Exploiting the power of multiplicity: a holistic survey of network-layer multipath

The Internet is inherently a multipath network: For an underlying network with only a single path, connecting various nodes would have been debilitatingly fragile. Unfortunately, traditional Internet technologies have been designed around the restrictive assumption of a single working path between a source and a destination. The lack of native multipath support constrains network performance even as the underlying network is richly connected and has redundant multiple paths. Computer networks can exploit the power of multiplicity, through which a diverse collection of paths is resource pooled as a single resource, to unlock the inherent redundancy of the Internet. This opens up a new vista of opportunities, promising increased throughput (through concurrent usage of multiple paths) and increased reliability and fault tolerance (through the use of multiple paths in backup/redundant arrangements). There are many emerging trends in networking that signify that the Internet's future will be multipath, including the use of multipath technology in data center computing; the ready availability of multiple heterogeneous radio interfaces in wireless (such as Wi-Fi and cellular) in wireless devices; ubiquity of mobile devices that are multihomed with heterogeneous access networks; and the development and standardization of multipath transport protocols such as multipath TCP. The aim of this paper is to provide a comprehensive survey of the literature on network-layer multipath solutions. We will present a detailed investigation of two important design issues, namely, the control plane problem of how to compute and select the routes and the data plane problem of how to split the flow on the computed paths. The main contribution of this paper is a systematic articulation of the main design issues in network-layer multipath routing along with a broad-ranging survey of the vast literature on network-layer multipathing. We also highlight open issues and identify directions for future work

Energy management in communication networks: a journey through modelling and optimization glasses

The widespread proliferation of Internet and wireless applications has produced a significant increase of ICT energy footprint. As a response, in the last five years, significant efforts have been undertaken to include energy-awareness into network management. Several green networking frameworks have been proposed by carefully managing the network routing and the power state of network devices. Even though approaches proposed differ based on network technologies and sleep modes of nodes and interfaces, they all aim at tailoring the active network resources to the varying traffic needs in order to minimize energy consumption. From a modeling point of view, this has several commonalities with classical network design and routing problems, even if with different objectives and in a dynamic context. With most researchers focused on addressing the complex and crucial technological aspects of green networking schemes, there has been so far little attention on understanding the modeling similarities and differences of proposed solutions. This paper fills the gap surveying the literature with optimization modeling glasses, following a tutorial approach that guides through the different components of the models with a unified symbolism. A detailed classification of the previous work based on the modeling issues included is also proposed

End-to-End Resilience Mechanisms for Network Transport Protocols

The universal reliance on and hence the need for resilience in network communications has been well established. Current transport protocols are designed to provide fixed mechanisms for error remediation (if any), using techniques such as ARQ, and offer little or no adaptability to underlying network conditions, or to different sets of application requirements. The ubiquitous TCP transport protocol makes too many assumptions about underlying layers to provide resilient end-to-end service in all network scenarios, especially those which include significant heterogeneity. Additionally the properties of reliability, performability, availability, dependability, and survivability are not explicitly addressed in the design, so there is no support for resilience. This dissertation presents considerations which must be taken in designing new resilience mechanisms for future transport protocols to meet service requirements in the face of various attacks and challenges. The primary mechanisms addressed include diverse end-to-end paths, and multi-mode operation for changing network conditions

Development of an Android App to control and manage Cognitive Networks

As the interest in Mobile Ad Hoc networks is constantly growing for tactical, disaster-response situation, academic research and civilian contexts, some new protocol must be implemented to let those network scale. Cognitive networking may solve the problem thanks to its network-wide performances goal. The goal of this project is to develop a working testbed that will be exploited in the study and the analysis of cognitive networking mechanism and algorithms. This tool is developed in Androidope

