Stefan Wahl

Measurement of the SIP parsing performance in the SIP express router

Future telephony and multimedia systems will use the Session Initiation Protocol (SIP) for signaling purposes. SIP is a text-based protocol that imposes challenges for an efficient message processing. The ability of SIP entities to process SIP messages quickly is crucial for the performance of these networks, which often have strict timing requirements, e. g., to keep the call setup delays small. This paper studies the performance of SIP message processing in SIP proxies, focusing mainly on the impact of message parsing. We perform a detailed delay analysis for the widely used SIP Express Router (SER). Our measurements show that message parsing actually contributes significantly to a SIP proxys processing efforts, and therefore confirm other existing studies. However, our results also show that the overall delay in high-performance SIP proxies is stronger affected by other factors, in particular the operating system.

Enhanced Methods for SIP based Session Mobility in a Converged Network

The worlds of fixed and mobile networks are merging towards fixed mobile converge (FMC). This process brings many challenges to networking technologies to support an optimal level of security, QoS and mobility across heterogeneous fixed and mobile access networks. Efficient mobility management mechanism able to provide desired level of mobility is one of the key issues in FMC development. This paper presents enhanced methods for SIP based session mobility that brings continuous mobility, privacy protection and interdomain mobility across access and core networks possibly managed by different providers. This paper is organized as follows. First an overview of the standard SIP mobility mechanisms is given with its advantages and drawbacks. Afterwards, the SIP controlled IP soft handover concept is proposed as the method to overcome standard SIP mobility shortcomings. Finally a conclusion is given.

Load Sharing in a Distributed IMS Architecture

The IP Multimedia Subsystem (IMS) serves as universal platform for fast and standardized creation of mobile services. Typical deployment models for the IMS favor centralized session control and application servers. Furthermore, they rely on sophisticated border elements for, e.g., policy enforcement. One step towards a simpler architecture is the integration of call control, application server, and media functions into border elements. This leads to a distributed IMS architecture with equal processing nodes, which drastically reduces system complexity and scales on functional module instantiation basis. However, the distributed nature of the architecture reduces the statistical gain. In this work, we study a suitable load sharing concept that counters or even over-compensates this problem. In principle, this mechanism realizes one large virtual central server with small control and message overhead. Our simulative evaluation shows the feasibility and performance of our approach. I. INTRODUCTION

Architecture and experiences of a multi-service HFC network

This paper describes the implementation and validation in field trials of an ATM based HFC access network providing quality of service for native ATM applications and legacy IP applications. Native ATM applications are supported by switched virtual connections allocating dedicated resources in the HFC network. IP applications are enriched with QoS in the HFC network by adopting the differentiated services strategy defined by IETF. The developed and hardware-implemented MAC controller supports several service classes and is capable of distributing non-preallocated upstream bandwidth in a fair way to the bandwidth requesting cable modems by simultaneous respecting the priorities of the service classes.

Realization of an ATM-based HFC demonstrator with high upstream capacity

Within the framework of the ACTS project ATHOC (ATM applications on Hybrid Optical fiber Coax), cable TV modems and hybrid fibre coax (HFC) systems have been realized, demonstrating the basic technologies which are common to the different HFC standardisation work-groups. The ATHOC prototypes employ 64-QAM modulation for the downstream and burst mode QPSK modulation for the upstream transmission, respectively, in order to achieve 40 Mb/s and 3 Mb/s. Time division multiple access (TDMA) is the method which is implemented to give all users access to the shared medium of the tree-and-branch CATV network. The article clarifies the HFC system concept which was implemented. The functions of the access network adaptation in the headend and the access network termination at the users premises are described.

Implementation of access priorities in the medium arbitration of HFC system

The design of a dynamic MAC protocol to arbitrate the common medium in a hybrid fiber coaxial system providing service differentiation and enhanced QoS capabilities as well as the implementation, testing and verification of the MAC controller are described in this paper. The MAC protocol employs four access priorities and a flexible reservation scheme. The MAC controller was implemented mainly in hardware to execute all real-time operations and was integrated in the AROMA HFC system, which is shown. Various group tests were carried out using the lab demonstrator of the system to assess the system performance and verify that the developed implementation meets the design objectives concerning QoS differentiation.

Provision of QoS for Legacy IP Applications in an ATM-over-HFC Access Network

With the increasing needs for delivering higher bandwidths to residential areas, new technologies (e.g. xDSL) are emerging that are enabling broadband access. Network technologies, which are based upon upgrades of existing network infrastructures, are, economically, one of the most promising approaches. One of these, competing with several other approaches, is hybrid fibre coax networks (HFC) currently being used for CATV broadcasting. The various access network technologies will be interconnected via broadband core networks resulting in heterogeneous networks which, have to provide end-to-end applications based on the Internet Protocol. Since the CATV network is of a shared nature, the provisioning of IP-based Quality of Service (QoS) requires suitable inter-layer signalling in order to provide QoS-related information as soon as possible to the relevant instances. This paper presents a system architecture using ATM-over-HFC for high-speed Internet access providing IP-based QoS. The architectures seamless interoperability with other network technologies supports both IP-based and native ATM applications.