FLEXible Middleware And Transports (FLEXMAT)

In particular, the QoS mechanisms of network transport protocols provide certain QoS properties for pub/sub DRE systems, e.g., reliability, latency, jitter. However, transport protocols traditionally have been evaluated apart from pub/sub DRE QoS concerns while pub/sub middleware leverage traditionally a single protocol or a handful of select protocols. Within this context, the following challenges present themselves: (1) the trade-offs of protocols in various environments are not highlighted and (2) the impact of protocol properties and multiple pub/sub QoS concerns are not known.

To address these challenges we have developed FLEXible Middleware And Transports (FLEXMAT). FLEXMAT integrates and enhances QoS-enabled pub/sub middleware with a flexible transport protocol framework. FLEXMAT also provides composite QoS metrics and empirical evaluations to highlight the QoS properties that different transport protocols present for a given operating environment. In particular, FLEXMAT includes the Adaptive Network Transport (ANT) framework, the (Data Distribution Service) (DDS), and the DDS QoS Modeling Language (DQML). DDS is a robust publish and subscribe (pub/sub) API standardized by the Object Management Group (OMG). DDS also provides the richest set of fine-grained QoS policy control provided by any pub/sub middleware standard. We have integrated and enhanced the OpenDDS open source DDS implementation with ANT and are currently focusing on the OpenSplice implementation for integration and enhancement due to its open source and extensive commercial grade support of the DDS specification. ANT is a transport protocol framework that supports composable modules with particular properties (e.g., acknowledgment-based reliability, negative acknowledgment based reliability, forward error correction, lateral error correction, XOR data encoding, Reed-Solomon data encoding). The ANT modules include:

• IPMulticastModule - for sending and receiving multicast packets
• MuxModule - for (de)multiplexing packets at the end host
• SequencerModule - for inserting sequence numbers into packet headers
• PrinterModule - for printing out packets sent and received
• AckModule - for positive acknowledgment reliability
• NakModule - for negative acknowledgment reliability
• GroupMembershipModule - for managing group membership
• FaultDetectionModule - for detecting when members leave groups

1. Joseph W. Hoffert, Douglas Schmidt, Aniruddha Gokhale, "Evaluating Transport Protocols for Real-time Event Stream Processing Middleware and Applications", The 11th International Symposium on Distributed Objects, Middleware, and Applications (DOA '09), Algarve, Portugal, November 2009

2. Joseph W. Hoffert and Douglas Schmidt, "FLEXible Middleware And Transports (FLEXMAT) for Real-time Event Stream Processing (RT-ESP) Applications", Workshop on Distributed Object Computing for Real-time and Embedded Systems (OMG RTWS '09), Washington, D.C., USA, July 13-15, 2009.

3. Joe Hoffert, Mahesh Balakrishnan, Douglas Schmidt, Ken Birman, "Supporting Large-scale Continuous Stream Datacenters via Pub/Sub Middleware and Adaptive Transport Protocols " The 2nd Workshop on Large-Scale Distributed Systems and Middleware (LADIS 2008), Yorktown, New York, USA, September 15-17, 2008.

4. Mahesh Balakrishnan, Joe Hoffert, Ken Birman, Douglas Schmidt, "Rethinking Reliable Transport for the Datacenter " The 2nd Workshop on Large-Scale Distributed Systems and Middleware (LADIS 2008), Yorktown, New York, USA, September 15-17, 2008.

5. Joe Hoffert, Mahesh Balakrishnan, Doug Schmidt, Ken Birman, "Supporting Scalability and Adaptability via ADAptive Middleware And Network Transports (ADAMANT)", Workshop on Distributed Object Computing for Real-time and Embedded Systems (OMG RTWS '08), Washington, D.C., USA, July 14-16, 2008.