of fail over time. Our approach has proven to be feasible, and it highlights the most appropriate scenarios, supporting network architects at design time.

This document describes extensions to the Bidirectional Forwarding Detection (BFD) protocol for its use in multipoint and multicast networks. This document updates RFC 5880.

As the scale of MPLS RSVP-TE networks has grown, so the number of Label Switched Paths (LSPs) supported by individual network elements has increased. Various implementation recommendations have been proposed to manage the resulting increase in control plane state. However, those changes have had no effect on the number of labels that a transit Label Switching Router (LSR) has to support in the forwarding plane. That number is governed by the number of LSPs transiting or terminated at the LSR and is directly related to the total LSP state in the control plane. This document defines a mechanism to prevent the maximum size of the label space limit on an LSR from being a constraint to control plane scaling on that node. It introduces the notion of pre-installed 'per Traffic Engineering (TE) link labels' that can be shared by MPLS RSVP-TE LSPs that traverse these TE links. This approach significantly reduces the forwarding plane state required to support a large number of LSPs. This couples the feature benefits of the RSVP-TE control plane with the simplicity of the Segment Routing MPLS forwarding plane.

Point to multipoint (P2MP) BFD is designed to verify multipoint connectivity. This document specifies the support of P2MP BFD in TRILL. Similar to TRILL point-to-point BFD, BFD Control packets in TRILL P2MP BFD are transmitted using RBridge Channel messages. This document updates RFC 7175 and RFC 7177.

This document describes active tail extensions to the Bidirectional Forwarding Detection (BFD) protocol for multipoint networks.

Multiprotocol Label Switching (MPLS) is a relatively new WAN technology that is attracting the networking professionals around the globe. Many ISPs have already deployed it in their network. Yet, some other ISPs are in the pipeline to deploy it. Nevertheless, it has caught the attention of professionals soon after it was developed. Instead of the IP address or MAC address, MPLS works on small labels. These labels are inserted between Data Link layer and Network layer of the OSI model. Forwarding decisions are based on these labels; instead of looking at complex routing tables. The MPLS network is configured, and tested under different conditions. A comparison is drawn between the IP and MPLS network. The obtained results show that MPLS has a lower end to end delay and less CPU utilization. Furthermore, MPLS has lesser processing delay as compared to the IP network. The performance difference is basically due to the intelligent forwarding mechanism of MPLS technology. It is also important to further investigate this topic in terms of security considerations. The labels values are not encrypted during transmission, and there is no authorization mechanism defined. It will be highly beneficial to have more sophisticated suite of security tools to encounter threats and vulnerabilities.

Named Data Networking (NDN) is a new Internet architecture which has been proposed to eliminate TCP/IP Internet architecture restrictions. This architecture is abstracting away the notion of host and working based on naming datagrams. However, one of the major challenges of NDN is supporting QoS-aware forwarding strategy so as to forward Interest packets intelligently over multiple paths based on the current network condition. In this paper, Neural Network (NN) Based Traffic-aware Forwarding strategy (NNTF) is introduced in order to determine an optimal path for Interest forwarding. NN is embedded in NDN routers to select next hop dynamically based on the path overload probability achieved from the NN. This solution is characterized by load balancing and QoS-awareness via monitoring the available path and forwarding data on the traffic-aware shortest path. The performance of NNTF is evaluated using ndnSIM which shows the efficiency of this scheme in terms of network QoS improvementof17.5% and 72% reduction in network delay and packet drop respectively.

In this paper, an environment-driven cross-layer optimization scheme is proposed to maximize packet forwarding efficiency. The proposed algorithm is aimed to improve the performance of location-based routing protocol in respect of greedy forwarding and avoid void regions for ubiquitous wireless networks. In greedy forwarding mode, we use a new routing metric IAPS which can estimate the forwarding distance, link quality and the difficulty of channel access during the process of the next hop node selection. When the packet forwarding comes into a local minimum, the proposed scheme uses an opportunistic forwarding method based on competitive advantage to bypass the void regions. NS2 simulation results indicate that the proposed algorithm can improve network resource utilization and the average throughput, and reduce congestion loss rate of wireless multi-hop network comparison with existing GPSR algorithm.

