Robust geometric forest routing with tunable load balancing

Although geometric routing is proposed as a memory-efficient alternative to traditional lookup-based routing and forwarding algorithms, it still lacks: i) adequate mechanisms to trade stretch against load balancing, and ii) robustness to cope with network topology change. The main contribution of this paper involves the proposal of a family of routing schemes, called Forest Routing. These are based on the principles of geometric routing, adding flexibility in its load balancing characteristics. This is achieved by using an aggregation of greedy embeddings along with a configurable distance function. Incorporating link load information in the forwarding layer enables load balancing behavior while still attaining low path stretch. In addition, the proposed schemes are validated regarding their resilience towards network failures

Message and time efficient multi-broadcast schemes

We consider message and time efficient broadcasting and multi-broadcasting in wireless ad-hoc networks, where a subset of nodes, each with a unique rumor, wish to broadcast their rumors to all destinations while minimizing the total number of transmissions and total time until all rumors arrive to their destination. Under centralized settings, we introduce a novel approximation algorithm that provides almost optimal results with respect to the number of transmissions and total time, separately. Later on, we show how to efficiently implement this algorithm under distributed settings, where the nodes have only local information about their surroundings. In addition, we show multiple approximation techniques based on the network collision detection capabilities and explain how to calibrate the algorithms' parameters to produce optimal results for time and messages.Comment: In Proceedings FOMC 2013, arXiv:1310.459

Scalable Routing Easy as PIE: a Practical Isometric Embedding Protocol (Technical Report)

We present PIE, a scalable routing scheme that achieves 100% packet delivery and low path stretch. It is easy to implement in a distributed fashion and works well when costs are associated to links. Scalability is achieved by using virtual coordinates in a space of concise dimensionality, which enables greedy routing based only on local knowledge. PIE is a general routing scheme, meaning that it works on any graph. We focus however on the Internet, where routing scalability is an urgent concern. We show analytically and by using simulation that the scheme scales extremely well on Internet-like graphs. In addition, its geometric nature allows it to react efficiently to topological changes or failures by finding new paths in the network at no cost, yielding better delivery ratios than standard algorithms. The proposed routing scheme needs an amount of memory polylogarithmic in the size of the network and requires only local communication between the nodes. Although each node constructs its coordinates and routes packets locally, the path stretch remains extremely low, even lower than for centralized or less scalable state-of-the-art algorithms: PIE always finds short paths and often enough finds the shortest paths.Comment: This work has been previously published in IEEE ICNP'11. The present document contains an additional optional mechanism, presented in Section III-D, to further improve performance by using route asymmetry. It also contains new simulation result

Efficient Topology Management and Geographic Routing in High-Capacity Continental-Scale Airborne Networks

Large-scale high-capacity communication networks among mobile airborne platforms are quickly becoming a reality. Today, both Google and Facebook are seeking to form networks among high-flying balloons and drones in an effort to provide Internet connections from the stratosphere to users on the ground. This dissertation proposes an alternative, namely using the cargo and passenger aircraft already in the skies as the principal components of such a network. My work presents the design of a network architecture to overcome the challenges of managing the topology of and routing data within these continental-scale highly-dynamic networks. The architecture relies on directional communication links, such as free-space optical communication links (FSO), to achieve high data rates over long distances. However, these state-of-the-art communication systems present new networking challenges. One such challenge is that of managing the physical topology of the network. Such a topology must be explicitly managed, ensuring that each directional data link is pointed at and connected with an appropriate neighbor (which is also pointing back) to yield an acceptable global topology. To overcome this challenge, a distributed topology management framework and associated topology generation algorithms were designed, implemented, and tested via simulation. The framework is capable of managing the topology of thousands of nodes in a continental-scale airborne network and has no communication overhead except that required to exchange position information among nearby nodes. A second component of the work concerns routing data at high data rates through a constantly changing network topology. To address this issue Topology Aware Geographic Routing (TAG), a position-based routing protocol was developed that strategically uses local topology information to make better local forwarding decisions, decreasing the number of hops required to deliver a packet, when compared with other geographic routing protocols. In addition, unlike other similar protocols, TAG is able to reliably deliver packets even when the topology changes while the packet is in flight. These protocols are tested and validated in a series of simulations where nodes trace the trajectories recorded from thousands of actual flights. These simulations indicate that the topology management framework and TAG are able to perform well in large-scale high-density conditions, over long durations, and are able to support tens of thousands of 1 Mbps flows.Doctor of Philosoph

