International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California / The Consultative Committee for Space Data Systems (CCSDS) developed the CCSDS File Delivery Protocol (CFDP) to provide reliable delivery of files across space links. Space links are typically intermittent, requiring flexibility on the part of CFDP. Some aspects of that flexibility will be highlighted in this paper, which discusses the planned use of CFDP on the Global Precipitation Measurement (GPM) mission. The operational scenario for GPM involves reliable downlink of science data files at a high datarate (approximately 4 megabits per second) over a space link that is not only intermittent, but also one-way most of the time. This paper will describe how that scenario is easily handled by CFDP, despite the fact that reliable delivery requires a feedback loop.

International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Reliable delivery of data products is often required across space links. For example, a NASA mission will require reliable delivery of images produced by an on-board detector. Many missions have their own (unique) way of accomplishing this, requiring custom software. Many missions also require manual operations (e.g. the telemetry receiver software keeps track of what data is missing, and a person manually inputs the appropriate commands to request retransmissions). The Consultative Committee for Space Data Systems (CCSDS) developed the CCSDS File Delivery Protocol (CFDP) specifically for this situation. CFDP is an international standard communication protocol that provides reliable delivery of data products. It is designed for use across space links. It will work well if run over the widely used CCSDS Telemetry and Telecommand protocols. However, it can be run over any protocol, and will work well as long as the underlying protocol delivers a reasonable portion of the data. The CFDP receiver will autonomously determine what data is missing, and request retransmissions as needed. The CFDP sender will autonomously perform the requested transmissions. When the entire data product is delivered, the CFDP receiver will let the CFDP sender know that the transaction has completed successfully. The result is that custom software becomes standard, and manual operations become autonomous. This paper will consider various ways of achieving reliable file delivery, explain why CFDP is the optimal choice for use over space links, explain how the core protocol works, and give some guidance on how to best utilize CFDP within various mission scenarios. It will also touch on additional features of CFDP, as well as other uses for CFDP (e.g. the loading of on-board memory and tables).

International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California / The MESSENGER mission to Mercury will downlink data files via a protocol defined by the Consultative Committee for Space Data Systems (CCSDS) called the CCSDS File Delivery Protocol (CFDP). A reduced implementation of the protocol was developed for the spacecraft due to various system constraints and operational requirements. The software operates in conjunction with the playback features of the MESSENGER flight software allowing for the autonomous downlinking of files as well as providing for the management of the file system by the mission operations team. This paper presents the software implementation, metrics, and the lessons learned.

Denna uppsats behandlar ämnet filöverföring i ett nätverk. Fokus för arbetet har varit att undersöka MTU:ns inverkan på överföringshastigheten vid filöverföringar baserat på vilket protokoll som används och storleken på filerna som överförs. I arbetet har ett flertal experiment genomförts som syftat till att utreda detta, samt att finna vilket protokoll som överlag presterar bäst baserat på omständigheterna för överföringen. Olika filöverföringsprotokoll, fildistributionsprotokoll, MTU:er samt filstorlekar har testats för att finna vad som resulterar i högst överföringshastighet vid filöverföring över ett Ethernetnätverk. Resultaten visar på att en hög MTU uppnår högst överföringshastighet vid överföring av stora filer, men att en standard-MTU fungerar bättre för att överföra mycket små filer. / This report concerns the subject of file transfer. The focal point of the report is to study the effect that the MTU has on the speed of file transfers based on the protocol used and the size of the transferred files. During the course of the work, several experiments have been performed in order to determine this, as well as to find which protocol gives the overall best result based on the circumstances of the file transfers. Various file transfer protocols, file distribution protocols, MTUs and file sizes have been tested in order to find what results in the best file transfer speed over an Ethernet based network. The results show that a high MTU has the best performance when transferring large files, while a standard MTU gives better results for transferring very small files.

Thesis (M.S. in Computer Science)--Naval Postgraduate School, March 2004. / Thesis advisor(s): Wen Su, John Gibson. Includes bibliographical references (p. 189). Also available online.

Thesis (M.Sc.(Computer Science))--University of Pretoria, 2000. / Summaries in Afrikaans and English.

No description available.