Cross-layer Assisted TCP Algorithms for Vertical Handoff

The ever expanding growth of the wireless access to the Internet in recent years has led to the proliferation of wireless and mobile devices to connect to the Internet. This has created the possibility of mobile devices equipped with multiple radio interfaces to connect to the Internet using any of several wireless access network technologies such as GPRS, WLAN and WiMAX in order to get the connectivity best suited for the application. These access networks are highly heterogeneous and they vary widely in their characteristics such as bandwidth, propagation delay and geographical coverage. The mechanism by which a mobile device switches between these access networks during an ongoing connection is referred to as vertical handoff and it often results in an abrupt and significant change in the access link characteristics. The most common Internet applications such as Web browsing and e-mail make use of the Transmission Control Protocol (TCP) as their transport protocol and the behaviour of TCP depends on the end-to-end path characteristics such as bandwidth and round-trip time (RTT). As the wireless access link is most likely the bottleneck of a TCP end-to-end path, the abrupt changes in the link characteristics due to a vertical handoff may affect TCP behaviour adversely degrading the performance of the application. The focus of this thesis is to study the effect of a vertical handoff on TCP behaviour and to propose algorithms that improve the handoff behaviour of TCP using cross-layer information about the changes in the access link characteristics. We begin this study by identifying the various problems of TCP due to a vertical handoff based on extensive simulation experiments. We use this study as a basis to develop cross-layer assisted TCP algorithms in handoff scenarios involving GPRS and WLAN access networks. We then extend the scope of the study by developing cross-layer assisted TCP algorithms in a broader context applicable to a wide range of bandwidth and delay changes during a handoff. And finally, the algorithms developed here are shown to be easily extendable to the multiple-TCP flow scenario. We evaluate the proposed algorithms by comparison with standard TCP (TCP SACK) and show that the proposed algorithms are effective in improving TCP behavior in vertical handoff involving a wide range of bandwidth and delay of the access networks. Our algorithms are easy to implement in real systems and they involve modifications to the TCP sender algorithm only. The proposed algorithms are conservative in nature and they do not adversely affect the performance of TCP in the absence of cross-layer information.Käytämme enenevissä määrin kannettavia päätelaitteita (esim. matkapuhelin, kannettava tietokone) erilaisiin sovelluksiin kuten sähköpostin lukemiseen, verkon selaamiseen, musiikin lataamiseen ja kuuntelemiseen, pelien pelaamiseen ja laskujen maksamiseen riippumatta olinpaikastamme tai liikkuvuudestamme. Pystymme yhdistämään laitteemme Internetiin milloin tahansa missä tahansa. Langattomat verkot, jotka mahdollistavat laitteen kytkemisen Internetiin radion kautta käyttävät moninaisia teknologioita ja eroavat laajalti ominaisuuksiltaan. Esimerkiksi langaton lähiverkko (WLAN), jota voidaan käyttää rakennuksen sisällä, on matkapuhelinverkkoa (esim. GPRS) nopeampi verkko, kun taas GPRS-kenttä voi ulottua kokonaisen kaupungin tai maan alueelle ja laajemmallekin. Kannettava päätelaite, jossa on monia radioliittymiä, voi siirtyä käyttämään mitä tahansa monista saatavilla olevistaverkoista riippuen olinpaikasta tai käytettävän sovelluksen tarpeista. Verkonvaihto viittaa tähän verkosta toiseen siirtymiseen, ja se tunnetaan vertikaalisena verkonvaihtona, kun siirtymisen kohteena olevien verkkojen teknologia eroaa toisistaan. TCP on tietoliikenneohjelmisto, jota sekä tiedon lähettäjä että vastaanottaja käyttävät kuljettamaan sovelluksen tiedon luotettavasti. TCP säätelee tiedon lähetysnopeutta riippuen Internetin resurssien saatavuudesta. TCP:n käyttäytyminen riippuu päästä-päähän polun ominaisuuksista ja erityisesti pullonkaulayhteydestä, siitä yhteydestä, jolla on minimikapasiteetti polulla. Langaton yhteys, joka yhdistää kannettavan laitteen Internetiin on usein pullonkaulayhteys, ja äkillinen muutos sen ominaisuuksissa vertikaalisen siirtymän aikana vaikuttaa merkittävästi TCP:n suorituskykyyn ja siten koko sovelluksen laatuun. Tämä työssä on keskitytty tutkimaan TCP:n toimintaa vertikaalisessa verkonvaihdon yhteydessä ja suunnittelemaan algoritmeja, jotka parantavat sen suorituskykyä vertikaalisen verkonvaihdon yhteydessä. Suunnitellut algoritmit käyttävät hyväksi tietoa vertikaaliseen verkonvaihtoon liittyvien langattomien yhteyksien ominaisuuksista. Ensimmäinen tapaustutkimuskohde liittyy WLAN-GPRS -ympäristöön, jossa TCP saa minimimäärän tietoa verkonvaihtoon liittyen. Tulokset näyttävät, että TCP:n suorituskykyä voidaan parantaa huomattavasti. Tutkimusta on laajennettu kattamaan verkonvaihto yleisemmässä tapauksessa käyttäen karkeita arvioita ko. verkkojen ominaisuuksista. Kehitettyjen algoritmien toiminnallisuus on evaluoitu simulaatiokokeilla kattaen laajan joukon ominaisuuksiltaan erilaisia verkkoja. Tulokset osoittavat, että TCP-suorituskykyä voidaan parantaa vertikaalisen verkonvaihdon yhteydessä huomattavasti tätä lähestymistapaa käyttäen. Kehitetyt algoritmit voivat olla hyödyksi etsiessämme ratkaisuja kannettavien laitteiden todellisen käytön tarpeisiin

