Showing papers on "Anycast published in 2019"

Zone Probabilistic Routing for Wireless Sensor Networks

Abstract: This article modeled the data routing problem in Wireless Sensor Networks as an in-zone random process. The data packets are randomly routed from the source to the sink within the defined Routing Zone via any-path . The proposed “Zone Probabilistic Routing (ZPR)” is a distributed probabilistic and randomized anycast routing protocol. In ZPR, the forwarding probability distribution is defined by multiplying the Four Probability Distributions (4PD) namely: direction, transmission distance, perpendicular distance, and residual energy. In order to meet different performance requirements for different applications, these probability distributions are completely controllable via a set of exponential control-parameters (direction control, transmission distance control, perpendicular distance control, and residual energy control). This set of parameters is user-oriented and can be modified prior to nodes deployment to achieve different performances. Through extensive simulations and experimental results, the optimal values for these exponential control-parameters have been obtained to meet different performance requirements in terms of energy consumption, energy balancing, network lifetime, and delay. Furthermore, through an extensive performance evaluation study and simulation of large-scale scenarios, the results showed that our proposed ZPR protocol achieved better performance compared to the state-of-the-art solutions in terms of network lifetime, energy consumption, and data routing efficiency.

Learning for adaptive anycast in vehicular delay tolerant networks

Abstract: We propose a protocol for vehicular delay tolerant networks (DTN) with special focus on anycast communications from a vehicle to the cloud where multiple gateways (such as road side units) exist. The protocol employs a Q-learning algorithm to estimate the multi-hop destination encounter probability by discounting the reward with the number of forwards (number of hops). Anycast encounter probability is maintained in a specific entry which considers multiple gateways as the same virtual destination. The proposed protocol also uses an adaptive data replication scheme to take into account the destination encounter probability and the relative velocity between vehicles jointly, which can achieve a high data delivery ratio and low overhead. We use computer simulations to evaluate the proposed protocol.

Taming Anycast in the Wild Internet

Abstract: Anycast is a popular tool for deploying global, widely available systems, including DNS infrastructure and content delivery networks (CDNs). The optimization of these networks often focuses on the deployment and management of anycast sites. However, such approaches fail to consider one of the primary configurations of a large anycast network: the set of networks that receive anycast announcements at each site (i.e., an announcement configuration). Altering these configurations, even without the deployment of additional sites, can have profound impacts on both anycast site selection and round-trip times.In this study, we explore the operation and optimization of any-cast networks through the lens of deployments that have a large number of upstream service providers. We demonstrate that these many-provider anycast networks exhibit fundamentally different properties when interacting with the Internet, having a greater number of single AS hop paths and reduced dependency on each provider, compared with few-provider networks. We further examine the impact of announcement configuration changes, demonstrating that in nearly 30% of vantage point groups, round-trip time performance can be improved by more than 25%, solely by manipulating which providers receive anycast announcements. Finally, we propose DailyCatch, an empirical measurement methodology for testing and validating announcement configuration changes, and demonstrate its ability to influence user-experienced performance on a global anycast CDN.

Fast multi-hop broadcast of alert messages in VANETs: An analytical model

Abstract: Recent market trends in self-driving technology have revived the attention on vehicular networks, posing a demand for intelligent solutions supporting the proliferation of many useful applications. Inter-vehicular communication presents an opportunity, capable of providing the basis for localized, timely, collective intelligence. In this context, critical safety applications are particularly challenging, urging for quick multi-hop message propagation schemes within an area of interest. The anycast communication model embodied by safety applications and the shared broadcast medium demand for intelligent message propagation schemes minimizing latency. To this end, the state of the art approach is based on having different contention windows among vehicles so as to probabilistically select specific ones as forwarders in order to reduce the number of hops and transmissions needed to propagate the message. However, this solution has been mainly studied empirically. In this article, we present and discuss an analytical model, shedding light on the expected behavior and performance of such approach, along with a validation analysis conducted through the well known simulator NS-2.

