Abstract

Telecom service providers are augmenting telephony networks with packetswitched networks, enabling converged voice, data, and multimedia transport over a single network infrastructure. However, the profound mismatch between circuit-switched telephony networks and packet-switched data networks makes providing converged voice and data services difficult. Voice over packet (VoP) services such as voice over Internet protocol (VoIP) must deliver the same high reliability and quality of service as the public telephone network while compensating for packet overhead, delay, jitter, and loss. 1,2 VoP services require extensive signal processing for echo cancellation, voice coding, and modems. They also require packet relay services for signaling, tones, fax, and modem data. VoP and media gateways 3 adapt voice, data, and multimedia traffic to work for different network types and provide packet-based services. Because services vary dynamically with each voice channel, gateways must support many different services concurrently and in real time. Gateway capacities range from tens to tens of thousands of voice channels. Calisto integrates the components of a multichannel gateway into a single-chip lowpower communications platform that uses multiprocessor parallelism supported by extensive on-chip memory systems. Its power efficiency and programmability enable high channel density and flexibility, achieving 30 times the density of prior designs within existing power and volume envelopes. Telecom providers are deploying two generations of Calisto architecture, the Broadcom BCM1500 and BCM1510, in enterprise and carrier-class communications systems. Multichannel communications gateway We designed the Calisto platform to meet the requirements of multiple gateway applications, including • VoIP, voice over asynchronous transfer mode (ATM), voice over digital subscriber line (DSL), and voice over cable; • media gateways and servers; • trunking, 3G wireless, and cable and DSL gateways; • remote access servers;

No abstract

MiThOS (Micro-kernel Threads Operating System)is an experimental operating system for embedded sys-tems. The system kernel is a first implementation of the POSIX "Minimal Real-Time Sgstem Profile". It is based on prior work of a library implementation of Pthreads (POSIX threads). The system is fully preemptive. It supports multi-threading within a single process environment with shared kernel and user space, i.e. real-time tasks are mapped onto POSIX threads. It exhibits remarkable timing predictability intended for hard real-time requirements. This is achieved b y a careful design of only f e w device drivers. The system has been implemented and tested on the SPARC V M E architecture. The system includes a fast contezt switching algorithm for the SPARC which outperforms the context switch under SunOS and matches the performance under Solaris. It supports selective enabling and disabling of hardware components (MMU, caches, etc.) since its sources are available. Furthermore, an implementation-defined extension of POSIX threads for deadline scheduling is presented. Overall, the system exhibits slightly faster performance than SunOS 4.x and is considerably more predictable in its timing behavior. Applications of the kernel range from evaluating the overhead of new language features in Ada 95 and its runtime system, verifying static timing predictions on a bare machine, to providing the operating system for small embedded system that require a high timing predictability.

This paper describes experience prototyping the proposed IEEE standard "minimal realtime system profile", whose primary component is support for realtime threads. It provides some background, describes the implementation, and reports preliminary performance measurements.