The Tempesta Framework for Safe , Resource Assured , Programmable

Most research in network programmability has stressed the exibility engendered by increasing the ability of users to conngure network elements for their own purposes, without addressing the larger issues of how such advanced control systems can coexist both with each other and with more conventional ones. The Tempest framework presented here extends beyond the provision of simple network programmability to address these larger issues. In particular we show how network programmability can be achieved without jeopardizing the integrity of the network as a whole, how network programmability ts in with existing networks and how programmability can be ooered at diierent levels of granularity. Our approach is based on the Tempest's ability to dynamically create Virtual Private Networks (VPNs) over a switched transport architecture, e.g. an ATM network. Each VPN is assigned a set of network resources which can be controlled using either a well known control system or a control system tailored to the speciic needs of a distributed application. The rst level of programmability in the Tempest is fairly course grained: an entire virtual network can be programmed by a third party. At a ner level of granularity the Tempest allows user supplied code to be injected into parts of an operational virtual network, thus allowing application speciic customisation of network control. The paper shows how the Tempest framework allows these new approaches to coexist with more conventional solutions.