Reliable Server Pooling

Abstract: Reliable server pooling (RSP) allows a pool of redundant information sources to be viewed as a single transport endpoint and, therefore, it is able to provide persistent connections and balanced traffic for different applications. The Internet Engineering Task Force RSerPool Working Group has proposed an architecture to implement the RSP; it defines an overlay network providing an upper layer protocol or an application with a range of reliability services, from simple server selection to a fully automatic session-failover capability. The simulation experiments conducted in both wired and wireless environments show that the current version of the RSerPool works well in fixed and relatively reliable environments, but its performance worsens rapidly as the networks become more unreliable or mobile. The issues we have identified in wireless mobile ad hoc networks include network partition, high signaling overhead, difficulty in synchronization among name servers, and excessive aggressiveness in handling failures. Alternative design options for the RSP in wireless and mobile environments are introduced and evaluated.

Abstract: The Reliable Server Pooling effort (abbreviated "RSerPool"), provides an application-independent set of services and protocols for building fault tolerant and highly available client/server applications. This document provides an overview of the protocols and mechanisms in the reliable server pooling suite.

Abstract: The Reliable Server Pooling (RSerPool) architecture currently under standardization by the IETF RSerPool Working Group is an overlay network framework to provide server replication and session failover capabilities to applications using it. These functionalities as such are not new, but their combination into one generic, application-independent framework is. Initial goal of this thesis is to gain insight into the complex RSerPool mechanisms by performing experimental and simulative proof-of-concept tests. The further goals are to systematically validate the RSerPool architecture and its protocols, provide improvements and optimizations where necessary and propose extensions if useful. Based on these evaluations, recommendations to implementers and users of RSerPool should be provided, giving guidelines for the tuning of system parameters and the appropriate configuration of application scenarios. In particular, it is also a goal to transfer insights, optimizations and extensions of the RSerPool protocols from simulation to reality and also to bring the achievements from research into application by supporting and contributing relevant results to the IETF's ongoing RSerPool standardization process. To achieve the described goals, a prototype implementation as well as a simulation model are designed and realized at first. Using a generic application model and appropriate performance metrics, the performance of RSerPool systems in failure-free and server failure scenarios is systematically evaluated in order to identify critical parameter ranges and problematic protocol behaviour. Improvements developed as result of these performance analyses are evaluated and finally contributed into the standardization process of RSerPool.

Abstract: In this contribution we present a new type of mobility management for IP-based networks that, contrary to conventional approaches, does not focus on the network layer, but on the transport and session layers. At the heart of this new mobility concept is the reliable transport protocol SCTP, with an enhancement for dynamic address reconfiguration. The reliable server pooling (RSerPool) protocol suite provides a service for session monitoring and control. The suggested solution is transparent for applications, requires no changes in the network infrastructure, and is evaluated with a real-world implementation. Finally, we present first results from the application of this mobility concept to different mobility scenarios. These were obtained from working SCTP and RSerPool implementations that have been developed within our group.