Controlling the Tempest: adaptive management in advanced ATM control architectures

Research in ATM management has delegated control functions from the ATM switch into higher level open control architectures. For example, functions such as call admission control are implemented within such a control architecture rather than as an integral part of the switch. The association between the switch fabric and the switch control functions is made less strict, allowing, for example, a single entity to perform routing for a group of switches. This greater flexibility in the provision of control is accompanied by an increase in complexity resulting from the possibility of making control decisions remotely from the controlled network element. The location of the controller in relation to the fabric is not just an implementation issue; it has a large impact on the way we handle traditional operation and maintenance (OAM) functions. For example, recovering from partial failure of the network is problematic when the controlling entity is communicating with the switch it controls across that same network. Most research into such control architectures has concentrated on the advantages of increasing flexibility; little work has looked at how the traditional techniques for creating robust networks can be adapted for use in this environment. Mobile software agents can move to where their functions are carried out. When an agent has moved across the network, it executes its function there. The function will not fail due to network problems. They can also reduce the amount of management state that needs to be carried across the network for control purposes. This is important when recovering from failure since the network is stressed and minimal expectations should be placed on its behavior. We show how mobile agents can be used within an open control architecture in order to implement robust operation and maintenance functions. We explain in some detail our work in implementing one such function.