There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Applied Probability and Queues.

Space-air-ground integrated network (SAGIN), as an integration of satellite systems, aerial networks, and terrestrial communications, has been becoming an emerging architecture and attracted intensive research interest during the past years. Besides bringing significant benefits for various practical services and applications, SAGIN is also facing many unprecedented challenges due to its specific characteristics, such as heterogeneity, self-organization, and time-variability. Compared to traditional ground or satellite networks, SAGIN is affected by the limited and unbalanced network resources in all three network segments, so that it is difficult to obtain the best performances for traffic delivery. Therefore, the system integration, protocol optimization, resource management, and allocation in SAGIN is of great significance. To the best of our knowledge, we are the first to present the state-of-the-art of the SAGIN since existing survey papers focused on either only one single network segment in space or air, or the integration of space-ground, neglecting the integration of all the three network segments. In light of this, we present in this paper a comprehensive review of recent research works concerning SAGIN from network design and resource allocation to performance analysis and optimization. After discussing several existing network architectures, we also point out some technology challenges and future directions.

Space-Air-Ground Integrated Network: A Survey

Information-Centric Networking (ICN) is a novel networking paradigm that attracts increasing research interests in recent years In-network caching has been viewed as an attractive feature of ICN because it can reduce network traffic, alleviate server bottleneck, and reduce the user access latencies Because of this, the network community has proposed many in-network caching mechanisms that aim at optimizing various performance metrics such as cache hit ratio and cache hit distance In this survey, we present a comprehensive overview of the recently proposed in-network caching mechanisms for ICN For each caching mechanism, we describe it in detail, present examples to illustrate how it works, and analyze its possible benefits and drawbacks We also compare some typical in-network caching mechanisms through extensive simulations and discuss the remaining research challenges

A Survey of Caching Mechanisms in Information-Centric Networking

The Host Identity Protocol (HIP) is an inter-networking architecture and an associated set of protocols, developed at the IETF since 1999 and reaching their first stable version in 2007. HIP enhances the original Internet architecture by adding a name space used between the IP layer and the transport protocols. This new name space consists of cryptographic identifiers, thereby implementing the so-called identifier/locator split. In the new architecture, the new identifiers are used in naming application level end-points (sockets), replacing the prior identification role of IP addresses in applications, sockets, TCP connections, and UDP-based send and receive system calls. IPv4 and IPv6 addresses are still used, but only as names for topological locations in the network. HIP can be deployed such that no changes are needed in applications or routers. Almost all pre-compiled legacy applications continue to work, without modifications, for communicating with both HIP-enabled and non-HIP-enabled peer hosts. The architectural enhancement implemented by HIP has profound consequences. A number of the previously hard networking problems become suddenly much easier. Mobility, multi-homing, and baseline end-to-end security integrate neatly into the new architecture. The use of cryptographic identifiers allows enhanced accountability, thereby providing a base for easier build up of trust. With privacy enhancements, HIP allows good location anonymity, assuring strong identity only towards relevant trusted parties. Finally, the HIP protocols have been carefully designed to take middle boxes into account, providing for overlay networks and enterprise deployment concerns. This article provides an in-depth look at HIP, discussing its architecture, design, benefits, potential drawbacks, and ongoing work.

/pdf/host-identity-protocol-hip-connectivity-mobility-multi-s66rofb9zb.pdf

Host Identity Protocol (HIP): Connectivity, Mobility, Multi-Homing, Security, and Privacy over IPv4 and IPv6 Networks

Smart devices equipped with multiple network interfaces are becoming commonplace. Nevertheless, even though multiple interfaces can be used to connect to the Internet, their capabilities have not been fully utilized yet because the default TCP/IP stack supports only a single interface for communication. This situation is now changing due to the emergence of multipath protocols on different network stack layers. For example, many IP level approaches have been proposed utilizing tunneling mechanisms for hiding multipath transmission from the transport protocols. Several working groups under IEEE and IETF are actively standardizing multipath transmission on the link layer and transport layer. Application level approaches enable multipath transmission capability by establishing multiple transport connections and distributing data over them. Given all these efforts, it is beneficial and timely to summarize the state-of-the-art, compare their pros and cons, and discuss about the future directions. To that end, we present a survey on multipath transmission and make several major contributions: 1) we present a complete taxonomy pertaining to multipath transmission, including link, network, transport, application, and cross layers; 2) we survey the state-of-the-art for each layer, investigate the problems that each layer aims to address, and make comprehensive assessment of the solutions; and 3) based on the comparison, we identify open issues and pinpoint future directions for multipath transmission research.