Asymmetric network elements sharing an anycast address

Abstract: For a managed network implementing at least one logical router having centralized and distributed components, some embodiments provide a method that better supports the provision of certain network applications and/or services. The method receives at a host implementing (1) a distributed logical router and (2) a plurality of logical switches of a logical network along with other hosts, a message from a first data compute node (DCN) executing on the host. The host logically forwards the message to the distributed logical router that uses a particular anycast internet protocol (IP) address using a first media access control (MAC) address. The distributed router determines that the message requires processing by a centralized logical router (e.g., a service router, edge node, etc.) executing on an edge node host and forwards the message to the centralized logical router using the same anycast IP address and a second, unique MAC address.

Inferring Catchment in Internet Routing

Abstract: BGP is the de-facto Internet routing protocol for interconnecting Autonomous Systems (AS). Each AS selects its preferred routes based on its routing policies, which are typically not disclosed. Due to the distributed route selection and information hiding, answering questions such as "what is the expected catchment of the anycast sites of a content provider at the AS-level, if new sites are deployed?", or "how will load-balancing behave if an ISP changes its routing policy for a prefix?", is a hard challenge. In this work, we propose a framework and methodology to infer the routing behavior in existing or hypothetical routing configurations, and provide new capabilities and insights for informative route inference (e.g., isolating the effect of randomness that is present in prior simulation-based approaches). The proposed framework can be useful in a number of applications: measurements/monitoring, traffic engineering, network planning, Internet routing models, etc.

Towards passive analysis of anycast in global routing: unintended impact of remote peering

Abstract: Anycast has been widely adopted by today's Internet services, including DNS, CDN, and DDoS protection, in which the same IP address is announced from distributed locations and clients are directed to the topologically-nearest service replica. Prior research has focused on various aspects of anycast, either its usage in particular services such as DNS or characterizing its adoption by Internet-wide active probing methods. In this paper, we first explore an alternative approach to characterize anycast based on previously collected global BGP routing information. Leveraging state-of-the-art active measurement results as near-ground-truth, our passive method without requiring any Internet-wide probes can achieve 90% accuracy in detecting anycast prefixes. More importantly, our approach uncovers anycast prefixes that have been missed by prior datasets based on active measurements. While investigating the root causes of inaccuracy, we reveal that anycast routing has been entangled with the increased adoption of remote peering, a type of layer-2 interconnection where an IP network may peer at an IXP remotely without being physically present at the IXP. The invisibility of remote peering from layer-3 breaks the assumption of the shortest AS paths on BGP and causes an unintended impact on anycast performance. We identify such cases from BGP routing information and observe that at least 19.2% of anycast prefixes have been potentially impacted by remote peering.

Deterministic traffic management in an anycast network

Abstract: A two-tier Anycast addressing hierarchy enables deterministic traffic management in an Anycast system. Different locations of the Anycast system advertise a common Anycast cover route comprising a first-tier Anycast address with a first address prefix, and different specific routes comprising a set of second-tier Anycast addresses with a second address prefix, wherein each address of the set of second-tier Anycast addresses falls within the already advertised Anycast cover route, and wherein the second prefix is larger than the first prefix. Domain Name System (DNS) operation can resolve queries to the cover route when normal Anycast operation is desired or can be modified to resolve a subset of queries to a particular second-tier address in order to shift a deterministic amount of traffic based on the resolved subset of queries to a deterministically selected Anycast system location based on the location from which the particular second-tier address is advertised.