Överföring eller mottagande av datorfiler är en syssla som de flesta av oss ägnar ossåt regelbundet i ett eller annat sammanhang, oavsett om det sker privat eller om detär arbetsrelaterat. File Transfer Protocol (FTP) är ett protokoll för just detta ändamålsom lanserades under tiden då persondatorer hade blivit allt vanligare i hemmetoch på arbetsplatsen. Sedan dess har flera andra protokoll introducerats och i dagslägetfinns det flertalet valmöjligheter tillgängliga, alla med sina unika såväl som gemensammaegenskaper. Simple Mail Transfer Protocol (SMTP) kompletterad medMIME-standarden är ett populärt alternativ till de renodlade filöverföringsprotokollenpå grund av användarnas bekantskap och tidigare erfarenheter med e-posttjänster.Att skicka och ta emot filer via e-post innebär dock vissa begränsningar samt att vissasäkerhetsaspekter måste tas i beaktande, i synnerhet för företagsanvändare som dagin och dag ut måste hantera känslig data. I denna uppsats har tre olika filöverföringsprotokoll(SFTP, SMTP och HTTP) utvärderats ur ett användarvänlighetsperspektivsåväl som ett säkerhetsperspektiv. Resultatet indikerar att HTTP(S) tillsammans meduttökningen WebDAV kan anses vara ett lämpligt alternativ för organisationer somsamtidigt är enkelt att använda. De övriga protokollen, SMTP och SFTP, har ocksåsina användningsområden där SFTP verkar vara mer tilltalande för avanceradeanvändare och där SMTP förblir ett gångbart alternativ för privat bruk av mindreavancerade användare under vissa förutsättningar. / Transferring and receiving computer files are something most of us do on a regularbasis whether it is for private purposes or if it is work related. FTP is a protocolused for this very purpose which was launched during a time when personal computerswere growing increasingly popular in both home and workplace environments.Since then, more protocols have been introduced and today there are a number ofoptions available bringing new and common features alike to the market. The SMTPprotocol, extended with the MIME standard, is currently a widely used alternative tothe pure file transfer protocols due to the user familiarity and past experiences withthese mail services. Sending and receiving files through e-mail does however implysome limitations together with the fact that some security aspects need to be takeninto consideration, particularly for company users handling sensitive data. In thisthesis, three different file transfer protocols (SMTP, SFTP and HTTP) have all beenevaluated in account of their user friendliness as well as their security features. Theresults indicate that HTTP(S) combined with the WebDAV extension can be considereda viable alternative for organizations due to its user friendliness and security.The remaining protocols, SMTP and SFTP, also have their uses where SFTP wouldseem to be an appealing option for advanced users and where SMTP remains a passablealternative for private usage by regular users under the right conditions.

Our work focuses on performance modelling of TCP-controlled file transfers in infrastructure mode IEEE 802.11 wireless networks, and application of the models in developing association schemes. A comprehensive set of analytical models is used to study the behaviour of TCP-controlled long and short file transfers in IEEE 802.11 WLANs. The results can provide insight into the performance of TCP-controlled traffic in 802.11 WLANs in a variety of different network environments. First, we consider several WLAN stations associated at rates r1, r2, ...,rk with an Access Point. Each station (STA) is downloading a long file from a local server, located on the LAN to which the AP is attached, using TCP. We assume that a TCP ACK will be produced after the reception of d packets at an STA. We model these simultaneous TCP-controlled transfers using a semi-Markov process. Our analytical approach leads to a procedure to compute aggregate download as well as per-STA throughputs numerically, and the results match simulations very well. Performance analysis of TCP-controlled long file transfers in a WLAN in infrastructure mode is available in the literature with one of the main assumptions being equal window size for all TCP connections. We extend the analysis to TCP-controlled long file uploads and downloads with different TCP windows. Our approach is based on the semi- Markov process considered in above work, but with arbitrary window sizes. We present simulation results to show the accuracy of the analytical model. Then, we obtain an association policy for STAs in an IEEE 802.11 WLAN by taking into account explicitly an aspect of practical importance: TCP controlled short file downloads interspersed with read times (motivated by web browsing). Our approach is based on two steps. First, we consider the analytical model mentioned above to obtain the aggregate download throughput. Second, we present a 2-node closed queueing network model to approximate the expected average-sized file download time for a user who shares the AP with other users associated at a multiplicity of rates. These analytical results motivate the proposed association policy, called the Estimated Delay based Association (EDA) policy: Associate with the AP at which the expected file download time is the least. Simulations indicate that for a web-browsing type traffic scenario, EDA outperforms other policies that have been proposed earlier; the extent of improvement ranges from 12.8% to 46.4% for a 9-AP network. We extend the performance model by considering _le sizes drawn from heavy-tailed distributions. We represent heavy-tailed distributions using a 1 mixture of exponential distributions (following Cox's method). We provide a closed queueing network model to approximate the expected average-sized file download time for a user who shares the AP with other users associated at a multiplicity of rates. Further, we analyze TCP-controlled bulk file transfers in a single station WLAN with nonzero propagation delay between the file server and the WLAN. Our approach is to model the flow of packets as a closed queueing network (BCMP network) with 3 service centres, one each for the Access Point and the STA, and the third for the propagation delay. The service rates of the first two are obtained by analyzing the WLAN MAC. We extend this work to obtain throughputs in multirate scenarios. Simulations show that our approach is able to predict observed throughputs with a high degree of accuracy.

This master thesis is mainly focused on the backup systems and describes each individual backup techniques in detail. Next main point of this thesis, is explaining functionality of IPv4 and FTP, which are closely related to the topic. Outcome is a backup application written in Java language, which is capable of backup files on FTP server or on local/ network storage area. Backup application also allows settings for automatic backup and restoring files from the storage area. Finally there was made a measurment, where were point out advantages and disadvantages of transfer mediums and where was practically shown a logic of creating the backup system. Goal was a creation of multiplatform backup application.