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

A comprehensive open package format for preservation and distribution of geospatial data and metadata

The complexities of the intricate geospatial resources and formats make preservation and distribution of GIS data difficult even among experts. The proliferation of, for instance, KML, Internet map services, etc, reflects the need for sharing geodata but a comprehensive solution when having to deal with data and metadata of a certain complexity is not currently provided. Original geospatial data is usually divided into several parts to record its different aspects (spatial and thematic features, etc), plus additional files containing, metadata, symbolization specifications and tables, etc; these parts are encoded in different formats, both standard and proprietary. To simplify data access, software providers encourage the use of an additional element that we call generically "map project", and this contains links to other parts (local or remote). Consequently, in order to distribute the data and metadata refereed by the map in a complete way, or to apply the Open Archival Information System (OAIS) standard to preserve it for the future, we need to face the multipart problem. This paper proposes a package allowing the distribution of real (comprehensive although diverse and complex) GIS data over the Internet and for data preservation. This proposal, complemented with the right tools, hides but keeps the multipart structure, so providing a simpler but professional user experience. Several packaging strategies are reviewed in the paper, and a solution based on ISO 29500-2 standard is chosen. The solution also considers the adoption of the recent Open Geospatial Consortium Web Services common standard (OGC OWS) context document as map part, and as a way for also combining data files with geospatial services. Finally, and by using adequate strategies, different GIS implementations can use several parts of the package and ignore the rest: a philosophy that has proven useful (e.g. in TIFF)

Web browser for delay-tolerant networks

Due to growth of the Internet, the number of devices increasing and the structure of networks becoming more complex, the problem of time delays during information transmissions has arisen. In environments with long transmission delays modern protocols may become inefficient or even useless. Delay-tolerant Networking (DTN) is one approach that allows to solve the problem of long transmission delay times. In the thesis, an approach to web access in such networks is proposed. The problem of data transmission in the networks with long delays is considered. Special methods exist for data transmission in computer networks. But traditional data transmission protocols do not work well in networks with long delays, e.g. when transmitting over long distances, such as in space, or when connectivity may be disrupted, such as in mobile networks. It is necessary, therefore, to replace TCP and to change the existing web protocol (Hypertext Transfer Protocol - HTTP) in order to allow HTTP data transmissions in DTN environments. In the thesis, HTTP is analyzed and an adaptation of HTTP to DTN environments, as proposed in earlier research, is reviewed and extended further. A client part is created and the implementation is described. The client allows solving the problem of HTTP over DTN usage. An open-source browser is modified and the necessary extensions are developed. The extensions allow to use the DTN transport protocol (i.e. the Bundle Protocol) as another option of transport other than TCP. The software module for a web browser is built on the Mozilla platform. It was shown that it is possible to create a browser to work in DTNs

Web Traffic Data Export to MAFF

Cílem této bakalářské práce bylo seznámení se s principy přenosu, uložení a opětovného zobrazení webového provozu. Další částí byl návrh a realizace modulu pro rekonstrukci a exportování obsahu webového provozu. Tento modul umožňuje poskládat webové stránky získané ze zachycené webové komunikace. Rovněž umožňuje takové stránky zobrazit. Výstupy modulu jsou tvořeny pomocí archivačního formátu MAFF, který slouží k uložení webové stránky pro možnost pozdějšího zobrazení. Základní ověření funkčnosti modulu probíhalo pomocí sad testů.The goal of this bachelor thesis was to get acquainted with the principles of transmission, storage and re-visualisation of web traffic. The next part lied with the design and realization of the module for the reconstruction and exporting of the web traffic contents. This module allows to assemble the websites acquired from the captured web communication. It also allows to visualize such websites. The outputs of the module are made through the archival format MAAF, which serves to store web pages for the option of later display. The basic validation of the module functionality was done using test sets.

Auto smart text and e-mail notification system (ASTENS)

The purpose of Auto Smart Text and E-mail Notification System (ASTENS) project is to provide the California State University San Bernardino and other universities with a new easy, fast, and convenient way of communication between the faculty members and their students. ASTENS (Auto Smart Text and E-mail Notification System) provides two types of communication: class notifications and grade notifications. First, the class notifications allow an instructor to communicate with students registered in his/her class by using his/her cell phone or email. These notifications could be any message related to class (e.g. notes, reminder, announcement, etc.) and every student will be notified via text message and email

Data availability in challenging networking environments in presence of failures

This Doctoral thesis presents research on improving data availability in challenging networking environments where failures frequently occur. The thesis discusses the data retrieval and transfer mechanisms in challenging networks such as the Grid and the delay-tolerant networking (DTN). The Grid concept has gained adaptation as a solution to high-performance computing challenges that are faced in international research collaborations. Challenging networking is a novel research area in communications. The first part of the thesis introduces the challenges of data availability in environment where resources are scarce. The focus is especially on the challenges faced in the Grid and in the challenging networking scenarios. A literature overview is given to explain the most important research findings and the state of the standardization work in the field. The experimental part of the thesis consists of eight scientific publications and explains how they contribute to research in the field. Focus in on explaining how data transfer mechanisms have been improved from the application and networking layer points of views. Experimental methods for the Grid scenarios comprise of running a newly developed storage application on the existing research infrastructure. A network simulator is extended for the experimentation with challenging networking mechanisms in a network formed by mobile users. The simulator enables to investigate network behavior with a large number of nodes, and with conditions that are difficult to re-instantiate. As a result, recommendations are given for data retrieval and transfer design for the Grid and mobile networks. These recommendations can guide both system architects and application developers in their work. In the case of the Grid research, the results give first indications on the applicability of the erasure correcting codes for data storage and retrieval with the existing Grid data storage tools. In the case of the challenging networks, the results show how an application-aware communication approach can be used to improve data retrieval and communications. Recommendations are presented to enable efficient transfer and management of data items that are large compared to available resources