Greedy Perimeter Stateless Routing (GPSR) gives the good forwarding nodes for Mobile Ad Hoc Networks (MANET) but does not provide the right directional forwarding nodes in Vehicular Ad Hoc Network (VANET). This is the fact that MANET uses the nodes without limitations in moving but VANET uses fixed infrastructure in mobility such as roads with lanes. The key of original greedy forwarding is choosing the forwarding node with the shortest distance between the source and the destination. It does not consider the direction of the forwarding nodes, which possibly cause the selected forwarding node going opposite direction from the destination. This paper thus tries to improve the greedy forwarding method of Greedy Perimeter Stateless Routing (GPSR) by taking into considerations in both the distance and the direction. Moreover it shows the mystery of angle that gives the right direction. The optimized GPSR (OGPSR) using improved greedy forwarding provides the better throughput, average end-to-end delay and routing overheads than the original GPSR.

Long-term evolution (LTE)/LTE-advanced (LTE-A) networks have recently introduced a data packet forwarding scheme between evolved node Bs (eNBs) to reduce the signaling overhead and the delay incurred in the data path switching scheme, which is a baseline handover scheme in LTE/LTE-A networks. Even with the data packet forwarding scheme, if the length of the forwarding chain is set inappropriately, the data packet forwarding scheme suffers from the degraded throughput. To attain the optimal handover performance in terms of throughput and delay and reduce the signaling overhead, we propose an optimized and distributed data packet forwarding scheme where the optimal length of the forwarding chain is obtained by a Markov decision process (MDP). In addition, a low-complexity value iteration algorithm is devised to solve the optimality equation of MDP in a more practical manner. Real trace-driven evaluation results demonstrate that the proposed scheme determines the optimal length of the forwarding chain adaptively to the applications' quality-of-service (QoS) requirements and reduces the signaling overhead and delay while achieving higher throughput in diverse environments.

Wireless sensor networks (WSNs) are vulnerable to selective forwarding attacks that can maliciously drop a subset of forwarding packets to degrade network performance and jeopardize the information integrity. Meanwhile, due to the unstable wireless channel in WSNs, the packet loss rate during the communication of sensor nodes may be high and vary from time to time. It poses a great challenge to distinguish the malicious drop and normal packet loss. In this paper, we propose a channel-aware reputation system with adaptive detection threshold (CRS-A) to detect selective forwarding attacks in WSNs. The CRS-A evaluates the data forwarding behaviors of sensor nodes, according to the deviation of the monitored packet loss and the estimated normal loss. To optimize the detection accuracy of CRS-A, we theoretically derive the optimal threshold for forwarding evaluation, which is adaptive to the time-varied channel condition and the estimated attack probabilities of compromised nodes. Furthermore, an attack-tolerant data forwarding scheme is developed to collaborate with CRS-A for stimulating the forwarding cooperation of compromised nodes and improving the data delivery ratio of the network. Extensive simulation results demonstrate that CRS-A can accurately detect selective forwarding attacks and identify the compromised sensor nodes, while the attack-tolerant data forwarding scheme can significantly improve the data delivery ratio of the network.

Heterogeneity arises in a wide range of scenarios in mobile opportunistic networks and is one of the key factors that govern the performance of forwarding algorithms. While the heterogeneity has been empirically investigated and exploited in the design of new forwarding algorithms, it has been typically ignored or marginalized when it comes to rigorous performance analysis of such algorithms. In this paper, we develop an analytical framework to quantify the performance gain achievable by exploiting the heterogeneity in mobile nodes’ contact dynamics. In particular, we derive a delay upper bound of a heterogeneity-aware static forwarding policy per each given number of message copies and obtain its closed-form expression, which enables our quantitative study on the benefit of leveraging underlying heterogeneity structure in the design of forwarding algorithms. In addition, we develop a dynamic forwarding policy that performs as an extension of the static forwarding policy while proven to improve the delay performance. We then demonstrate that only a small fraction of total (unlimited) message copies, via both static and dynamic forwarding policies, are enough under various heterogeneous network settings to achieve the same delay as that obtained using the unlimited message copies when the networks become homogeneous. We also show that, given the same number of message copies, our dynamic forwarding policy significantly outperforms the ‘homogeneous-optimal’ forwarding policy (up to about 50 percent improvement in the delay performance), especially when the number of message copies allowed in the networks is small.