Minimal deployable endpoint-driven network forwarding: principle, designs and applications

Networked systems now have significant impact on human lives: the Internet, connecting the world globally, is the foundation of our information age, the data centers, running hundreds of thousands of servers, drive the era of cloud computing, and even the Tor project, a networked system providing online anonymity, now serves millions of daily users. Guided by the end-to-end principle, many computer networks have been designed with a simple and flexible core offering general data transfer service, whereas the bulk of the application-level functionalities have been implemented on endpoints that are attached to the edge of the network. Although the end-to-end design principle gives these networked systems tremendous success, a number of new requirements have emerged for computer networks and their running applications, including untrustworthy of endpoints, privacy requirement of endpoints, more demanding applications, the rise of third-party Intermediaries and the asymmetric capability of endpoints and so on. These emerging requirements have created various challenges in different networked systems. To address these challenges, there are no obvious solutions without adding in-network functions to the network core. However, no design principle has ever been proposed for guiding the implementation of in-network functions. In this thesis, We propose the first such principle and apply this principle to propose four designs in three different networked systems to address four separate challenges. We demonstrate through detailed implementation and extensive evaluations that the proposed principle can live in harmony with the end-to-end principle, and a combination of the two principle offers more complete, effective and accurate guides for innovating the modern computer networks and their applications.Ope

Multihoming with ILNP in FreeBSD

Multihoming allows nodes to be multiply connected to the network. It forms the basis of features which can improve network responsiveness and robustness; e.g. load balancing and fail-over, which can be considered as a choice between network locations. However, IP today assumes that IP addresses specify both network location and node identity. Therefore, these features must be implemented at routers. This dissertation considers an alternative based on the multihoming approach of the Identifier Locator Network Protocol (ILNP). ILNP is one of many proposals for a split between network location and node identity. However, unlike other proposals, ILNP removes the use of IP addresses as they are used today. To date, ILNP has not been implemented within an operating system stack. I produce the first implementation of ILNP in FreeBSD, based on a superset of IPv6 – ILNPv6 – and demonstrate a key feature of ILNP: multihoming as a first class function of the operating system, rather than being implemented as a routing function as it is today. To evaluate the multihoming capability, I demonstrate one important application of multihoming – load distribution – at three levels of network hierarchy including individual hosts, a singleton Site Border Router (SBR), and a novel, dynamically instantiated, distributed SBR (dSBR). For each level, I present empirical results from a hardware testbed; metrics include latency, throughput, loss and reordering. I compare performance with unmodified IPv6 and NPTv6. Finally, I evaluate the feasibility of dSBR-ILNPv6 as an alternative to existing multihoming approaches, based on measurements of the dSBR’s responsiveness to changes in site connectivity. We find that multihoming can be implemented by individual hosts and/or SBRs, without requiring additional routing state as is the case today, and without any significant additional load or overhead compared to unicast IPv6