The Minimum Cost D-Geodiverse Anycast Routing with Optimal Selection of Anycast Nodes

Abstract: Consider a geographical network with associated link costs. In anycast routing, network nodes are partitioned into two sets - the source nodes and the anycast (destination) nodes - and the traffic of each source node is routed towards the anycast node providing the minimum routing cost path. By considering a given geographical distance parameter D, we define an anycast routing solution as D-geodiverse when for each source node there are two routing paths, each one towards a different anycast node, such that the geographical distance between the two paths is at least D. Such a solution has the property that any disaster with a coverage diameter below $D$ affecting one routing path (but without involving neither the source node nor its entire set of outgoing links) cannot affect the other path, enhancing in this way the network robustness to natural disasters. The selection of the anycast nodes has an impact both on the feasibility and cost of a D- geodiverse anycast routing solution. Therefore, for a desired number of anycast nodes R, we define the minimum cost D- geodiverse anycast problem (MCD-GAP) aiming to identify a set of $R$ anycast nodes that obtain a minimum cost routing solution. The problem is defined based on integer linear programming and is extended to consider the existence of vulnerability regions in the network, i.e., by imposing the geographical distance $D$ only between network elements belonging to the same region. We present computational results showing the tradeoff between $D$ and $R$ in the optimal solutions obtained with and without vulnerability regions.

Evaluating performance and inefficient routing of an anycast CDN

Abstract: Anycast has been increasingly deployed for content delivery networks to map clients to their nearby replicas, which relies on the underlying routing. However, the simplicity of operation comes at cost of less precise client-mapping control. Although many works have measured anycast DNS, anycast CDNs, with different service goals and engineering, are still not fully understood. In this paper, we design novel methods and combine large-scale traceroute and HTTP measurement to evaluate the overall client-proximity and inefficient routing of the largest anycast CDN, Cloudflare. We find that 90% paths traverse only 2-4 ASes, which highlights its direct networks providers. By further identifying and characterizing direct providers at finer granularity of facilities, we quantitatively shows that Cloudflare unevenly uses few large transit providers to delivery the majority of contents. Inspired by the observations, we propose an anycast routing pathology and diagnosis methodology. Investigation reveals that few huge providers have outsized impact in that they are not only related to many inter-domain inflations, but also have path inflation inside their own networks, thus deserving priority focus when troubleshooting.

Artemis: A Practical Low-latency Naming and Routing System

Abstract: Today, Internet service deployment is typically implemented with server replication at multiple locations for the purpose of load balancing, failure tolerance, and user experience optimization. Domain name system (DNS) is responsible for translating human-readable domain names into network-routable IP addresses. When multiple replicas exist, upon the arrival of a query, DNS selects one replica and responds with its IP address. Thus, the delay caused by the process of DNS query including the selection of replica is part of the connection setup latency. In this paper, we proposed Artemis, a practical low-latency naming and routing system that aims at reducing the connection setup latency by eliminating the DNS query latency while keeping the ability to perform optimal server (replica) selection based on user-defined rules. Artemis achieves these goals by integrating name resolution into the transport layer handshake. Artemis allows clients to calculate locally the IP address of a Service Dispatcher, which serves as a proxy of hosting servers. Service Dispatchers forward the handshake request from a client to a server, and the response is embedded with the server's IP address back to the client. This enables clients to connect directly with servers afterward without querying DNS servers, and therefore eliminates the DNS query latency. Meanwhile, Artemis supports user-defined replica selection policies. We have implemented Artemis and evaluated its performance using the PlanetLab testbed and RIPE Atlas probes. Our results show that Artemis reduces the connection setup latency by 26.2% on average compared with the state-of-the-art.

Optimizing traffic paths to orphaned hosts in VXLAN networks using virtual link trunking-based multi-homing

Abstract: Embodiments are directed to a process and system for optimizing traffic paths for orphaned hosts in a VXLAN system, by configuring virtual link trunking (VLT) peers to advertise MAC addresses learned from all multi-homed hosts in the system using Anycast VXLAN tunnel endpoint-Internet Protocol address (VTEP-IP); configuring the virtual link trunking (VLT) peers to advertise MAC addresses learned from all single-homed hosts in the system using a secondary VTEP-IP; directing unicast traffic destined to the single-homed hosts to directly connected VLT peers using the Secondary VTEP-IP; and directing Broadcast, unknown unicast, and multi-cast (BUM) traffic destined to the single-homed hosts to directly connected VLT peers using the Inclusive Multicast Ethernet Tag route.

