W. Almesberger

SRP: a Scalable Resource Reservation Protocol for the Internet

Current resource reservation architectures for multimedia networks do not scale well for a large number of flows. We propose a new architecture that automatically aggregates flows on each link in the network. Therefore, the network has no knowledge of individual flows. There is no explicit signalling protocol, and the protocol overhead mainly consists an the introduction of a packet type with three values (reserved, request or best-effort) which can be encoded on two bits.

SRP: a scalable resource reservation protocol for the Internet

Current resource reservation architectures for multimedia networks do not scale well for a large number of flows. We propose a new architecture that automatically aggregates flows on each link in the network. Therefore, the network has no knowledge of individual flows. There is no explicit signalling protocol, and the protocol overhead mainly consists in the introduction of a pocket type with three values (reserved, request or best-effort) which can be encoded on two bits.

Using quality of service can be simple: Arequipa with renegotiable ATM connections

We have modified the popular Mbone tool vic (VIdeo Conferencing) to use Arequipa (Application REQuested IP over ATM). The latter enables applications and in particular vic, to request a direct ATM connection for its exclusive use and to directly control the traffic parameters of this connection. We have also implemented ATM Forum`s UNI4.0 signaling and ITU-T`s connection modification recommendation Q.2963.1, on end-systems as well as on switches. This implementation, coupled with the Arequipa mechanism, allowed vic to negotiate and renegotiate ATM bandwidth at will, at run time. We describe how vicaccomplished that over the ATM WAN of SWISSCOM, transferring live video from Lausanne to Basel and Zurich over switched, renegotiable ATM connections. To our knowledge, this was the first time any application had the capacity to tune ATM traffic parameters at run time.

Quality of Service (QoS) in Communication APIs

This paper gives an overview of the mechanisms that currently specified APIs (for Native ATM and for RSVP) provide to applications for the purpose of controlling QoS parameters. It compares the abstractions they provide with respect to application needs and modern operating system practices. Furthermore, it discusses what extensions or modifications would be desirable in future APIs.

High-speed ATM networking on low-end computer systems

The practicability of high-speed communication on low-end systems has frequently been questioned and even less demanding variants of high-speed networking standards have been developed to accommodate for the restrictions of contemporary personal computers. In this paper, architectural aspects of existing PC hardware, ATM network adapters, and operating systems are examined, and in fact, serious limitations are discovered. Primarily memory bandwidth is found to be insufficient to support the number of transfers required by traditional networking implementation designs, plus the number of further accesses required for data processing by the sending or the receiving application. The use of single-copy, a concept well known from higher-end systems, is proposed as a means to overcome the memory bandwidth bottleneck. Not only usage scenarios in which single-copy can be reasonably applied, but also situations in which single-copy would yield only marginal improvements or where performance could even deteriorate are identified. Furthermore, implementation issues, such as locking of shared user pages, are discussed. Finally, the performance of single-copy is tested in an implementation of ATM support on Linux, done at LRC, by measuring uni- and bidirectional AAL5 throughput with different PDU sizes. The measurement results indicate that high-speed communication is feasible on todays low-end systems for applications which are primarily uni-directional in nature, and which respect alignment and access constraints imposed by optimizations like single-copy.

Quality of Service Renegotiations

Giving users simple access to QoS selection capability of ATM networks is important for the future of integrated services networks. We describe the first instance of an application in which users had the capacity to tune ATM traffic parameters with a button, at run time. To achieve this we implemented the necessary signaling extension on ATM switches as well as on end-systems. Furthermore, we extended Arequipa to support modification, and modified the popular Mbone tool Vic to use Arequipa to request and modify ATM bandwidth at will. We describe how Vic accomplished this over the ATM WAN of SWISSCOM, transferring live video from Lausanne to Basel over switched, renegotiable ATM connections.