Backup Link Research Articles

Packet Microwave Layer 1 and Layer 2 Throughput in E-band for Mobile Broadband Communications

We have more innovation on Ethernet wireless links nowadays. The introduction of the E-band and V-Band provide more spectral capacity to build microwave links with high throughput. That is done with Ethernet and MPLS in a microwave technology. In this paper we describe the evolution, application and best opportunities to use microwave in E-band frequency for the 2G/3G/4G/5G mobile networks, for fiber backup links, enterprise networks and VIP lines. We present the air link capacity, the layer 2 throughput with and without IFG and preambule suppression. The results by simulations prove the possibility to have with one channel, an air link capacity of 986 Mbps in the E-band frequency with 99.999% annual availability for path length range 0.89 km to 1.62 km in West Africa.

A 3-Parameter Routing Cost Function for Improving Opportunistic Routing Performance in VANETs

Dynamic topology and unstable wireless links make efficient data delivery in vehicular ad-hoc networks (VANETs) a challenging issue. To tackle this issue, several routing strategies for finding a route with high reliability and low latency in VANETs have been proposed. One of theme is Opportunistic routing (OR) paradigm which can improve the reliability of routing in vehicular ad-hoc networks (VANETs) by broadcasting transmission features and employing additional backup links from other neighboring nodes. In this paradigm a node sends the packet to a number of its neighbors called forwarding set. The way transmission priority is assigned to the nodes in the forwarding set can highly affect the performance of opportunistic routing. In this Paper a new measure composed of three parameters is proposed for selecting the best forwarding node. Simulations on highway environment indicate that the proposed method improves the routing performance in all grounds of QoS compared to the other published methods in the literature.

A Fault-Tolerant Deflection Routing for Network-on-Chip

Network-on-Chip (NoC) has become a promising design methodology for the modern on-chip communication infrastructure of many-core system. To guarantee the reliability of traffic, effective fault-tolerant scheme is critical to NoC systems. In this paper, we propose a fault-tolerant deflection routing (FTDR) to address faults on links and router by redundancy technique. The proposed FTDR employs backup links and a redundant fault-tolerant unit (FTU) at router-level to sustain the traffic reliability of NoC. Experimental results show that the proposed FTDR yields an improvement of routing performance and fault-tolerant capability over the reported fault-tolerant routing schemes in average flit deflection rate, average packet latency, saturation throughput and reliability by up to 13.5%, 9.8%, 10.6% and 17.5%, respectively. The layout area and power consumption are increased merely 3.5% and 2.6%.

Designs of low insertion loss optical router and reliable routing for 3D optical network-on-chip

Three-Dimensional Optical Network-on-Chip (3D ONoC) has recently emerged as a high-perfor-mance on-chip communication solution; however, owing to the intrinsic characteristics of photonic devices in existing 3D ONoC, the insertion loss caused by undesirable coupling among optical signals degrades network performance. Considering manufacturing defects and unpredictable noise sources that cause the failure of Optical Routers (ORs) in 3D ONoC, previous work simply abandoned the disabled OR when computing the restore path. In this paper, we propose a new OR structure that reduces insertion loss, and we present the design of a novel adaptive routing algorithm, FTRA-BL, based on the new OR structure with bidirectional waveguides, without abandoning any disabled ORs. Our FTRA-BL selects the normal waveguide in the disabled OR as the backup link so that the best macroscopic restore path can be guaranteed. Simulation results show that our method performs better than previous work in improving transmission reliability and latency.

λ-Augmented Tree for Robust Data Collection in Advanced Metering Infrastructure

Tree multicast configuration of smart meters (SMs) can maintain the connectivity and meet the latency requirements for the Advanced Metering Infrastructure (AMI). However, such topology is extremely weak as any single failure suffices to break its connectivity. On the other hand, the impact of a SM node failure can be more or less significant: a noncut SM node will have a limited local impact compared to a cut SM node that will break the network connectivity. In this work, we design a highly connected tree with a set of backup links to minimize the weakness of tree topology of SMs. A topology repair scheme is proposed to address the impact of a SM node failure on the connectivity of the augmented tree network. It relies on a loop detection scheme to define the criticality of a SM node and specifically targets cut SM node by selecting backup parent SM to cover its children. Detailed algorithms to create such AMI tree and related theoretical and complexity analysis are provided with insightful simulation results: sufficient redundancy is provided to alleviate data loss at the cost of signaling overhead. It is however observed that biconnected tree provides the best compromise between the two entities.

