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Requirements for Internet Scale Event Notifications

This article discusses the minimum requirements for qualifying as an event notification service, the need for specialized services and inter-service communication, core requirements for notification delivery, authentication, compatibility with existing firewalls, selectivity, and more. It also delves into domain-specific requirements for printing, satellite services, financial services, and discusses other issues such as defining minimal requirements and notification ordering.

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Requirements for Internet Scale Event Notifications

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  1. Requirements for Internet Scale Event Notifications David Rosenblum UC Irvine Surendra Reddy Oracle

  2. Questions • What are the minimum requirements a technology must satisfy to qualify as an event notification service? • Does any kind of IPC qualify? • Can we define the event notification service for the Internet, or do we need several specialized services? • If the latter, then support for inter-service communication is needed

  3. Core Requirements (I) • A separate service, available anywhere on the Internet • A programmatic interface • Notification subscription • Content-based subscription • Asynchronous notification delivery • Reliable notification delivery

  4. Core Requirements (II) • Authenticated notifications • Decentralized/networked architecture • Anonymity of publishers & subscribers • Compatible with existing firewalls • Selectivity • All interested parties receive notifications • Only interested parties receive notifications

  5. Core Requirements:Discussion • Protocol definition • (invisible) standard protocols vs. (visible) proprietary APIs • Decoupling of publishers & subscribers • But not necessarily anonymity • Subscriber for notification can be different from recipient

  6. Core Requirements:Discussion • Persistence of notifications • Impact of Internet scale on persistence • Built into service? • Provided by service users through callbacks? • Standard terminology • Discoverability of quality of service • Extensibility of service features

  7. Domain-Specific Requirements:Internet Printing • Multiple “channels” or classes of notifications • Grouping/patterns of events (“job done” vs. “page 3 done”) • Support for “large” numbers of clients • Multiple notification methods (email, programmatic, log files, etc.) • Eliminate redundancy—treat print requests as subscriptions

  8. Domain-Specific Requirements:Satellite Services • 108-109 events per day • Wide-area notification, at least continental US • Timely delivery (on the order of seconds), but not necessarily reliable • Aggregation of notifications

  9. Domain-Specific Requirements:Financial Services • 1000 notifications to 5-10,000 workstations per second • Historical notification storage and matching • Reliable multicast

  10. Domain-Specific Requirements:Discussion • Single service vs. single protocol w/multiple infrastructures vs. multiple protocols • Variation in (cost of satisfying) different quality of service requirements may result in multiple services • All providers agree on base level of QoS but can advertise additional capabilities

  11. Domain-Specific Requirements:Discussion • Incompatibility between QoS requirements may result in multiple services • Example: notification delivery semantics • Idempotence vs. at-least-once vs. at-most-once vs. exactly-once

  12. Other Issues:Discussion • Defining “minimal requirements” may result in multiple, domain-specific services • Notification schema • Message format, minimal information, fixed or variable media types, … • Reconciling users’ and providers’ view of the schema • Notification ordering

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