Traffic and task allocation in networks and the cloud

Communication services such as telephony, broadband and TV are increasingly migrating into Internet Protocol(IP) based networks because of the consolidation of telephone and data networks. Meanwhile, the increasingly wide application of Cloud Computing enables the accommodation of tens of thousands of applications from the general public or enterprise users which make use of Cloud services on-demand through IP networks such as the Internet. Real-Time services over IP (RTIP) have also been increasingly significant due to the convergence of network services, and the real-time needs of the Internet of Things (IoT) will strengthen this trend. Such Real-Time applications have strict Quality of Service (QoS) constraints, posing a major challenge for IP networks. The Cognitive Packet Network (CPN) has been designed as a QoS-driven protocol that addresses user-oriented QoS demands by adaptively routing packets based on online sensing and measurement. Thus in this thesis we first describe our design for a novel ``Real-Time (RT) traffic over CPN'' protocol which uses QoS goals that match the needs of voice packet delivery in the presence of other background traffic under varied traffic conditions; we present its experimental evaluation via measurements of key QoS metrics such as packet delay, delay variation (jitter) and packet loss ratio. Pursuing our investigation of packet routing in the Internet, we then propose a novel Big Data and Machine Learning approach for real-time Internet scale Route Optimisation based on Quality-of-Service using an overlay network, and evaluate is performance. Based on the collection of data sampled each $2$ minutes over a large number of source-destinations pairs, we observe that intercontinental Internet Protocol (IP) paths are far from optimal with respect to metrics such as end-to-end round-trip delay. On the other hand, our machine learning based overlay network routing scheme exploits large scale data collected from communicating node pairs to select overlay paths, while it uses IP between neighbouring overlay nodes. We report measurements over a week long experiment with several million data points shows substantially better end-to-end QoS than is observed with pure IP routing. Pursuing the machine learning approach, we then address the challenging problem of dispatching incoming tasks to servers in Cloud systems so as to offer the best QoS and reliable job execution; an experimental system (the Task Allocation Platform) that we have developed is presented and used to compare several task allocation schemes, including a model driven algorithm, a reinforcement learning based scheme, and a ``sensible’’ allocation algorithm that assigns tasks to sub-systems that are observed to provide lower response time. These schemes are compared via measurements both among themselves and against a standard round-robin scheduler, with two architectures (with homogenous and heterogenous hosts having different processing capacities) and the conditions under which the different schemes offer better QoS are discussed. Since Cloud systems include both locally based servers at user premises and remote servers and multiple Clouds that can be reached over the Internet, we also describe a smart distributed system that combines local and remote Cloud facilities, allocating tasks dynamically to the service that offers the best overall QoS, and it includes a routing overlay which minimizes network delay for data transfer between Clouds. Internet-scale experiments that we report exhibit the effectiveness of our approach in adaptively distributing workload across multiple Clouds.Open Acces

Congestion Avoidance Testbed Experiments

DARTnet provides an excellent environment for executing networking experiments. Since the network is private and spans the continental United States, it gives researchers a great opportunity to test network behavior under controlled conditions. However, this opportunity is not available very often, and therefore a support environment for such testing is lacking. To help remedy this situation, part of SRI's effort in this project was devoted to advancing the state of the art in the techniques used for benchmarking network performance. The second objective of SRI's effort in this project was to advance networking technology in the area of traffic control, and to test our ideas on DARTnet, using the tools we developed to improve benchmarking networks. Networks are becoming more common and are being used by more and more people. The applications, such as multimedia conferencing and distributed simulations, are also placing greater demand on the resources the networks provide. Hence, new mechanisms for traffic control must be created to enable their networks to serve the needs of their users. SRI's objective, therefore, was to investigate a new queueing and scheduling approach that will help to meet the needs of a large, diverse user population in a "fair" way