Preconfigured Ball (p-Ball) Protection Method With Minimum Backup Links for Dual-Link Failure in Optical Mesh Networks

This letter focuses on the protection method for all dual-link failures in optical mesh networks. We first state the problem and discuss the possible scenarios of dual-link failures. We then present our proposed preconfigured ball (p-Ball) protection method that provides protection against dual-link failures using fewer backup links than preconfigured cycles (p-Cycles). We propose integer linear programming to formulate the p-Ball protection method. We also propose a heuristic algorithm to find backup paths in p-Ball. Simulation results show that p-Ball is better than p-Cycle in both construction cost metrics (such as backup link number, resource redundancy, etc.) and operation cost metrics (such as average hop, protection resource utilization ratio, etc.).

Self-healing hierarchical architecture for ZigBee network in smart grid application

In this paper, by analysing the characteristics of node assignments, network structures and the data transmission in the smart grid, we propose and evaluate a self-healing hierarchical architecture SHA for the ZigBee networks in the smart grid application. The SHA could maintain the network structure based on the link quality indication LQI and the modified neighbour table information to optimise the parent child relationship from the viewpoint of overall network. A backup loop scheme is also introduced to enhance the robustness. A backup link is calculated for each node based on the network address information. The simulation results show that the SHA achieves better performance by obtaining lower average hops, lower transmitter power and less bit error rates. For the backup loop scheme, the result shows it has a greater packet delivery ratio when network topology is damaged.

LSGO: Link State aware Geographic Opportunistic routing protocol for VANETs

Abstract Robust and efficient data delivery in vehicular ad hoc networks (VANETs) with high mobility is a challenging issue due to dynamic topology changes and unstable wireless links. The opportunistic routing protocols can improve the reliability of routing by making full use of the broadcast characteristics and assist in data transmission through additional backup links. In this paper, we propose a Link State aware Geographic Opportunistic routing protocol (LSGO) which exploits a combination of geographic location and the link state information as the routing metric. The LSGO aims to improve the reliability of data transmission in a highly dynamic environment, which selects the forwarders and prioritizes them based on the vehicle’s geographic location and the link’s quality. We compare the performance of LSGO with GpsrJ + which removes the unnecessary stop at a junction and greedy traffic aware routing protocol (GyTAR) using network simulator ns-2. The simulation results show that it opens more nodes to participate in the opportunistic data forwarding and increases a connection’s throughput while using no more network capacity than traditional routing. In the simulation, compared with other two protocols, when the number of vehicles and the average vehicle velocity increase, LSGO’s packet dropping rate is reduced and the network throughput is improved.

Towards Robust Routing in Three-Dimensional Underwater Wireless Sensor Networks

The areas of three-dimensional (3D) underwater wireless sensor networks (UWSNs) have attracted significant attention recently due to their applications in detecting and observing phenomena that cannot be adequately observed by means of two-dimensional UWSNs. However, designing routing protocols for UWSNs is a challenging task because path breakage occurs frequently due to uncertain node and link failures. In this paper, we present a Robust Routing Protocol (RRP) that aims to achieve robustness under harsh underwater conditions of 3D UWSNs. In RRP, each sensor has a data structure called backup bin, which allows to construct main backup links and auxiliary backup links for repairing failed links and ensuring normal data delivery. Moreover, sensor nodes can also enlarge their transmission range to build new links when the main routing path is not reachable through backup links. Simulation results show that the proposed protocol can reduce node and link failures' impact on metrics of packet delivery ratio, network throughput, energy consumption, and average end-to-end delay.

Conceptual Framework of Redundant Link Aggregation

This is era of information blast. A huge quantity of information is pouring in from various sources. The revolutionary advancement of Information and Communication technologies bring the world close together. A pile of information in different formats is just a click away. Which motivate the organizations to get more internet bandwidth to consume and publish the information over exploding cloud of Internet. The standard router redundancy protocol is used to handle backup links however it cannot aggregate them. Whereas the link standard aggregation protocol can aggregate the link but it support only Ethernet technology. In this research paper a concept of Redundant Link Aggregation (RLA) is proposed. RLA can aggregate and handle backup links with main links regardless of carrier technology. Furthermore a data forwarding mechanism Odd Load Balancing (OLB) is also proposed for RLA scheme. For the sake of performance evaluation, Redundant Link Aggregation (RLA) is compared with Virtual Router Redundancy Protocol (VRRP). The simulation result reveals that Redundant Link Aggregation (RLA) can cover the bandwidth demand of the network in peak hours by consuming backup links as well which with Virtual Router Redundancy Protocol (VRRP) cannot. It is further noted that Odd Load Balancing (OLB) feature can be used to save the cost in terms of money per annum.