The forwarding scheme in Software-Defined Networking (SDN) is usually coupled with flow table management. To reduce the redundancy in the flow tables of OpenFlow switches, some recent studies propose forwarding flows using stacked MPLS labels, in which each label in the stack indicates the forwarding decision at one hop of the forwarding route. However, using multiple MPLS labels in each packet introduces significant transmission overhead, especially in networks with large diameters. In this paper, we propose JumpFlow, a forwarding scheme that achieves low and balanced flow table usage in an SDN by properly and reactively placing flow entries on switches. To reduce the transmission overhead, JumpFlow uses the available VLAN identifier (VID) in the packet header to carry routing information. Constrained by the limited space of the VID, a flow’s complete routing information must be divided into several sections and loaded separately at different switches on the flow’s forwarding route. To achieve low and balanced flow table usage, we formulate and solve the reactive flow entry placement problem. We evaluate JumpFlow against the per-hop configuration-based forwarding of OpenFlow for both unicast and multicast scenarios in a real network topology with different traffic patterns. For the unicast scenario with different new flow arrival rates, JumpFlow postpones the time when the first flow rejection occurs, reduces the flow rejection percentage by 37.06%, and reduces the control messages for route configuration by 53.52% on average. For the multicast scenario with a high new multicast group arrival rate, JumpFlow increases the ratio of accepted multicast groups by 83.90%, and reduces the ratio of average control messages for a multicast group configuration by 32.68%.

In delay tolerant networks, most of the existing message forwarding algorithms prefer to deliver messages to the nodes with a higher popularity or centrality in the hope of maximizing the delivery ratio or minimizing the end-to-end delay. This forwarding scheme is prone to cause unfair load distribution and further lead to network congestion, overlooked in the previous work. In this paper, we discuss the network congestion from a community perspective and take it into account the design of message forwarding algorithms. We first put forward a novel distributed community detection approach, which could track the evolution of communities. Based on the identified communities, we develop a congestion avoidance mechanism to divert the load away from the congested areas to the alternative custodians and further present a congestion-aware message forwarding algorithm where messages can avoid being transmitted to the congested nodes. We finally evaluate the effectiveness of distributed community detection and congestion-aware message forwarding through the extensive real-trace driven simulations. Copyright © 2015 John Wiley & Sons, Ltd.

Opportunistic mobile networks consist of mobile devices which are intermittently connected via short-range radios. Forwarding in such networks relies on selecting relays to carry and deliver data to destinations upon opportunistic contacts. Due to the intermittent network connectivity, relays in current forwarding schemes are selected separately in a distributed manner. The contact capabilities of relays hence may overlap when they contact the same nodes and cause forwarding redundancy . This redundancy reduces the efficiency of resource utilization in the network, and may impair the forwarding performance if being unconsciously ignored. In this paper, based on investigation results on the characteristics of forwarding redundancy in realistic mobile networks, we propose methods to eliminate unnecessary forwarding redundancy and ensure efficient utilization of network resources. We first develop techniques to eliminate forwarding redundancy with global network information, and then improve these techniques to be operable in a fully distributed manner with limited network information. We furthermore propose adaptive forwarding strategy to intentionally control the amount of forwarding redundancy and satisfy the required forwarding performance with minimum cost. Extensive trace-driven evaluations show that our schemes effectively enhance forwarding performance with much lower cost.

We study a forwarding strategy in opportunistic networks which are one of the most challenging networks among mobile ad-hoc networks. In opportunistic networks, a node does not have knowledge about the entire network topology, which is essential in the mobile ad-hoc network's forwarding strategy. Thus, node behavior is exploited to calculate future contact opportunities for forwarding a message. Utilizing social network analysis (e.g., similarity and centrality) has been proposed to improve the accuracy of the calculation task. This paper proposes a forwarding strategy based on an analysis of network topology. In the proposed strategy, each node takes a sequence of snapshots of its first-order neighbors during a warm-up period. Each node exchanges its own snapshots with each other, and then aggregates the snapshots in order to extract the network topology information. The extracted network topology is analyzed by social network analysis methods: compactness and algebraic connectivity. Forwarding decisions are made using the analysis of the features (compactness and algebraic connectivity). We present simulations using NS-2 and the home-cell community-based mobility model to show that the proposed forwarding strategy results in delay performances similar to the epidemic forwarding scheme, while maintaining reasonable network traffic. In addition, we demonstrate that the proposed strategy outperforms the SimBet and PRoPHET forwarding schemes with various communication ranges and memory space.