Inferring Catchment in Internet Routing

Abstract: BGP is the de-facto Internet routing protocol for exchanging prefix reachability information between Autonomous Systems (AS). It is a dynamic, distributed, path-vector protocol that enables rich ex...

A Report on Compute First Networking (CFN) Field Trial

Abstract: Compute First Networking (CFN) enables the routing of the service request to an optimal edge site to improve the overall system load balancing and efficiency. Especially when an edge site is overloaded, other edges with service equivalency can dynamically serve the request. This document describes a CFN field trial to show the effect that CFN can achieve. Edge to edge interaction to get the available computing resources information for services and the network status to each other is introduced. Data plane to support late binding based dynamic anycast is illustrated too. The field trial shows that CFN can greatly improve the overall query per second served for a service hosted on multiple edges in a more balanced way.

Inferring Catchment in Internet Routing

Abstract: BGP is the de-facto Internet routing protocol for exchanging prefix reachability information between Autonomous Systems (AS). It is a dynamic, distributed, path-vector protocol that enables rich expressions of network policies (typically treated as secrets). In this regime, where complexity is interwoven with information hiding, answering questions such as "what is the expected catchment of the anycast sites of a content provider on the AS-level, if new sites are deployed?", or "how will load-balancing behave if an ISP changes its routing policy for a prefix?", is a hard challenge. In this work, we present a formal model and methodology that takes into account policy-based routing and topological properties of the Internet graph, to predict the routing behavior of networks. We design algorithms that provide new capabilities for informative route inference (e.g., isolating the effect of randomness that is present in prior simulation-based approaches). We analyze the properties of these inference algorithms, and evaluate them using publicly available routing datasets and real-world experiments. The proposed framework can be useful in a number of applications: measurements, traffic engineering, network planning, Internet routing models, etc. As a use case, we study the problem of selecting a set of measurement vantage points to maximize route inference. Our methodology is general and can capture standard valley-free routing, as well as more complex topological and routing setups appearing in practice.

DDoS Attack Mitigation through Root-DNS Server: A Case Study

Abstract: Load balancing and IP anycast are traffic routing algorithms used to speed up delivery of the Domain Name System. In case of a DDoS attack or an overload condition, the value of these protocols is critical, as they can provide intrinsic DDoS mitigation with the failover alternatives. In this paper, we present a methodology for predicting the next DNS response in the light of a potential redirection to less busy servers, in order to mitigate the size of the attack. Our experiments were conducted using data from the Nov. 2015 attack of the Root DNS servers and Logistic Regression, k-Nearest Neighbors, Support Vector Machines and Random Forest as our primary classifiers. The models were able to successfully predict up to 83% of responses for Root Letters that operated on a small number of sites and consequently suffered the most during the attacks. On the other hand, regarding DNS requests coming from more distributed Root servers, the models demonstrated lower accuracy. Our analysis showed a correlation between the True Positive Rate metric and the number of sites, as well as a clear need for intelligent management of traffic in load balancing practices.

