Nos últimos anos, houve um aumento da complexidade e variedade de serviços disponíveis na Internet, fato que tem levado à busca por técnicas eficientes de roteamento de requisições de um cliente ao melhor servidor disponível, sendo uma delas conhecida como application layer anycast (ALA). O objetivo deste mestrado é elaborar meios eficientes de prover anycast na camada de aplicação com qualidade de serviço no contexto de computação em nuvem. Para atingir esse objetivo, um novo sistema foi proposto (GALA, Global Application Layer Anycast). Ele herda características de um outro sistema existente e emprega a geolocalização como diferencial, a fim de melhorar o desempenho geral do algoritmo. Experimentos foram realizados por meio de simulação e os resultados mostraram que esse novo sistema, comparado ao algoritmo herdado, mantém a eficiência das requisições realizadas pelos clientes e diminui consideravelmente o tempo de latência dessas operações. Ainda, o sistema proposto foi desenvolvido em um ambiente real a fim de fortalecer os resultados das simulações. Com os resultados obtidos, o sistema modelado foi validado e sua eficácia confirmada. / In the past years, the complexity and variety of available services expanded in the Internet, fact that is drawing attention of many researchers that wish to find out efficient techniques of routing client requests to the closest server, being one of them known as application layer anycast (ALA). Thus, the objective of this research is to elaborate ways to offer application layer anycast that are scalable and select the closest servers with the shortest latency possible, in the context of cloud computing. To achieve this goal, a new system was proposed (GALA, Global Application Layer Anycast). It inherits features from an existing system and applies geolocation to improve its overall performance. Simulation results indicated that the new system, compared to its antecessor, has the same efficiency but decreases considerably the requests latency. Yet, the proposed system was deployed in a real environment to strengthen the simulations results. With the obtained data, the modeled system was validated and its efficiency confirmed.

A new approach to distributed network simulations that eases the burdens on the simulation developer in creating space-parallel simulations is presented. It provides a full-topology knowledge for every federate (simulator instance) to make the best routing decision to destinations simulated at other federates. Later, this technique was used to characterize the benefits of IP Anycast mechanism at large scale. Different IP Anycast scenarios were simulated in a detailed Border Gateway Protocol (BGP) simulator using a realistic large-scale AS topology. Results indicated that Anycast indeed provides higher availability and decreased end-to-end delay. It also showed that Anycast does not provide load balancing, and the BGP overhead associated with a topology change is reduced when Anycast is deployed. In addition, a simulation model of Enhanced Interior Gateway Routing Protocol (EIGRP) was developed and used to present a new approach for host mobility within an AS. The new solution is to allow end systems to retain a fixed IP address as those systems move across subnet boundaries, and to use route advertisement updates (by EIGRP) to inform routers of new or revised routes to reach the mobile hosts as they migrate. The simulation results showed the viability of this approach, and the ability of EIGRP to update routing tables in a timely fashion.

Nos últimos anos, houve um aumento da complexidade e variedade de serviços disponíveis na Internet, fato que tem levado à busca por técnicas eficientes de roteamento de requisições de um cliente ao melhor servidor disponível, sendo uma delas conhecida como application layer anycast (ALA). O objetivo deste mestrado é elaborar meios eficientes de prover anycast na camada de aplicação com qualidade de serviço no contexto de computação em nuvem. Para atingir esse objetivo, um novo sistema foi proposto (GALA, Global Application Layer Anycast). Ele herda características de um outro sistema existente e emprega a geolocalização como diferencial, a fim de melhorar o desempenho geral do algoritmo. Experimentos foram realizados por meio de simulação e os resultados mostraram que esse novo sistema, comparado ao algoritmo herdado, mantém a eficiência das requisições realizadas pelos clientes e diminui consideravelmente o tempo de latência dessas operações. Ainda, o sistema proposto foi desenvolvido em um ambiente real a fim de fortalecer os resultados das simulações. Com os resultados obtidos, o sistema modelado foi validado e sua eficácia confirmada. / In the past years, the complexity and variety of available services expanded in the Internet, fact that is drawing attention of many researchers that wish to find out efficient techniques of routing client requests to the closest server, being one of them known as application layer anycast (ALA). Thus, the objective of this research is to elaborate ways to offer application layer anycast that are scalable and select the closest servers with the shortest latency possible, in the context of cloud computing. To achieve this goal, a new system was proposed (GALA, Global Application Layer Anycast). It inherits features from an existing system and applies geolocation to improve its overall performance. Simulation results indicated that the new system, compared to its antecessor, has the same efficiency but decreases considerably the requests latency. Yet, the proposed system was deployed in a real environment to strengthen the simulations results. With the obtained data, the modeled system was validated and its efficiency confirmed.