Software Defined Networking (SDN) is a network architecture that decouples the control and data planes. SDN enables network control to make its programmable directly. Software defined networking is the OpenFlow protocol and its architecture is designed for Local Area Networks (LAN). It does not include effective mechanisms for fast resiliency. Fast resiliency is a major requirement in metro and carrier-grade Ethernet network. The proposed scheme aims to reduce the recovery time during single link network failures. The controller calculates the backup path proactively using segment protection scheme. The switches identify link failures in segments using Bidirectional Forwarding Detection (BFD) protocol and reroute the traffic. As the link is recovered the switches will start using the best path. The controller deletes the backup segment entries when the corresponding working path entries expire. This paper experiments the link protection scheme that aims to enhance the OpenFlow architecture by adding fast recovery mechanisms in the switch and the controller. This is achieved by enabling the controller to add backup paths proactively along with the working paths and enabling the switches to perform the recovery actions locally. Recovery time is less compared to the switch-controller and round trip time which provides better results. The system performance is evaluated by finding the packet loss and switch over time by comparing it with the current OpenFlow implementations. The system performs reasonably better than the existing ones in terms of switch over time.

Software defined networking technology, centralizes and simplifies the control of network with centralized network provisioning and guaranteed content delivery. The conventional networks face link failure as its one of the major vulnerabilities that occurs within the networking topology. The paper proposes a technique to handle multiple link failure using Bidirectional Forwarding Detection(BFD). The one or more link failures occur due to slow convergence, pre-defined backup bandwidth, and loops resulting in degradation of the network performance. Widely, these failures cause paths that are not valid and reachable within wired networks. The length of every path containing an unsuccessful link is recorded and the total invalid routing time is computed. The out of reach paths record the overall range of paths that are unsuccessful during network partitioning. The multiple link failures are handled using multiple BFD sessions that are maintained by transmitting hello messages within the network. The corresponding neighbour nodes can have synchronized clock to detect failures at the same time.

5G networks offer various network services based on software defined networking and network function virtualization. However, certain services are sensitive to link latency which is why it is consistently observed to provide high quality services. Previous studies have proposed two approaches to this task: measuring the latency by probe packets and link-layer discovery protocol (LLDP) packets. However, they have several limitations like flow rule preconfiguration, influence of the control plane traffic, and necessity of calibration. In this paper, Bidirectional forwarding detection (BFD) based approach is proposed. The approach measures latency at the data plane with simply implemented echo mode in Open vSwitch. We evaluates and compare the proposed approach to LLDP-based one in terms of single link latency and path latency, and error rate. In addition, we verify that the control plane throughput affects link latency according to the increased number of switches. As a result, the proposed approach can resolve the limitations and provides accuracy link latency.

Future power grids — due to the ongoing development towards distributed, renewable generation — depend heavily on reliable real-time monitoring and control. Thus appropriate Information and Communication Technologies are crucial to guarantee stable grid operation. Software-Defined Networking is being considered for handling the diverse requirements of Smart Grid communications. In particular, simultaneous failures of power and communication systems need to be addressed nearly instantaneously (sub 10 milliseconds) to secure timely operation of critical protection functions. To evaluate such scenarios the exact time and sequence of events, in case of communication failures, need to be determined. Hence, a Smart Grid Software-Defined Networking testbed is introduced. It comprises a purpose-built hardware platform that synchronizes networking devices, allowing for highly accurate delay measurements. The platform also enables the precise interruption of communication links. It mimics the characteristics of physical link disruptions, facilitating the study of triggered effects and their time of occurrence. The resulting measurement set-up enables a conclusive comparison of different recovery approaches based on Software-Defined Networking. Finally the need for advanced failure detection mechanisms, such as Bidirectional Forwarding Detection or controller heartbeats, is shown.

We have previously proposed and implemented a novel low cost 100G transmission system which has the 1 RU only size and a small form factor [1]. In this paper we further develop a LLF (Link Loss Forward) feature which can monitor the health of this 100G system and make a necessary link failure management. The mechanism is based on the fast FPGA insertion/desertion processing and the usage of un-used overheads of OTN digital wrapper as an in-band tunneling, so that the remote link failure relay, link failure isolation, and alarm report can be done properly. Finally, when the link failure is re-covered, the system will detect it and do automatic recovery as well as alarm clearance accordingly.