Improving Anycast with Measurements

Abstract: Since the first Distributed Denial-of-Service (DDoS) attacks were launched, the strength of such attacks has been steadily increasing, from a few megabits per second to well into the terabit/s range. The damage that these attacks cause, mostly in terms of financial cost, has prompted researchers and operators alike to investigate and implement mitigation strategies. Examples of such strategies include local filtering appliances, Border Gateway Protocol (BGP)-based blackholing and outsourced mitigation in the form of cloud-based DDoS protection providers. Some of these strategies are more suited towards high bandwidth DDoS attacks than others. For example, using a local filtering appliance means that all the attack traffic will still pass through the owner's network. This inherently limits the maximum capacity of such a device to the bandwidth that is available. BGP Blackholing does not have such limitations, but can, as a side-effect, cause service disruptions to end-users. A different strategy, that has not attracted much attention in academia, is based on anycast. Anycast is a technique that allows operators to replicate their service across different physical locations, while keeping that service addressable with just a single IP-address. It relies on the BGP to effectively load balance users. In practice, it is combined with other mitigation strategies to allow those to scale up. Operators can use anycast to scale their mitigation capacity horizontally. Because anycast relies on BGP, and therefore in essence on the Internet itself, it can be difficult for network engineers to fine tune this balancing behavior. In this thesis, we show that that is indeed the case through two different case studies. In the first, we focus on an anycast service during normal operations, namely the Google Public DNS, and show that the routing within this service is far from optimal, for example in terms of distance between the client and the server. In the second case study, we observe the root DNS, while it is under attack, and show that even though in aggregate the bandwidth available to this service exceeds the attack we observed, clients still experienced service degradation. This degradation was caused due to the fact that some sites of the anycast service received a much higher share of traffic than others. In order for operators to improve their anycast networks, and optimize it in terms of resilience against DDoS attacks, a method to assess the actual state of such a network is required. Existing methodologies typically rely on external vantage points, such as those provided by RIPE Atlas, and are therefore limited in scale, and inherently biased in terms of distribution. We propose a new measurement methodology, named Verfploeter, to assess the characteristics of anycast networks in terms of client to Point-of-Presence (PoP) mapping, i.e. the anycast catchment. This method does not rely on external vantage points, is free of bias and offers a much higher resolution than any previous method. We validated this methodology by deploying it on a testbed that was locally developed, as well as on the B root DNS. We showed that the increased \textit{resolution} of this methodology improved our ability to assess the impact of changes in the network configuration, when compared to previous methodologies. As final validation we implement Verfploeter on Cloudflare's global-scale anycast Content Delivery Network (CDN), which has almost 200 global Points-of-Presence and an aggregate bandwidth of 30 Tbit/s. Through three real-world use cases, we demonstrate the benefits of our methodology: Firstly, we show that changes that occur when withdrawing routes from certain PoPs can be accurately mapped, and that in certain cases the effect of taking down a combination of PoPs can be calculated from individual measurements. Secondly, we show that Verfploeter largely reinstates the ping to its former glory, showing how it can be used to troubleshoot network connectivity issues in an anycast context. Thirdly, we demonstrate how accurate anycast catchment maps offer operators a new and highly accurate tool to identify and filter spoofed traffic. Where possible, we make datasets collected over the course of the research in this thesis available as open access data. The two best (open) dataset awards that were awarded for these datasets confirm that they are a valued contribution. In summary, we have investigated two large anycast services and have shown that their deployments are not optimal. We developed a novel measurement methodology, that is free of bias and is able to obtain highly accurate anycast catchment mappings. By implementing this methodology and deploying it on a global-scale anycast network we show that our method adds significant value to the fast-growing anycast CDN industry and enables new ways of detecting, filtering and mitigating DDoS attacks.

Sociocast: Design, Implementation and Experimentation of a New Communication Method for the Internet of Things

Abstract: Today, Internet can support the following data delivery schemes: unicast, multicast, broadcast, and anycast, according to the way in which the endpoints of the information exchanges are identified. However, several reasons exist discouraging network operators to actually offer all such data delivery schemes to end users. As a result, application developers can rely on unicast communications only and more complex group-based data dissemination policies are implemented as part of specific applications and services and through additional patches to the basic Internet implementation. Group-based communications are crucial in several Internet of Things (IoT) application scenarios. Therefore, in this paper a new data delivery scheme called sociocast is proposed, which can be safely offered to end users. In sociocast communication, endpoints are dynamically determined based on their mutual positions in a social network built by IoT nodes according to the Social Internet of Things paradigm. In this paper, it will be shown how sociocast can be utilized to address several networking needs.

Is Link-Layer Anycast Scheduling Relevant for IEEE 802.15.4-TSCH Networks?