/pdf/multipath-transmission-for-the-internet-a-survey-3nw9pidqx7.pdf

Multipath Transmission for the Internet: A Survey

Information-centric network (ICN), which is one of the prominent Internet re-design architectures, relies on in-network caching for its fundamental operation. However, previous works argue that the performance of in-network caching is highly degraded with the current cache-along-default-path design, which makes popular objects to be cached redundantly in many places. Thus, it would be beneficial to have a distributed and uncoordinated design. Although cooperative caches could be an answer to this, previous research showed that they are generally unfeasible due to excessive signaling burden, protocol complexity, and a need for fault tolerance. In this work we illustrate the ICN caching problem, and propose a novel architecture to overcome the problem of uncooperative caches. Our design possesses the cooperation property intrinsically. We utilize controlled off-path caching to achieve almost 9-fold increase in cache efficiency, and around 20% increase in server load reduction when compared to the classic on-path caching used in ICN proposals.

Cooperative caching through routing control in information-centric networks

Multipath TCP (MPTCP) suffers from the degradation of goodput in the presence of diverse network conditions on the available subflows. The goodput can even be worse than that of one regular TCP, undermining the advantage gained by using multipath transfer. In this work, we propose a new multipath TCP protocol, namely NC-MPTCP, which introduces network coding (NC) to some but not all subflows traveling from source to destination. At the core of our scheme is the mixed use of regular and NC subflows. Thus, the regular subflows deliver original data while the NC subflows deliver linear combinations of the original data. The idea is to take advantage of the redundant NC data to compensate for the lost or delayed data in order to avoid receive buffer becoming full. We design a packet scheduling algorithm and a redundancy estimation algorithm to allocate data among different subflows in order to optimize the overall goodput. We also give a guideline on how to choose the NC subflows among the available subflows. We evaluate the performance of NC-MPTCP through a NS-3 network simulator. The experiments show that NC-MPTCP achieves higher goodput compared to MPTCP in the presence of different subflow qualities. And in the worst case, the performance of NC-MPTCP is close to that of one regular TCP.

Network coding based multipath TCP

Public cloud platforms might start with homogeneous hardware; nevertheless, because of inevitable hardware upgrades, or adding more capacity, the initial homogeneous platform will gradually evolve into heterogeneous as time passes by. The consequent performance heterogeneity is of concern to cloud users. In this paper, we evaluate performance variations from hardware heterogeneity and scheduling mechanisms of public clouds. Amazon Elastic Compute Cloud (Amazon EC2) and Rackspace Cloud are used as the representatives because of their relatively long record and wide usage among small and medium enterprises (SMEs). A comprehensive set of microbenchmarks and application-level macrobenchmarks have been used to investigate performance variation. Several major contributions have been made. First, we find out that heterogeneous hardware is a commonality among the relatively long-lasting cloud platforms, although the level of heterogeneity varies. Second, we observe that heterogeneous hardware is the primary culprit of performance variation of cloud platforms. Third, we discover that varied CPU acquisition percentages and different virtual machine scheduling mechanisms exacerbate the performance variation problem, especially for network related operations. Finally, based on the observations, we propose cost-saving approaches and analyze Nash equilibrium from cloud user perspective. By using a simple "trial-and-better" approach, i.e., keep good-performing instances and discard bad-performing instances, cloud users can achieve up to 30 percent cost saving.

Is the Same Instance Type Created Equal? Exploiting Heterogeneity of Public Clouds

https://cs.helsinki.fi/u/gurtov/papers/hi3_report.pdf

Andrey Lukyanenko

Papers

Multipath Transmission for the Internet: A Survey

Cooperative caching through routing control in information-centric networks

Network coding based multipath TCP

Is the Same Instance Type Created Equal? Exploiting Heterogeneity of Public Clouds

Hi3: An efficient and secure networking architecture for mobile hosts