In response to the presence of portable devices and the change in usage patterns, mobility support for computer networking has received increasing attentions in recent years. There has been wide variety of established works focusing on the shortening of the handover delay. Most of them had tried their best in maintaining the connections to their peer nodes as mobile nodes moving across different network domains. This might not be a best policy in certain applications, such as homogeneous content distribution systems. A new handover scheme incorporating anycasting and service migration is developed and presented in this thesis. In the proposed approach, anycast is used to locate a new nearest server as a mobile node entering a new domain, and an ongoing service will be dynamically migrated from a distant server to a new server with shorter weighted network distance to the client. As a result, the individual service connection, as well as the global network environment, will benefit from the service migration, in terms of improved service quality and bandwidth utilization.

Anycast is a new communication service defined in IPv6 (Internet Protocol Version 6) [6]. An anycast message is the one that should be delivered to the 'nearest' member in a group of designated recipients. The ¡¥nearest¡¦ is not always the ¡¥best¡¦ member. In this paper, we propose a routing protocol for anycast message. It is composed of two subprotocols: the routing table establishment subprotocol and the packet forwarding subprotocol. In the routing table establishment subprotocol, we propose a mininum delay path method (MDP). We get a minimum delay path from router to destination by MDP. In the packet forwarding protocol, we propose a minimum delay and load balancing method (MDLB). We dispatch traffic load to a server with minimum delay and light load by MDLB. The performance has demonstrated the benefits of MDP and MDLB in reducing end-to-end delay and increasing throughput of network.

When a service on the internet is scaled horizontally with multiple server instances, there are different solutions on how to map a client request to one of those server instances. In this paper I am evaluating a select few solutions for using the nearest server instance to handle a client request. I classified those solutions on the criteria ease of use, does this solution require a change of program behavior, how many resources are required for set up, the response time, are there already existing open source software or open data solutions available, how accurate is the solution, does it scale horizontally and lastly how robust the solution is. In this paper I evaluated GeoDNS, a central hyper text transfer protocol (HTTP) redirect server, decentralized instances and using an Anycast internet protocol (IP) address as a solution. Based on the described evaluation criteria I found that the central redirect server in combination with a GeoDNS server works best to map a client request to the nearest server instance. The decentralized instances are a specialization of the redirect server and setting up a public routable Anycast address is complicated. I compared three methods of matching a client IP address to a geolocation. In this practical implementation I found using local files matching IP ranges to countries works best over using regional internet registry provided registration data access protocol (RDAP) endpoints or using the same RDAP method with a cache. The local mapping file implementation is the fastest, compared to the other described implementation, and less error-prone. The entire source code of this work and implemented programs can be found here (https://paulgo.dev/mrpaulblack/bachelor-thesis).:1 Introduction and Intention 2 Solutions 2.1 Geolocation DNS 2.2 Central Redirect Server 2.3 Decentralized Implementation 2.4 IP Anycast 3 Implementation 3.1 Experiment Setup 3.2 Method of Observation 3.3 Observations and Analysis 4 Conclusion Bibliography List of Figures List of Tables List of Source Codes

In this thesis, the impact of multihomed clients and multihomed proxy servers on the performance of modern networks is investigated. The network model used in our investigation integrates three main components: the new one-to-any Anycast communication paradigm that facilitates server replication, the next generation Internet Protocol Version 6 (IPv6) that offers larger address space for packet switched networks, and the emerging multihoming trend of connecting devices and smart phones to more than one Internet service provider thereby acquiring more than one IP address. The design of a previously proposed Proxy IP Anycast service is modified to integrate user device multihoming and Ipv6 routing. The impact of user device multihoming (single-homed, dual-homed, and triple-homed) on network performance is extensively analyzed using realistic network topologies and different traffic scenarios of client-server TCP flows. Network throughput, packet latency delay and packet loss rate are the three performance metrics used in our analysis. Performance comparisons between the Anycast Proxy service and the native IP Anycast protocol are presented. The number of Anycast proxy servers and their placement are studied. Five placement methods have been implemented and evaluated including random placement, highest traffic placement, highest number of active interface placements, K-DS placement and a new hybrid placement method. The work presented in this thesis provides new insight into the performance of some new emerging communication paradigms and how to improve their design. Although the work has been limited to investigating Anycast proxy servers, the results can be beneficial and applicable to other types of overlay proxy services such as multicast proxies.

