Pragmatic General Multicast (PGM) is a reliable multicast transport protocol for applications that require ordered or unordered, duplicate-free, multicast data delivery from multiple sources to multiple receivers.

This paper presents the Reliable Multicast Protocol (RMP). RMP provides a totally ordered, reliable, atomic multicast service on top of an unreliable multicast datagram service such as IP Multicasting.RMP is fully and symmetrically distributed so that no site bears an undue portion of the communication load. RMP provides a wide range of guarantees.from unreliable delivery to totally ordered delivery, to K-resilient`majority resilient, and totally resilient atomic delivery.These QoS guarantees are selectable on a per packet basis. RMP provides many communication options, including virtual synchrony, a publisher/subscriber model of message delivery, a client/server model of delivery, an implicit naming service, mutually exclusive handlers for messages, and mutually exclusive locks.It has commonly been held that a large performance penalty must be paid in order to implement total ordeting--RMP discounts this. On SparcStationl0's on a 1250 KB/sec Etheruet, RMP provides totally ordered packet delivery to one destination at 842 KB/sec throughput and with 3.1 ms packet latency.The performance stays roughly constant independent of the number of destinations.For two or more destinations on a LAN. RMP provides higher throughput than any protocol that does not use mulficast or broadcast.

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This study examines Heifer International's alternative break and its impact on dietary and sustainable food system change for participants. The program teaches college participants about ending poverty and hunger while caring for the earth through incorporating sustainable practices into daily life. Although increases in local/organic foods were observed, there were no significant changes in dietary quality. Significant increases in local/organic food consumption for individuals who consumed less than 50% of their calories from sustainable foods at baseline were observed, based upon paired t-tests (P < .05). Dietary changes varied in significance based upon previous sustainable food consumption exposure and habits.

This paper describes the process of implementing a complex communications protocol that provides reliable delivery of data in multicast-capable, packet-switching telecommunication networks.The protocol, called the Reliable Multicasting Protocol (RMP), was developed incrementally using a combination of formal and informal techniques in an attempt to ensure the correctness of its implementation. Our development process involved three concurrent activities: (1) the initial construction and incremental enhancement of a formal state model of the protocol machine; (2) the initial coding and incremental enhancement of the implementation; and (3) model-based testing of iterative implementations of the protocol. These activities were carried out by two separate teams: a design team and a V&V team. The design team built the first version of RMP with limited functionality to handle only nominal requirements of data delivery. In a series of iterative steps, the design team added new functionality to the implementation while the V&V team kept the state model in fidelity with the implementation. This was done by generating test cases based on suspected errant or offnominal behaviors predicted by the current model. If the execution of a test was different between the model and implementation, then the differences helped identify inconsistencies between the model and implementation. The dialogue between both teams drove the co-evolution of the model and implementation. Testing served as the vehicle for keeping the model and implementation in fidelity with each other. This paper describes (1) our experiences in developing our process model; and (2) three example problems found during the development of RMP. This work is supported by NASA Cooperative Agreement NCCW-0040 under supervision of the NASA Independent Software Verification and Validation (IV&V) Facility, Fairmont, WV.Permission to make digltal/hard copies of all or part of this material for pereoaal or classroom use is granted without fee p.rovi.dad that the copies are not made or distributed for profit or commerctal aavantagc, mc COlbyright notice, the title ofthc publication and its date appear, and noticc is given that copyright is by permission of the ACM, Inc. To copy othc .rwise, to repubfish, to post on servers or to redistribute to lists, requires specittc permission and/or fee. ISSTA '96,