Tsipora P. Barzilai

Design and implementation of an RSVP-based quality of service architecture for integrated services Internet

The paper presents the design and implementation of a quality of service architecture for the Internet. The architecture is based on the emerging standards for resource reservation in the Internet, namely the RSVP protocol and the associated service specifications defined by the Internet Engineering Task Force. Our architecture represents a major functional enhancement to the traditional sockets based communication subsystem, while preserving application programming interface and binary compatibility with existing applications. It is scalable and supports a variety of network interfaces ranging from legacy LAN interfaces, such as token ring and Ethernet, to high speed ATM interfaces. We also describe our initial experiences with the implementation of this architecture on the IBM AIX platform.

Performance issues in WWW servers

This paper evaluates techniques for improving operating system and network protocol software support for high-performance World Wide Web servers. We study approaches in three categories: i.e., new socket functions, per-byte optimizations, and per-connection optimizations. We examine two proposed socket functions, i.e., acceptex( ) and send_file( ), comparing send_file( )s effectiveness with a combination of mmap( ) and writev( ). We show how send_file( ) provides the necessary semantic support to eliminate copies and checksums in the kernel, and quantify the benefit of the functions header and close options. We also present mechanisms to reduce the number of packets exchanged in an HTTP transaction, both increasing server performance and reducing network utilization, without compromising interoperability. Results using WebStone show that our combination of mechanisms can improve server throughput by up to 64%, and can eliminate up to 33% of the packets in an HTTP exchange. Results with SURGE show an aggregate increase in server throughput of 25%.

Design and implementation of an RSVP-based quality of service architecture for an integrated services Internet

The Internet Engineering Task Force (IETF) is currently in the process of overhauling the architecture of the Internet to meet new challenges and support new applications. One of the most important components of that venture is the enhancement of the Internet service model from a classless best effort service architecture to an integrated services architecture supporting a multitude of classes and types of services. This paper presents the design, implementation, and experiences with a protocol architecture for the integrated services Internet. It is based on the emerging standards for resource reservation in the Internet, namely, the RSVP protocol and the associated service specifications defined by the IETF. Our architecture represents a major functional enhancement to the traditional TCP/IP protocol stack. It is scalable in terms of performance and number of network sessions, and supports a wide variety of network interfaces ranging from legacy LAN interfaces, such as Token Ring and Ethernet, to high-speed ATM interfaces. The paper also describes the implementation of this architecture on the IBM AIX platform and our experiences with the system. We then present a performance analysis of the system which quantifies the overheads imposed by all components of the QoS support, such as traffic policing, traffic shaping, and buffer management.

Reliable multiuser tree setup with local identifiers

The authors present a reliable protocol for setting up a tree connection for the purpose of multicast communication over a high-speed packet switched network. The tree connection is based on the use of local identifiers that are swapped at every intermediate node of the tree. Local identifiers are simple to manage, provide fast access to the routing tables, and are very efficient in terms of the size of the resulting routing space. The context of the present work is a high-speed network in which the local label swapping on data messages is performed in hardware by the switching subsystem, while the connection setup is done in software by the switch control subsystem. The correctness of the protocol is formally proved. The protocol ensures the integrity of the tree, and, when failures occur, the tree is gracefully degraded into a smaller tree. >

A video conferencing testbed on ATM: design, implementation and optimizations

This paper describes our experiences with the design and implementation of a very high-end video conferencing testbed on an ATM network. Our system is built on an IBM RISC System/6000 equipped with prototype hardware for video and audio capture and compression, and an IBM 100 Mb/s ATM adapter. In our early experiments we used UDP/IP running over ATM Adaptation Layer 5 (AAL5) for data transfer between peers. Our initial experiences with the system indicated that the overall system performance did not match our expectations even though most of the video, audio, and network processing was performed in hardware. A thorough profiling of the system revealed that the protocol processing and data handling overheads in the end-host are responsible for the poor video/audio quality. Based on these observations, we have proposed and implemented changes to the protocol data path that can significantly improve the performance of the system. Although we discuss our solution in the context of a video conferencing application, our approach is general and can be applied to many other applications. It is particularly useful for applications that are required to handle large volumes of time-critical data, such as multimedia servers.

Implementing System/36 advanced peer-to-peer networking

System/36 Advanced Peer-to-Peer Networking (APPN) provides highly dynamic, fully distributed peer networking for low-end processors. It is built upon existing SNA Logical Unit 6.2 and Node type 2.1 support. APPN presents System/36 users with a simplified model of communications. The structure of the APPN subsystem is outlined, with particular emphasis on the integration of APPN functions with existing SNA support. The authors describe how particular aspects of the APPN design have been tuned to the System/36 operating environment.

Supporting timing and requirements of digital video and audio in desktop conferencing systems

Digital video and audio are an integral part of a desktop collaboration system. In order to provide an integrated collaboration environment which supports text, graphics, video, and audio, it is necessary to effectively support the timing requirements of digital video and audio. This paper describes the mechanisms and provisions required to support real-time audio and video streams. Details of the Multimedia Multiparty Teleconferencing (MMT) system are described to illustrate these issues with a working implementation. The communication and processing paths of the audio and video streams through the system are described. Finally, tradeoffs between different possible solutions are discussed with regard to those issues (e.g. bandwidth, delay, synchronization, etc.) which are particularly important for real-time multimedia applications.

Reliable multi-user tree setup with local identifiers

A protocol for setting up a tree connection for the purpose of multicast communication over a high-speed packet switched network is presented. The tree connection is based on the use of local identifiers, which are swapped at every intermediate node of the tree. Local identifiers are simple to manage, provide fast access to the routing tables, and are very efficient in terms of the size of the resulting routing space. The authors consider a high-speed network in which the local label swapping on data messages is performed in hardware by the switching subsystem, while the connection set-up is done in software by the switch control subsystem. A reliable protocol for setting up the tree connection is presented, and its correctness is formally proved. The protocol ensures the integrity of the tree and when failures occur, it is gracefully degraded into a smaller tree.<<ETX>>