Designing of high-speed inter-building connectivity by free space optical link with radio frequency backup

This study presents the design of high-speed inter-building connectivity in medical services by free-space optical (FSO) link with wireless backup, which will operate at gigabit rates. The two buildings in medical campus are ∼500 m apart. The FSO link normally uses 1550 nm wavelength but has a radio frequency (RF) link operating at 2.4 GHz as the back-up. In this, 99.999% availability is achieved by combining the optical laser beam with an alternate path RF solution. The laser beam of 1550 nm provides high-bandwidth connectivity in majority of the time, whereas the RF path maintains critical network connectivity during extreme weather events that are detrimental to the FSO link, such as thick fog. Optical wireless links suffer from atmospheric loss mainly because of fog, scintillation and precipitation. The authors investigate here the impact of fog, rain and snow effects and evaluate their performances for the optical propagation through the atmosphere. The wireless back-up link is used only in very dense fog conditions. Hybrid FSO/RF systems have also been examined as a means to provide high-bandwidth point-to-point links in the access network over larger distances.

Improvement of BGP Session Maintenance

In the early days, the Internet used static routes, but very quickly network administrators couldnt keep manually updating their routing tables. Later, Internet network administrator used a protocol called EGP but EGP was not scalable so BGP was introduced to solve all problems and more. BGP stands for Border Gateway Protocol and the most current version is BGP4. BGP is a routing protocol that runs on routers. BGP allows fully decentralized management of the Internet. That means, if BGP router is on the Internet, it can tell all other routers that what networks are available to everyone in the world. BGP calls each routing domain an autonomous system (AS). It selects the best path, through the Internet, by choosing the route that has to traverse the fewest autonomous systems. As BGP provides information for controlling the flow of packets between ASes, the protocol plays a critical role in Internet efficiency, reliability, and security. However, slow convergence and abnormal termination of session are major vulnerability of BGP. Simplifying BGP design complexity helps in research, for the root cause analysis of BGP. Deriving technique to prevent the loss of data, reduce the convergence time and maintaining the sessions of BGP by instantly diverting the traffic from teardown / flapped link to the backup link considering as active link. It will be a great success to achieve the goal to maintain the sessions and reduce the BGP convergence time.

Comparison of link selection algorithms for free space optics/radio frequency hybrid network

The great potential of free space optics (FSO) communication motivates to use it for future requirement of high bandwidth links. However, the widespread use of this technology has been hampered by the reduced availability because of weather effects. To overcome these shortcomings a back-up link can be used so that the combined hybrid network may achieve carrier class availability. A hybrid, FSO/wireless LAN (WLAN) self-synchronising architecture is presented, which provides transparent connectivity without protocol overhead. The switching from one link to another needs efficient algorithms to achieve the optimal bandwidth utilisation while maintaining availability. Generally, the received signal strength is considered as a parameter for switching between the links. In this study, link selection has been analysed for a variety of algorithms, including filtering and hysteresis, using measured data of fog events. The combination of time and power hysteresis is found to be the optimum solution.

LIB: A Last-In-Backup Based Fast Recovery Scheme for Ring-Based Industrial Networks

Ring-based industrial networks must possess a fast recovery algorithm when either the switch node or link is faulty. This work presents a simple yet extremely fast recovery algorithm based on the last-in-backup (LIB) concept, in which the final link added to the ring is the backup link. Analysis results indicate the proposed LIB algorithm performs significantly better than the MRP protocol developed in the latest version of the IEC 62439 standard. The proposed LIB algorithm is implemented in industrial Ethernet switches as well. Our results further demonstrate that the proposed recovery algorithm is extremely feasible with a link-down recovery time of 5.5 ms for 50 switches and 6.5ms for 250 switches.

Performance Analysis of Throughput Efficient Switch-over between FSO and mmW Links

Free Space Optics (FSO) links provide usage of high bandwidth and the flexibility of wireless communication links. However, weather patterns like fog and heavy snow fall limit the availability of FSO. Another technology providing similar properties regarding offered data rates and flexibility of setup is Millimeter Wave Technology (mmW), operating at several tens of GHz. In this case, heavy rain limits mmW link availability. A combination of both technologies had been proved to be very effective to achieve very high availability. Different hybrid architectures of these two links and switch-over techniques had been proposed in the recent years. All of these techniques require redundant transmission on either both transmission links or waste bandwidth of backup link when main FSO link is operational. In this paper, a switch-over between these technologies is proposed, to maintain high availability without the loss of transmission bandwidth. The performance of this switch-over has been simulated for more than one year measured availability data for hybrid network of mmW link and FSO link. The switch over behavior has also been simulated for fog, rain and snow events. It has been shown that the availability with switch-over reaches the redundant link availability but switchover can save more than 90% redundant transmission and increase the hybrid network throughput significantly.