There are two critical issues involved as a mobile node moving across two different network sub-domains. One of them is to minimize the possible packet loss and the other is to shorten the handover time. Fast handover is a remedy to these problems. It minimizes the packet loss by making use of buffers, and speed up the handover procedure by L2 triggering. There are two components contributing to the handover delay, namely L2 handover delay and L3 handover delay. The L3 handover delay consists of movement detection delay, duplicate address detection delay, as well as registration delay. With fast handover, the movement detection delay can be lowered by using L2 trigger, and the registration delay can be decreased by buffering and tunneling. However, the problem of out-of-order packets is still in its existence. A novel handover scheme incorporating the anycast technology is developed and presented in this thesis. With refined buffer control scheme and the switching between unicast and anycast addressing, the handover performance can be greatly improved by the proposed approach.

With increased popularity and pervasiveness, mobile networking had become a definite trend for future networks. Users strongly demand the retaining of the connectivity and the QoS (Quality of Service) of ongoing services while roaming across different points of attachment. Efficient handover schemes and service paradigms are essential to the above vision. We will contribute to the QoS provisioning in mobile wireless networks from two complementary perspectives: one is the improved handover schemes at the client end for shorter latency and less packet loss, and the other is the service migration at server end for improved QoS. There are time-consuming procedures involved in the handover process. Various research works had devoted to the acceleration of movement detection and registration. However, a time-consuming operation, duplicate address detection, was overlooked by most studies. A novel scheme featuring anycast / multicast technique is developed and presented in this dissertation. The proposed approach switches to anycast / multicast addressing during handover and switches back to normal unicast addressing after all required operations are completed. By switching to anycast / multicast addressing, a mobile node can continue the reception of packets from its corresponding node before its new care-of address is actually validated. As a result, transmission disruption can be effectively minimized. In addition, simple but effective buffer control schemes are designed to reduce possible packet loss and to prevent the out-of-order problem. Analytical study reveals that improved performance can be guaranteed, as reflected in the simulation results. The establishment of mobility-supported Internet protocols, such as IPv4 and IPv6, had made it possible that an ongoing service can be retained while a mobile node is roaming across different access domains. However, limited efforts had been paid to server sides if we consider the topological change due to node mobility. In the global network environment, the weighted network distance between a client and its server could change dramatically for reasons of topology change or node mobility. A new network service framework highlighting the concept of service migration is presented in this dissertation. The proposed framework take into account essential service quality factors, such as server loading, bandwidth, delay, and so on, and then dynamically migrates an ongoing service from a distant server to a new server with shorter ¡§weighted network distance¡¨ to the client. As a result, the individual service connection, as well as the global network environment, will benefit from the service migration, in terms of improved service quality and bandwidth utilization. This dissertation explains the general architecture of the proposed framework and focuses on the technical details of the core component - service migration module. Our experiences on the functional prototypes for service migration are also reported. The success of the prototyping system is an indication of the feasibility and effectiveness of the proposed scheme.

Tato diplomová práce se zabývá metodami pro výběr nejbližší RTP proxy k VoIP klientům s použitím IP anycastu. RTP proxy servery jsou umístěny v síti Internetu a přeposílají RTP data pro VoIP klienty za síťovými překladači adres(NAT). Bez zeměpisně rozmístěných RTP proxy serverů a metod pro nalezení nejbližšího RTP proxy serveru by došlo ke zbytečnému poklesu kvality přenosu médialních dat a velkému zpoždení. Tento dokument navrhuje 4 metody a jejich porovnání s podrobnějšími rozbory metod s využitím DNS resolvování a přímo SIP protokolu. Tento dokument také obsahuje měření chování IP anycastu v porovnání mezi metrikami směrování a metrikami časovými. Nakonec dokumentu je také uvedena implemetace na SIP Express Router platformě.