Enabling DTN-based web access : the server side

Verkkoympäristö, jossa modernit protokollat joutuvat toimimaan ei ole enää vain staattinen ja yhtenäinen Internet. Verkkopalvelujen kysynnän kasvaessa Internet levittäytyy entistä monimuotoisempiin ympäristöihin, kuten mobiileihin ad-hoc-verkkoihin. Näissä ympäristöissä toimivat verkot eivät välttämättä täytä tiettyjä ehtoja, jotka ovat edellytyksenä nykyisten Internet-protokollien käytölle. Tällöin näiden protokollien käyttö voi olla vaikeaa tai jopa mahdotonta. Delay-tolerant Networking (DTN) on eräs lähestymistapa, jolla voidaan ratkaista haastavien verkkoympäristöjen aiheuttamia ongelmia. Tämän diplomityön ensimmäinen tavoite on mahdollistaa WWW:n käyttö DTN-verkoissa. Käytännössä tämä tarkoittaa HTTP-protokollan sovittamista DTN:n kuljetuskerrosprotokollan ("bundle protocol") päälle. DTN-ympäristössä yhteydet voivat olla katkonaisia ja tiedonsiirtoviiveet pitkiä, minkä vuoksi on tärkeää välttää turhaa edestakaista viestiliikennettä kommunikoivien noodien välillä. Normaalisti HTTP toimii siten, että se hakee WWW-sivuun liittyvät resurssit yksitellen. Tämä aiheuttaa turhaa liikennettä, joten HTTP ei suoraan sovellu DTN-ympäristöön. Työssä määritellään käsite "resource bundling", jonka avulla HTTP voidaan sovittaa paremmin DTN-yhteensopivaksi. Perusidea on koota WWW-sivun resurssit yhteen pakettiin, jolloin sivun noutamiseen tarvittavien edestakaisten protokollaviestien määrä saadaan minimoitua. Työn toinen tavoite on toteuttaa WWW-palvelinohjelma, joka tukee työssä määriteltyä "resource bundling"-konseptia. Palvelin pohjautuu kahteen vapaan lähdekoodin ohjelmakomponenttiin, jotka ovat vastuussa alemman tason protokollaoperaatioista sekä HTTP-palvelimen perustoiminnoista. Integroimalla nämä komponentit ja kehittämällä resurssien käsittelyyn liittyvä korkeamman tason logiikka, työssä toteutetaan natiivi DTN-pohjainen WWW-palvelin. Työssä myös suoritetaan mittauksia, joilla varmistetaan palvelimen soveltuvuus sen todelliseen käyttöympäristöön ja lisäksi todetaan, että suunniteltu järjestelmä todella parantaa WWW:n käyttömahdollisuuksia haastavissa verkko-olosuhteissa.The networking landscape in which modern protocols must operate is no longer just the static, homogeneous Internet. As the demand for ubiquitous connectivity grows, the Internet stretches out to increasingly diverse environments, such as mobile ad-hoc networks. In these environments, certain assumptions that current Internet protocols rely on may not hold, thus making these protocols inefficient or even useless. Delay-tolerant Networking (DTN) is one approach to solving the problems that arise in such settings. In this thesis, our first objective is to conceptualize the mechanisms needed to enable web access in a DTN environment. More specifically, the goal is to run the Hypertext Transfer Protocol (HTTP) on top of the DTN transport protocol (i.e., the bundle protocol). In a DTN environment, where connectivity may be intermittent and transmission delays long, it is important to avoid unnecessary round-trips between the communicating nodes. Consequently, HTTP is not directly applicable to DTN due to its conversational style of operation in which the resources of a web page are fetched one at a time. We adapt HTTP to the DTN environment by introducing the concept of resource bundling, which means that web resources are grouped together into larger aggregates in order to minimize the number of round-trips required to retrieve a web page. The second objective of the thesis is to implement the resource bundling concept in a web server application. The server builds on two major open source software components that handle the low-level bundle protocol operations and form the basis of the HTTP server logic. We integrate these pieces and extend them with the high-level resource bundling logic to produce a native DTN web server. We also perform measurements on the server, verifying its adeptness for real-world deployment and proving that the resource bundling concept truly has a positive impact on the web browsing experience in challenged network environments

