MUM Architecture
MUM proxy-based architecture is aimed to extend traditional client-server solution with the interposition of proxy nodes that realize several facilities to support continuous sevices delivery in the Wireless Internet. This architecture guideline permits to introduce proxies whenever in need over the service path, in order to flexibly handle and adapt multimedia flow delivery, without leaving the whole management burden to client/server end-nodes. The service path involves the client, the server and all the proxy active components participating in service delivery.
To activate and assist proxy active components at intermediate nodes MUM middleware realizes several facilities at intermediate nodes as better explained in the following.
Architecture
Figure 1: System Layering.
The Mechanisms Layer realizes the basic middleware mechanisms on which the more complex services, that are part of the MW Facilities Layer, stand. Here there is a list of the services included in this layer:
- Location Service: provides location awareness to the upper layer, using the location abstractions introduced by SOMA and organizing them in a tree;
- Software Manager: memorizes the downloaded code (on each node it is present one repository) and the active components;
- Resource Manager: reserve and monitor the needed resources for each single node (CPU time so far);
- Profile and Metadata Manager: there is one centralized server that maintains presentations’ metadata and another one that maintains users’ profiles.
This lower layer was implemented using only standard C/S solutions because we think that MA paradigm is a powerful means that must be used only when necessary, that is for the realization of MUM most dynamic services.
The Facilities Layer includes the strategies and the most dynamic parts of MUM; MAs where employed here for their properties of autonomy and dynamicity. Moreover, using MAs it is really simple to change and try different strategies, as they can be encapsulated in the agent itself.
The services at this layer are the following:
- Downloading: downloads the necessary code in each node; this service was realized as an agent that encapsulates the strategies to search and download code within the system;
- Configuration: configures the service path, encapsulating also QoS negotiation;
- Reconfiguration: reconfigures the system at the runtime;
- QoS Management: encapsulates the strategies for QoS Management at the MW layer, interacting with the Resource Broker and the Monitor introduced above;
- Nomadic movement: realizes the application handoff for nomadic users;
- Roaming movement: realizes the application handoff for roaming users.