Abstract: With the wide adoption of low-power wireless transmissions, industrial networks have started to incorporate wireless devices in their communication infrastructure. Anycast is a link-layer technique to improve the reliability when using lossy links. Several receivers are associated to a single transmission, so that a transmission is considered erroneous when none of the receivers was able to decode and acknowledge it. Appropriately exploited by the routing layer, we can also increase the fault-tolerance. However, most of existing anycast schemes have been evaluated by simulations. Besides, most evaluation models assume that packet drops are independent events, which may not be the case for packet drops due to e.g. external interference. Here, we use a large dataset obtained from an indoor testbed to assess the gain of using anycast in real conditions. We also propose a strategy to select the set of forwarding nodes: they must increase the reliability by maintaining packet losses as independent as possible. Based on our experimental dataset, we demonstrate the efficiency of anycast, provided that next hop selection follows a specific set of rules at the routing layer.

Spread of Anycast and GSLB

Abstract: Content Delivery Networks (CDN) are regarded as important internet infrastructure that supports business on the Internet. Network latency has been identified as an important metric to improve the quality of service (QoS) of CDNs. Given the limitations to response times because of the geographic distance between servers and end-users, CDN providers have developed architectures such as Global Server Load Balancing (GSLB) and IP Anycast to realize fast responses. This study investigates how GSLB and IP Anycast contribute towards improving QoS from the users' perspective. User traffic in the campus network was analyzed and it was found that: 1) 88% of the traffic reaps the benefits of well operated internet services, i.e., they have a Round-Trip Time (RTT) of less than 100 milliseconds. 2) Although GSLB is still the primary architecture for realizing fast responses, IP Anycast supports 5.8% of the traffic.

Distributed Function Chaining with Anycast Routing

Abstract: Current networks more and more rely on virtualized middleboxes to flexibly provide security, protocol optimization, and policy compliance functionalities. As such, delivering these services requires that the traffic be steered through the desired sequence of virtual appliances. Current solutions introduce a new logically centralized entity, often called orchestrator, needing to build its own holistic view of the whole network so to decide where to direct the traffic. We advocate that such a centralized orchestration is not necessary and that, on the contrary, the same objectives can be achieved by augmenting the network layer routing so to include the notion of service and its chaining. In this paper, we support our claim by designing such a system called NFV Router. We also present an implementation and an early evaluation, showing that we can easily steer traffic through available resources. The proposed approach offers as well valuable features such as incremental deploya-bility, multi-domain service chaining, failure resiliency, and easy maintenance.

A RMSA Algorithm Resilient to Multiple Node Failures on Elastic Optical Networks

Abstract: An Elastic Optical Network (EON) provides a lot of flexibility on the way an optical network supports the demands of multiple services. This flexibility is given by the Routing, Modulation and Spectrum Assignment (RMSA) algorithm whose primary goal is to use the spectrum resources of the network in an efficient way. Recently, large-scale failures are becoming a concern and one source of such failures is malicious human activities. In terrorist attacks, although node shutdowns are harder to realize than link cuts, they are the most rewarding in the attackers' perspective since the shutdown of one node also shuts down all its connected links. In order to obtain a RMSA algorithm resilient to multiple node failures, we propose the use of a path disaster availability metric which measures the probability of each path not being affected by a multiple node failure. We present computational results considering a mix of unicast and anycast services in 3 well-known topologies. We assess the trade-off between spectrum usage efficiency and resilience to multiple node failures of our proposal against other previous known algorithms. The results show that the RMSA decision is always better when the disaster path availability metric is used. Moreover, the best way to use the path disaster availability metric in the RMSA decision depends on the traffic load of the EON.

Visualizing the Performance of an Anycast Network

Abstract: An interactive data visualization has been built that can visualize how an anycast network is functioning. Numerous interaction techniques have been utilized to allow the user to view, explore and analyze the data such that unusual routing patterns and deficiencies of the Border Gateway Protocol can be detected. The development of the project has been based on the human-centered design process making use of multiple iteration cycles. In each cycle a prototype was built and evaluated after which the received feedback was prioritized accordingly and taken in to account for the next iteration cycle. The final implementation supports drilling down in to the data such that the distribution of the queries can be viewed per continent, country, anycast site and autonomous system.

