Requirements for Internet Scale Event Notifications

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

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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

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Core RequirementsDiscussion

• 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

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Core RequirementsDiscussion

• 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

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Domain-Specific RequirementsInternet 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 redundancytreat print requests as
  subscriptions

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Domain-Specific RequirementsSatellite 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

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Domain-Specific RequirementsFinancial Services

• 1000 notifications to 5-10,000 workstations per
  second
• Historical notification storage and matching
• Reliable multicast

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Domain-Specific RequirementsDiscussion

• 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

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Domain-Specific RequirementsDiscussion

• 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

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Other IssuesDiscussion

• 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