The effective incentive scheme is proposed to stimulate the forwarding cooperation of nodes in VANETs. In a coalitional game model, every relevant node cooperates in forwarding messages as required by the routing protocol. This scheme is extended with constrained storage space. A lightweight approach is also proposed to stimulate the cooperation.

Named data networking (NDN) has been drawing increasing attention in academia as well as industry. Data forwarding is one of the key issues in relation to efficient content retrieval in Named Data MANETs. Existing data forwarding protocols aim at either reducing network overhead or improving the success rate of content retrieval, but not both. As both metrics are important, in this paper, we propose a Greedy and Neighbor Aware forwarding protocol (GNA) to balance the trade-offs between success ratio of content retrieval and network overhead, and make NDN suitable for arbitrarily moving nodes in MANETs. The simulation results show that, compared with the greedy forwarding protocol, the GNA protocol can increase the success ratio of content retrieval by about 50% at the lower node density, and increase the network overhead by about 30%, the larger the data packet, the smaller the gap in network overhead; the transmission delay in GNA protocol is similar as the greedy forwarding protocol.

A Named Data Networking (NDN) router can maintain a record in its PIT for every Interest packet and leverage PIT table to achieve the goal of stateful forwarding. In this paper, a more general application scene that presents new challenges for stateful forwarding is considered. The network element needs to keep states of previously forwarded packets to determine the forwarding behavior of subsequent packets. We are devoted to keeping states efficiently based on Protocol Oblivious Forwarding (POF), which is an enhancement to current OpenFlow-based SDN forwarding architecture. Specifically, we propose using Linear-Match table to keep states (LMKS) considering the performance and potential scalability. Experimental results on Linux-based POF soft switch show that LMKS can improve forwarding latency and throughput significantly with manageable processing overhead for network applications that require keeping states.

Multicast forwarding in the context of IP-MPLS networks for services like VPLS has important scalability issues. Alternatives to per-VPLS tree construction based on aggregation of multipoint requests onto shared trees have been studied. Other works have focused on stateless forwarding based on Bloom filters. Both suffer from some type of forwarding anomalies. This paper proposes the combination of both forwarding modes: shared multicast trees and an efficient variant of stateless switching based on Bloom filters. Simulations prove that constraining the forwarding to the shared tree is an effective mechanism to prevent most side effects of Bloom filter-based forwarding, making the combined technique a good trade-off in terms of forwarding state consumption, yielding best performance in terms of overhead with respect to each technique in isolation.

Network devices rely on forwarding rules to forward packets. With the latest OpenFlow standard (the de-facto software defined network standard), the rules that make up a forwarding set may be expressed in the form of a single table or multiple linked tables. This raises the question of how to reconcile the forwarding behaviour of different flow tables? In this paper we propose two approaches to convert various forwarding sets into a canonical form called equivalent forwarding set and formalise the process of evaluating equivalence between two forwarding sets in terms of networking function.

Cooperative forwarding has shown a substantial network performance improvement compared to traditional routing in multi-hop wireless networks. To further enhance the system throughput, especially in the presence of highly congested multiple cross traffic flows, a promising way is to incorporate the multi-radio multi-channel (MRMC) capability into cooperative forwarding. However, it has been said that incorporating MRMC into cooperative forwarding can be considered as a trade-off between multiplexing and spatial diversity and what choice the neighbouring nodes should make is non-trivial. In this paper, we propose a new cooperative forwarding mechanism for multi-radio multi-channel multi-flow wireless networks. The performance is studied in highly congested network and under the situation where the same set of forwarding candidates is being used for multiple flows. Performance evaluation shows that the integrated mechanism achieves about 200% of throughput improvement compared to the single-radio single-channel case.

A lot of researches exploit the flexibility of Software-Defined Networking (SDN) to conduct traffic engineering in order to improve network performance and enhance robustness to failures. As the upgrade of a traditional network to a full SDN deployment is an incremental process, the coexistence of SDN switches and legacy switches forms a hybrid SDN. Due to the different forwarding characteristics of these switches, it is essential to coordinate the forwarding of SDN control and distributed routing to avoid inconsistency and achieve high network utilization. In this paper, we note that the effectiveness of traffic engineering in hybrid SDN strongly depends on both the structures of forwarding graphs and traffic distribution, while existing approaches mainly focus on the latter. We first define the consistent forwarding graph, and then construct forwarding graphs with potential high throughput for effective traffic engineering, while maintaining forwarding consistency. The evaluation results show that the proposed forwarding graph construction approach improves network throughput and achieves better load balancing compared with existing simple forwarding path constructing approaches, especially with more fraction of SDN deployment.