Deploying Lightweight Anycast Services Based-on Explicit Multicast Routing for Evolved Internet

Abstract: As a one-to-one-of-many communication method, anycast provides a dependable service framework for clients to select one of the nearest servers in an anycast group in evolved Internet. Deploying the Internet-scale application-layer anycast is proven to be infeasible unless the scalability issues are satisfied. To handle these challenges, we focus on application-layer anycast. Proposed framework is a comprehensive solution which allows an anycast service has its unique domain-name (a.k.a FQDN), which is associated to multiple replicated servers' unicast addresses in the worldwide. With DNS query/reply service, and through Explicit Multicast (Xcast)-based replica probing, ranking, and selection procedures, clients finally reach the nearby server. Compared to previous works, proposed solution has lowered the address resolution latency, replica probing latency, connection establishment latency, and signaling cost, while simplifying the anycast deployment by having it use a large number of medium-scale anycast groups. Besides, the deployment complexity of both anycast clients and servers, are expected reduction.

Method and device for protecting based on an anycast address

Abstract: The invention discloses a method and device for protecting based on an anycast address, and the method comprises the steps: configuring the same anycast address and anycast address field label for each domain boundary node which forms redundancy protection, and notifying the anycast address and the anycast address field label to a neighbor node of the domain boundary node; after receiving the anycast address and the anycast address field label, enabling the neighbor node adjacent to the domain boundary node to create packet forwarding contained in each domain boundary node, setting the forwarding information to one main domain boundary node as an active state, and setting the forwarding information to a standby domain boundary node as an inactive state; And in the message forwarding period, if the neighbor node detects that the forwarding information to the main domain boundary node is invalid, activating the forwarding information to a standby domain boundary node to be in an active state, so that the forwarding information to the standby domain boundary node can be used for packet forwarding.

Message sending method and device

Abstract: The invention provides a message sending method. The method is applied to a network based on anycast service. The network comprises a client device and an anycast server cluster, wherein the anycast server cluster comprises at least two servers, the at least two servers have the same internet IP anycast address, and the method comprises the following steps: the client device obtains an internet protocol IP anycast address of the anycast server cluster and an IP unicast address of the target server; the client device generates an IP detection message, wherein the IP detection message is used for detecting whether the IP anycast address of the target server is reachable or not, and the IP detection message comprises the IP anycast address and the IP unicast address of the target server, andinstructs the target server to replace the IP unicast address of the target server with the IP anycast address; and the client device sends the IP detection message to the target server. The IP anycast address accessibility of the specified anycast server can be accurately detected.

On the Complexity of RSSA of Anycast Demands in Spectrally-Spatially Flexible Optical Networks.

Abstract: Spectrally-spatially flexible optical networks (SS-FONs) are proposed as a solution to overcome the expected capacity crunch caused by the rapidly growing overall Internet traffic. SS-FONs combine two network technologies, namely, flex-grid optical networks and spatial division multiplexing yielding a significant capacity increase. Moreover, network services applying anycast transmission are gaining popularity. In anycasting, the same content is provided in several geographically spread data centers (DCs), and the requested content is delivered to the network client from themost convenient DC, e.g., minimizing the network traffic and delay. The main optimization challenge in SS-FONs is routing, spectrum and space allocation (RSSA) problem, which can be solved using integer linear programming (ILP). The main goal of this paper is to compare the complexity of various ILP models for routing static anycast traffic in SS-FONs over single-mode fiber bundles (SMFBs). The proposed ILP models apply different modeling techniques, i.e., slice-based and lightpath-based. Moreover, proposed models differ with the core switching (lane changes) capability and consideration of DCs location problem. In order to test the complexity and scalability of models, we run simulations assuming a different number of demands, fibers in SMFBs, candidate paths and DCs.