Dynamic resource sharing protection using label stacking and burst multiplexing in optical burst switched networks

A protection and restoration mechanism is essential to provide reliable traffic transmission in networks, but it is not easy to apply existing protection mechanisms to optical burst-switching (OBS) networks, because of the unique properties of OBS. The authors introduce a 1:1 link-based protection that minimises burst losses by deflecting bursts until a source ingress router arbitrates a working path to a backup path when a link failure occurs. The authors also propose a genuine dynamic resource sharing (DRS) link protection in order to achieve high efficiency in network resource allocation and reliable protection simultaneously in OBS networks. DRS employs burst-multiplexing and label-stacking techniques in backup channel selection and always reserves an optimal number of backup channels according to the changes in traffic load in a working link and the quality of service (QoS) requirements of bursts. Simulation results show that the DRS can provide the same protection reliability with just half of the backup channels needed in a normal 1:1 protection in a light-load case, while guaranteeing the QoS requirements of class bursts. The authors show that this property also makes backup link sharing among a number of working links possible.

Fairness of sharing protection for multicast in WDM networks

In this paper, the sharing schemes of multicast in survivable Wavelength-Division Multiplexed (WDM) networks are studied and the concept of Shared Risk Link Group (SRLG) is considered. While the network resources are shared by the backup paths, the sharing way is possible to make the backup paths selfish. This selfishness leads the redundant hops of the backup route and a large number of primary lightpaths to share one backup link. The sharing schemes, especially, the self-sharing and cross-sharing, are investigated to avoid the selfishness when computing the backup light-tree. In order to decrease the selfishness of the backup paths, it is important to make the sharing links fair to be used. There is a trade-off between the self-sharing and cross-sharing, which is adjusted through simulation to adapt the sharing degree of each sharing scheme and save the network resources.

Preemption rates for a parallel link loss network

We consider a two parallel link network supporting K call classes, where a class k call may preempt if necessary any calls of classes k + 1 , … , K , and may in turn be preempted by any calls of class 1 , … , k − 1 . The two links are a (preferred) primary link (PL) and a backup link (BL). The preemption policy permits both preemption from the PL to the BL (a transfer) if possible, and eviction from either link if necessary. We characterize the rates of an arriving class k call causing preemption of an active lower priority call, and of an active class k call being preempted by an arriving higher priority call. When all classes share a common service rate, we express the preemption rates for each class in terms of the Erlang-B blocking probability equation. Simple expressions for the preemption rates are obtained in the heavy traffic limit. When classes have individual service rates, we approximate the preemption rates for each class using nearly completely decomposable (NCD) Markov chain techniques. The accuracy of the approximation improves with increasing timescale separation between classes.

Joint resource conserving and load distributing approaches for routing of survivable connections

This paper investigates the problem of on-line routing of bandwidth guaranteed paths with end-to-end restoration. We first present the characteristic of bandwidth sharing on backup paths for varying degrees of network state information. We also propose a new Partial Information Scenario (PIS) in which the propagated state information is judiciously selected, such that the protocol overhead remains identical to that of the original PIS. Then, an iterative variant of two-step routing approach is used to compute link–disjoint active and backup paths. In order to implement this restorable routing, we consider a new class of weight function as the choice of cost metric. Generally, there are two schools of thought regarding the choice of link cost: resource conserving and load distributing. This paper suggests the use of both approaches for calculating active and backup link costs, to simultaneously achieve an economical usage of resources and efficient distribution of traffic load on the network. Comparing with the existing best-known algorithms, we show that our method outperforms the others with respect to the number of rejected requests as well as the total bandwidth consumption. Moreover, it has a much shorter running time, which makes it more attractive for on-line routing.

Dual-Link Failure Resiliency Through Backup Link Mutual Exclusion

Networks employ link protection to achieve fast recovery from link failures. While the first link failure can be protected using link protection, there are several alternatives for protecting against the second failure. This paper formally classifies the approaches to dual-link failure resiliency. One of the strategies to recover from dual-link failures is to employ link protection for the two failed links independently, which requires that two links may not use each other in their backup paths if they may fail simultaneously. Such a requirement is referred to as backup link mutual exclusion (BLME) constraint and the problem of identifying a backup path for every link that satisfies the above requirement is referred to as the BLME problem. This paper develops the necessary theory to establish the sufficient conditions for existence of a solution to the BLME problem. Solution methodologies for the BLME problem is developed using two approaches by: 1) formulating the backup path selection as an integer linear program; 2) developing a polynomial time heuristic based on minimum cost path routing. The ILP formulation and heuristic are applied to six networks and their performance is compared with approaches that assume precise knowledge of dual-link failure. It is observed that a solution exists for all of the six networks considered. The heuristic approach is shown to obtain feasible solutions that are resilient to most dual-link failures, although the backup path lengths may be significantly higher than optimal. In addition, the paper illustrates the significance of the knowledge of failure location by illustrating that network with higher connectivity may require lesser capacity than one with a lower connectivity to recover from dual-link failures.