A Transport Framework for Distributed Brokering Systems Shrideep Pallickara, Geoffrey Fox, John Yin, Gurhan Gunduz, Hongbin Liu, Ahmet Uyar, Mustafa Varank spallick, Community Grid Computing Laboratory, Pervasive Technology Labs Indiana University.

June 25th PDPTA Talk Outline Motivation Issues that need to be addressed Overview of NaradaBrokering Discussion of elements in the framework Experimental results Conclusions

June 25th PDPTA Motivation Services need to interact with entities with disparate networking capabilities –In networking environments. Different transports suitable for different tasks TCP for reliable, Multicast in high concentrations. Services work on higher level abstraction of links Manage communications to achieve highest possible performance and reliability.

June 25th PDPTA Issues that need to be addressed Framework Design –Abstract communication requirements of service layers. –General enough, no details pertaining to specific transports. –Should be able to incorporate support for new transports easily. Ability to deploy special links for specific applications e.g. UDP for audio/video traffic. Performance Monitoring Migration Support Negotiate best transports –Eg. Multicast in clusters instead of point-to-point UDP.

June 25th PDPTA NaradaBrokering: Features Based on a network of cooperating broker nodes –Cluster based architecture allows system to scale. Originally designed as a distributed event service. Now has four major core functions –Message transport (based on performance) in multi-link fashion –General publish-subscribe including JMS, JXTA and Gnutella (started) –Support for RTP-based audio/video conferencing. –Federation of multiple instances (just starting) of Grid services

June 25th PDPTA Why such a Framework for NB An event traversing over multiple hops could traverse multiple protocols. Protocol layers do not need to deal with transport details –Deals with the abstraction notion of connection link. –Delegate determination of failures to transport layer. Broker network should be able to reorganize connections to disseminate data optimally –Transport interfaces need to provide information to manage this.

June 25th PDPTA Link Abstracts communications between 2 end points. –Implementations of Link interface can incorporate transport specific handshaking protocols. Failure Detection –Check status of underlying protocols and report failures. Garbage collection of alternate link s –Certain link s may be short-lived. Transport protocol migrations Security Information

June 25th PDPTA Link Factory Manages Links of a specific communications type. Facilitate creation of inbound and outbound communication links. Manage migration of communications from a different underlying communication protocol. Enable or disable measurement of performance monitoring over a link or its entire set of managed links.

June 25th PDPTA Administrative Links Used to exchange information between two nodes regarding the available communications. –Depending on firewall, proxy and NAT boundaries communications will be over a small set of protocols. This information is then used to negotiate best possible transport. Communication over the Administrative Link should be HTTP based.

June 25th PDPTA Transport Handler Manages all registered LinkFactory s Maintains reference to Monitoring Service Serves as an intermediary between the transport and protocol layers. Individual link s report availability of data streams to Transport Handler. Manage creation of alternate link s –Special Link s deployed to handle communication requirements of specific applications.

June 25th PDPTA Performance Monitoring Every link measures and exposes a set of metrics –Average delays, jitters, loss rates, throughput. Individual link s can disable measurements for individual or the entire set of metrics. Measurement intervals can also be varied Monitoring Service, returns measured metrics to Performance Aggregator.

June 25th PDPTA Performance Monitoring Snapshot

June 25th PDPTA NaradaBrokering Communications

June 25th PDPTA Other advantages Possible to implement transport interfaces to deal with legacy clients. –For example we implemented RTP based interfaces to deal with legacy clients. Can also be used to deal with device specific transcoding and transformations.

June 25th PDPTA Pentium-3, 1GHz, 256 MB RAM 100 Mbps LAN JRE 1.3 Linux

June 25th PDPTA

June 25th PDPTA

June 25th PDPTA Conclusions and Future work We presented a transport framework that is appropriate for distributed brokering systems. Some issues need to be investigated further –Specification of migration constraints. –Determine feasibility of constraint evaluations in real-time settings. –Inclusion of codec transformations in link interfaces.

June 25th PDPTA Related Works JXTA CORBA JMS NWS