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NPS is a real-time network engine provided by RealTime Mach for real-time applications and distributed multimedia systems. NPS provides a framework for implementing real-time network protocols which are able to bound end-to-end delay and throughput. Real-Time Mach also provides a framework to select the suitable implementations of a network protoco...
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... Besides the options in the specification — such as loose source routing, record route and Internet timestamp — IPv4 options have recently and in the past been proposed for several other custom extensions. A small and non-exhaustive list of these extensions include: conveying information between different layers in the networking stack [2], providing quality of service in ad hoc networks [3], propagating the priority of a real-time media stream to a receiver [4], as method of enabling Active Networks [5], [6] and for multicast schemes [7], [8]. Also, there is currently an active Internet-draft (expires September 2004) that proposes an experimental enhancement of path MTU discovery using options [9]. ...
IP version 4 specifies options that extend the basic IP header and also allow new functions to be added to IP without breaking existing implementations. Since options must always be inspected at routers, it is generally believed that routers prioritize ordinary packets over packets carrying options in a way that significantly impacts the performance of options. This article presents an experiment based on end-to-end probing using UDP packets, capturing the performance penalties associated with IPv4 options. Analysis of experiment results quantifies the impact of IPv4 options on forwarding performance in terms of delay, jitter and loss rate. From the analysis it can be concluded that there is a slight increase in delay and jitter and a severe increase in loss rate.
... We implemented a distributed QuickTime movie player, QtPlay[8, 16] which retrieves movie data from disks using CRAS and transmits it over the network using NPS[9]. QtPlay sends video streams to the X11 server and audio streams to an audio server for playback, and it can play multiple movies simultaneously . ...
This paper presents the design and implementation of a simple continuous media storage server: CRAS on Real-Time Mach. CRAS is a specially optimized storage system for retrieving multiple continuous media streams such as audio and video from a disk at constant rates for small scale distributed multimedia systems. Many previous continuous media storage servers have focussed on high throughput for supporting as many video sessions as possible. However, these servers are too big and complicated for playback applications that retrieve continuous media data from the local disks of personal computers. Also, there are many continuous media systems requiring small continuous media storage servers that can be shared by a small number of applications. To reduce hardware costs, the servers should run on less powerful computers. This means that the previous big and complicated servers are not appropriate for such small scale environments. We show that our simple continuous media server for small scale systems can guarantee the retrieval of continuous media data at a constant rate, and provide high throughput even though it is compact and simple.
... In this section, we describe a brief overview of Real- Time Mach, NPS and CRAS, which are used to implement our distributed video player. The detailed information of these systems are found in [9, 10, 11, 12, 17, 18]. Currently, Lites[5] , which is a Unix server providing binary compatibility of FreeBSD, is running on Real-Time Mach. ...
... In a word, the stream with the least importance value, whose current QOS value is more than its minimum QOS value, is degraded when a new session is created or system becomes overloaded. QtPlay provides a dynamic QOS control scheme for accepting more streams, since an amount of resources used by current applications may be decreased for accepting a new application[11]. In the current implementation, QtPlay changes the QOS level of a movie dynamically by detecting the violation of timing constraints of movies instead of using missed deadline notication described in [11]. ...
... QtPlay provides a dynamic QOS control scheme for accepting more streams, since an amount of resources used by current applications may be decreased for accepting a new application[11]. In the current implementation, QtPlay changes the QOS level of a movie dynamically by detecting the violation of timing constraints of movies instead of using missed deadline notication described in [11]. Each stream of QtPlay decreases its frame rate when obsolete video frames and audio samples are detected. ...
Real-time system and continuous media system researchers have worked in areas that are considered by each to be unrelated to the other's domain although continuous media system researchers agree with the effectiveness of real-time technologies on continuous media systems. Media control techniques for improving the smoothness of continuous media such as jitter control and inter-stream synchronization schemes are developed for smoothing continuous media streams running on traditional timesharing operating systems. On the other hand, real-time system researchers show the effectiveness of real-time technologies for satisfying timing constraints of the continuous media. However, there is no report to showing the effectiveness of real-time technologies for the media control techniques. This paper describes experiences with building a continuous media application on Real-Time Mach. First, we present the structure of our distributed video player, called QtPlay, and its media control techniques for smoothing continuous media streams, then we show the effectiveness of real-time technologies for the media control techniques
... Besides the options in the specification, such as loose source routing, record route and Internet timestamp, IPv4 options have recently and in the past been proposed for several other custom extensions. A small and non-exhaustive list of these extensions include: conveying information between different layers in the networking stack [55], providing quality of service in ad hoc networks [37], propagating the priority of a real-time media stream to a receiver [42], as method of enabling Active Networks [7,54] and for multicast schemes [44,47]. The existence of these proposals show that even though ip-options were conceived over two decades ago, there still exists the need for their functionality. ...
