Robert James Mitchell

Network attack visualization and response through intelligent icons

Determination of appropriate response to information system attack is jointly determined by confidence of classification, nature (type) of attack, and confidence in effectiveness of response. In this paper we present a technique to rapidly assess similarity of observed behavior to attack or normal models: displaying the similarity of observed data to learned Minimum Description Length Models for normal and attack behaviors using “intelligent icons”. These icons provide a visual indication of similarity to normal and attack signatures and can alert human operators to the key motifs and signatures that affect confidence in classification and indicated response.

A partitioned implementation of the Xpress Transfer Protocol. I

This paper focuses on the practical aspects of implementing the Xpress Transfer Protocol (XTP). A strategy is proposed for partitioning XTP across host and off-board processors in a distributed system in which an existing XTP implementation is changed in a step-wise fashion to meet the system requirements. The architecture is described, and the XTP development strategy is presented. Finally, XTP performance and integration issues are discussed.<<ETX>>

A Multi-Band Random Access Messaging Protocol

Media access protocols can be classified as either demand assigned or random access. Demand assigned protocols are often inflexible, inefficient under diverse traffic, and do not scale well to large networks. Random access schemes usually suffer from collisions and cannot manage the multi-frequency capabilities of many radios. We present new results on our pseudorandom message scheduling approach. The protocol has been extended to manage multiple frequency channels. In dense networks, sub-networking can be performed. Nodes are partitioned a priori and are assigned different reference frequencies for their discovery/broadcast segments. We demonstrate in networks where nodes use transmission based start times along with conventional carrier sense channel access, collision free communications

Satellite teleradiology test bed for digital mammography

Teleradiology offers significant improvement in efficiency and patient compliance over current practices in traditional film/screen-based diagnosis. The increasing number of women who need to be screened for breast cancer, including those in remote rural regions, make the advantages of teleradiology especially attractive for digital mammography. At the same time, the size and resolution of digital mammograms are among the most challenging to support in a cost effective teleradiology system. This paper will describe a teleradiology architecture developed for use with digital mammography by GE Corporate Research and Development in collaboration with Massachusetts General Hospital under National Cancer Institute (NCI/NIH) grant number R01 CA60246-01. The testbed architecture is based on the Digital Imaging and Communications in Medicine (DICOM) standard, created by the American College of Radiology and National Electrical Manufacturers Association. The testbed uses several Sun workstations running SunOS, which emulate a rural examination facility connected to a central diagnostic facility, and uses a TCP-based DICOM application to transfer images over a satellite link. Network performance depends on the product of the bandwidth times the round- trip time. A satellite link has a round trip of 513 milliseconds, making the bandwidth-delay a significant problem. This type of high bandwidth, high delay network is called a Long Fat Network, or LFN. The goal of this project was to quantify the performance of the satellite link, and evaluate the effectiveness of TCP over an LFN. Four workstations have Suns HSI/S (High Speed Interface) option. Two are connected by a cable, and two are connected through a satellite link. Both interfaces have the same T1 bandwidth (1.544 Megabits per second). The only difference was the round trip time. Even with large window buffers, the time to transfer a file over the satellite link was significantly longer, due to the bandwidth-delay. To compensate for this, TCP extensions for LFNs such as the Window Scaling Option (described in RFC1323) were necessary to optimize the use of the link. A high level analysis of throughput, with and without these TCP extensions, will be discussed. Recommendations will be made as to the critical areas for future work.

Experience with a proposed teleradiology system for digital mammography

Teleradiology offers significant improvement in efficiency and effectiveness over current practices in traditional film/screen-based diagnosis. In the context of digital mammography, the increasing number of women who need to be screened for breast cancer, including those in remote rural regions, make the advantages of teleradiology especially attractive for digital mammography. At the same time, the size and resolution of digital mammograms are among the most challenging to support in a cost effective teleradiology system. This paper describes a teleradiology architecture developed for use with digital mammography by GE Corporate Research and Development in collaboration with Massachusetts General Hospital under National Cancer Institute (NCI/NIH) grant number R01 CA60246-01. Experience with a testbed prototype is described. The telemammography architecture is intended to consist of a main mammography diagnostic site serving several remote screening sites. As patient exams become available, they are forwarded by an image server to the diagnostic site over a WAN communications link. A radiologist at the diagnostic site views a patient exam as it arrives, interprets it, and then relays a report back to the technician at the remote site. A secondary future scenario consists of mobile units which forward images to a remote site, which then forwards them to the main diagnostic site. The testbed architecture is based on the Digital Imaging and Communications in Medicine (DICOM) standard, created by the American College of Radiology (ACR) and National Electrical Manufacturers Association (NEMA). A specification of vendor-independent data formats and data transfer services for digital medical images, DICOM specifies a protocol suite starting at the application layer downward, including the TCP/IP layers. The current DICOM definition does not provide an information element that is specifically tailored to mammography, so we have used the DICOM secondary capture data format for the mammography images. In conclusion, experience with the testbed is described, as is performance analysis related to selection of network components needed to extend this architecture to clinical evaluation. Recommendations are made as to the critical areas for future work.

Experience with an XTP implementation for embedded systems

An implementation of the XTP protocol is discussed relative to the embedded systems environment. An overview of the embedded system architecture and unique design constraints is followed by a description of the protocol development environment. The original development approach is presented with a critique based on experience thus far. Embedded system implementation and protocol development issues experienced in this type of environment and proposed solutions are presented to provide a framework for similar development efforts.<<ETX>>