Name-based forwarding is a core component in information-centric networks. Designing scalable name-based forwarding solutions is challenging because name prefixes are of variable length and the forwarding tables can be much longer than seen with IP. Recently, the speculative forwarding method has been proposed, in which the forwarding structure size is proportional to the information-theoretic differences between the name prefixes rather than their lengths. In this paper, our goal is to enhance name-based forwarding performance with memory- and time-efficient data structures. We first define the string differentiation problem, based on the behavior of speculative forwarding in core networks, and then propose fingerprint-based solutions for both trie-based and hash table-based data structures. We experimentally demonstrate that the proposed solutions reduce the lookup latency and memory requirements. The proposed fingerprint-based Patricia trie decreases the average leaf-node depth and thus reduces the lookup latency. The proposed fingerprint-based hash table design requires only 3.2 GB of memory to store 1 billion names where each name has only one name component, and the measured lookup latency of the software-based single-threaded implementation is 0.29 microseconds. What's more, the distributed forwarding scheme presented in this paper makes name-based forwarding truly scalable.

Software defined networking is a rapidly expanding networking paradigm that aims to separate the control logic from the forwarding devices. Through centralized control, network operators are able to deploy and manage more efficient forwarding strategies. Traditionally, when the network undergoes a change through maintenance, failure, or cyber attack, the centralized controller processes these events and deploys new forwarding rules reactively. This work provides a strategy that does not require a controller in order to maintain connectivity while only using features within the existing OpenFlow protocol version 1.3 or greater. In this paper we illustrate why forwarding resiliency is desired in OpenFlow networks and provide an algorithm that computes the flow entries required to achieve maximal forwarding resiliency in presence of both multiple link and controller failures on any arbitrary network.

Simulation is a common method used to examine the models and protocols before they are implemented in real systems. Vehicular networks present different characteristics which render most of their simulations inapplicable to real-world Vehicular Ad Hoc Networks. In these days, the important advancement has been made toward the realistic simulators. OMNeT++, SUMO, and Veins provide a decent way for vehicular network researchers. This paper introduces the design and implementation of data forwarding schemes in vehicular networks. We discuss the implementation of two data forwarding schemes, such as Vehicle-Assisted Data Delivery and Trajectory-Based Data Forwarding. Both are the forwarding schemes that rely on Expected Delivery Delay implementation of data forwarding schemes in vehicular networks. We discuss the implementation of two data forwarding schemes, such as Vehicle-Assisted Data Delivery and Trajectory-Based Data Forwarding. Both are the forwarding schemes that rely on Expected Delivery Delay.

Simplified forwarding schemes relying on Bloom filter (BF)-based labels emerge as a promising approach for coping with the substantial increase in lookup table memory requirements associated with the growing number of end-hosts in DataCenters. In this paper, we present for the first time the successful implementation of a BF-label forwarding scheme over a silicon photonic switch fabric and we demonstrate its functionality with 10 Gb/s data packets that carry BF-encoded labels. The optically enabled BF-label forwarding setup utilizes a Si-based 4 × 4 electro-optic switch directly controlled by an amplifier-less and digital-to-analog-converter-less high speed Field Programmable Gate Array board. The FPGA is responsible for extracting the BF-label from the incoming packets and for carrying out the BF-based forwarding function, determining the appropriate switching state towards conveying incoming packets to the desired output. The use of BF-label forwarding allows for rapid switch reconfiguration avoiding the need for large look-up table updates as the network topology changes and devices are added, removed or simply change physical location. Successful operation for 10 Gb/s data packets has been obtained for a 1 × 4 routing layout.

6LoWPAN plays a major role within the protocol stack for the future Internet of Things. Its fragmentation mechanism enables transport of IPv6 datagrams with the required minimum MTU of 1280 bytes over 802.15.4-based wireless sensor networks. With the envisioned goal of a fully standardized WSN protocol stack currently necessitating a route-over approach, i.e. routing at the IP-layer, there are two main choices for any 6LoWPAN implementation with regard to datagram fragmentation: Hop-by-hop assembly or a cross-layered direct mode, which forwards individual 6LoWPAN fragments before the whole datagram has arrived. In addition to these two straightforward approaches, we propose enhancements based on adaptive rate-restriction for the direct forwarding and a retry control for both modes to reduce the number of losses of larger datagrams. Our evaluation of the basic and enhanced forwarding modes within simulations and a hardware testbed indicate that the proposed enhancements can considerably improve packet reception rate and latency within 6LoWPAN networks.

