Management Software for Protocol-level Adaptations in Dependable Network Services

The paper describes a management model where aservice provider (SP) maintains multiple protocol modules to exercisethe infrastructure resources (e.g., bandwidth and processing cycles) under various environment conditions. Here, each protocol exhibitsa certain degree of performance optimality and service resiliencein distinct operating regions of the network infrastructure and theenvironment. At run-time, the SP selects one of the protocol modulesthat can meet the client-requested Quality of Service (QoS) obligationagainst the prevailing operating conditions. Under 'normal' conditionswhen the external disturbances are benign and of low intensity(e.g., low packet loss in the network), an optimal usage of the networkresources is important. Under hostile conditions however (such as sub-system outages and failures), a sustained access to the networkservice at some minimum acceptable level becomes more important. Accordingly, a protocol selection by the SP considers the tradeoffbetween service availability under extreme operating conditions andresource optimality under normal operations. Our model allows adynamic switching from one protocol module to another at run-timebased on the changing environment conditions. The paper describessoftware engineering oriented case studies to exemplify the protocolswitching as a foundation to build dependable network services.