Computing infrastructure issues in distributed communications systems : a survey of operating system transport system architectures

The performance of distributed applications (such as file transfer, remote login, tele-conferencing, full-motion video, and scientific visualization) is influenced by several factors that interact in complex ways. In particular, application performance is significantly affected both by communication infrastructure factors and computing infrastructure factors. Several communication infrastructure factors include channel speed, bit-error rate, and congestion at intermediate switching nodes. Computing infrastructure factors include (among other things) both protocol processing activities (such as connection management, flow control, error detection, and retransmission) and general operating system factors (such as memory latency, CPU speed, interrupt and context switching overhead, process architecture, and message buffering). Due to a several orders of magnitude increase in network channel speed and an increase in application diversity, performance bottlenecks are shifting from the network factors to the transport system factors.This paper defines an abstraction called an "Operating System Transport System Architecture" (OSTSA) that is used to classify the major components and services in the computing infrastructure. End-to-end network protocols such as TCP, TP4, VMTP, XTP, and Delta-t typically run on general-purpose computers, where they utilize various operating system resources such as processors, virtual memory, and network controllers. The OSTSA provides services that integrate these resources to support distributed applications running on local and wide area networks.A taxonomy is presented to evaluate OSTSAs in terms of their support for protocol processing activities. We use this taxonomy to compare and contrast five general-purpose commercial and experimental operating systems including System V UNIX, BSD UNIX, the x-kernel, Choices, and Xinu

GPU Accelerated protocol analysis for large and long-term traffic traces

This thesis describes the design and implementation of GPF+, a complete general packet classification system developed using Nvidia CUDA for Compute Capability 3.5+ GPUs. This system was developed with the aim of accelerating the analysis of arbitrary network protocols within network traffic traces using inexpensive, massively parallel commodity hardware. GPF+ and its supporting components are specifically intended to support the processing of large, long-term network packet traces such as those produced by network telescopes, which are currently difficult and time consuming to analyse. The GPF+ classifier is based on prior research in the field, which produced a prototype classifier called GPF, targeted at Compute Capability 1.3 GPUs. GPF+ greatly extends the GPF model, improving runtime flexibility and scalability, whilst maintaining high execution efficiency. GPF+ incorporates a compact, lightweight registerbased state machine that supports massively-parallel, multi-match filter predicate evaluation, as well as efficient arbitrary field extraction. GPF+ tracks packet composition during execution, and adjusts processing at runtime to avoid redundant memory transactions and unnecessary computation through warp-voting. GPF+ additionally incorporates a 128-bit in-thread cache, accelerated through register shuffling, to accelerate access to packet data in slow GPU global memory. GPF+ uses a high-level DSL to simplify protocol and filter creation, whilst better facilitating protocol reuse. The system is supported by a pipeline of multi-threaded high-performance host components, which communicate asynchronously through 0MQ messaging middleware to buffer, index, and dispatch packet data on the host system. The system was evaluated using high-end Kepler (Nvidia GTX Titan) and entry level Maxwell (Nvidia GTX 750) GPUs. The results of this evaluation showed high system performance, limited only by device side IO (600MBps) in all tests. GPF+ maintained high occupancy and device utilisation in all tests, without significant serialisation, and showed improved scaling to more complex filter sets. Results were used to visualise captures of up to 160 GB in seconds, and to extract and pre-filter captures small enough to be easily analysed in applications such as Wireshark