In an opportunistic network, one of the most challenging issues is the equilibrium of the network traffic and transmission delay for forwarding messages. To resolve this problem, we propose a new forwarding scheme, called the direction entropy-based forwarding scheme (DEFS), using the main direction and direction entropy based on the information collected about the directions of the nodes in the network. Since each node sends a message to another node with a different location and less direction entropy, DEFS utilizes those nodes that are more likely to travel to various locations to forward the messages to the destination nodes. Experiments were performed on the network simulator NS-2. The results show that DEFS provides better balance than the typical forwarding schemes, such as Epidemic, PRoPHET, and WAIT. Category: Ubiquitous computing

As multimedia communications continue to grow steadily on the Internet, pipeline forwarding (PF) of packets provides a scalable solution for engineering delay-sensitive traffic while guaranteeing deterministic Quality of Service (QoS) with high resource utilization. In PF networks resource reservation, while ensuring deterministic QoS on a per-flow basis, can result in a not null blocking probability. A reservation request may fails due to enough resources being available but not during the proper time frames. This work analyses blocking probability of reservation requests since it affects the capability of utilizing network resources to carry traffic with deterministic QoS. The blocking probability and, consequently, the achievable network utilization are analytically derived on general topology PF networks as function of the traffic intensity given the traffic matrix and the network routing. The correctness of the blocking models is also assessed by simulation in different scenarios. This work represent a valuable contribution over previous analytical models of the blocking probability as their application to real size scenarios is impractical due to their computation complexity.

Graphical AbstractDisplay Omitted We design two schemes for forwarding broadcast messages in IEEE 802.16 multi-hop relay networks.The proposed schemes consider a connection identifier (CID) translation strategy.We provide the analysis of the forwarding performance.Considering CID translation will reduce the amount of resources used.Considering CID translation will reduce the transmission latency. Although the IEEE 802.16j standard introduces a connection identifier (CID)-based forwarding scheme and a tunnel-based forwarding scheme, these schemes exhibit poor performance when forwarding broadcast messages. This study considers a CID translation strategy and proposes two CID-translated forwarding schemes for IEEE 802.16 multi-hop relay networks. The basic CID-translated forwarding scheme does not require to append the relay MAC header of the tunnel-based scheme to the broadcast messages. The enhanced CID-translated forwarding scheme further divides a broadcast message into a common part and a specific part and forwards these parts in a multicast manner and a broadcast manner, respectively. Simulation results validate that the basic CID-translated forwarding scheme uses fewer resources than the tunnel-based forwarding scheme. Moreover, the enhanced CID-translated forwarding scheme outperforms the basic CID-translated forwarding scheme in terms of the system resources used and transmission latency.

We investigate the effects of two forwarding schemes, namely, random forwarding (RF) and deterministic forwarding (DF), on network lifetime in wireless sensor networks (WSNs). For the analysis of network lifetime, we construct a Markov chain model for RF and derive a closed form expression for DF. These analytic models enable identifying the conditions in which one forwarding scheme outperforms the other.

Most of existing works on the topic of real-time routing for wireless sensor networks suffer from void forwarding paths (cannot reach the destination, but have to backtrack) and time overhead of handling isolated nodes. Designing a desired real-time data forwarding protocol as well as achieving a good tradeoff between real time and energy efficiency (as well as energy balance) for delay-sensitive wireless sensor networks remains a crucial and challenging issue. In this paper, we propose an optimal query-driven data forwarding framework that each sensor gets its optimal data forwarding paths (directed acyclic graphs) based on the query messages flooded by the base station without extra overhead. Furthermore, First Forwarding Nodes and Second Forwarding Nodes schemes are developed for data forwarding. In addition, two greedy distributed data forwarding algorithms are provided base on hybrid link cost model trying to achieve energy balance and congestion avoidance in data forwarding. Our framework is fully distributed and practical to implement, as well as robust and scalable to topological changes. The extensive simulations show that our framework has significantly outperformed the existing routing protocols in terms of real time and energy efficiency.