Instant Message Delivery Notification (IMDN) for Presence and Instant Messaging (CPIM) Messages

1
Instant Message Delivery Notification (IMDN) for
Presence and Instant Messaging (CPIM) Messages

• draft-burger-simple-imdn-01
• Eric Burger

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IMDN

• Transport Notifications Handled by OK (p2p) and
  REPORT (MSRP)
• Return Receipt
• User Notifications Needed
• Recipient UAS Received Message, But Did User
  Actually See/Hear/Feel Message?
• Read Receipt, or other dispositions

3
Internet Mail Approach Message Delivery
Notification (MDN)

• After Message Delivered, i.e., Available for
  Presentation to User
• Not a Non-Repudiation Service
• A Regular Message Body
• Uses Message Transport and Delivery Mechanisms
• User Readable
• Machine Readable

4
Abstract Flow

• Sender Marks Message for Reporting
• Message Becomes Available to the Recipient
• Possibly Expanded Through Recursive List
  Expansion
• Recipient Disposes of the Message
• Read, Delete, Other
• Recipient UA Sends Message Disposition
  Notification to Sender

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B2BUA

• Often, Recipient is Not Human
• Common B2BUA Situations for CPIM
• Gateway to foreign IM Network
• List Expansion
• User Interpretation of Read Report Might Not
  Match Protocol Interpretation
• Gateway may read message to forward it
• User expects report to relate to final destination

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What Dispositions?

• Asking for a Failed Delivery Report Does Not Make
  Sense
• Delivery failure report only happens on happy
  path UAS generates report.
• Most likely to have no report for failure
• UAS failure, UAS deciding to not send IMDN,
  network failure all look identical, and more
  likely than success being the absence of a
  failure message
• Thus One and Only One Reporting Request

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Harmony

• IMDN and im-report Have Similar Flavor
• From im-report
• XML Data Format
• Absence of Header / Empty Value Means Explicit
  Report Suppression
• B2BUA Drives Reporting
• From IMDN (High Level)
• Reduce State Request to Read
• List Expansion / Gateway Mechanism
• User Privacy Considerations
• Require Processing Allows UAS to Explicitly
  Reject Request
• End-to-End Report Integrity

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Open Issue 1 B2BUA Reporting

• Proposal 1 Punt. Delivery is to B2BUA. IMDN
  indicates processed
• Protocol Purity
• Proposal 2 Always Assume User Wants Final
  Recipient Report
• Matches Most User Expectations
• Proposal 3 Allow User to Indicate Which They
  Want
• Precisely Matches User Expectations
• No Burden on UAS
• Pretty Easy for UAC
• IMDN Today Uses Proposal 3

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Open Issue 1a Consolidated Reporting

• For List Expansion, User Wants Either
• A Single Report With All Deliveries
• Delivery Reports for Each Recipient
• IMDN Today Is Proposal 2
• Leaning Towards 1
• (im-report mechanism doesnt work)

• Proposal 1 Per-Recipient Reporting
• Easy Implementation at UAS, B2BUA
• Flood Potential at UAC
• Security Privacy Issues
• Proposal 2 B2BUA Consolidates Reports
• B2BUA Collects IMDNs from Recipients
• How Long to Wait for IMDNs?
• What About Late IMDNs?

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Open Issue 2 Notification-To

• Simplification for B2BUA State Storage
• Endpoints Report Directly to Sender
• Method Used by MDN
• BUT MDN is SPAM-Friendly
• Would Require Sender Authentication and UAS Trust
  of B2BUA (transitive via sips?)
• Or, Use im-reports Mechanism of B2BUA Relaying
  Responses
• Requires Infinite State Storage at B2BUA
• Proposal Use im-reports Mechanism With Local
  Policy Timeout Plus No More Reports Coming
  Protocol Action

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Open Issue 3 Human Reports

• MDN is multipart/report
• One part is human readable what happened to your
  message
• Another part is machine readable error codes,
  etc.
• Do we want something users can read?
• Grandma does not understand XML or headers

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Open Issue 4Transport Encoding

• XML Is Cool. Wow.
• Headers Work. Boring.
• Headers Easy to Extend and Parse. Wow.
• XML Parser Validates Tags. Cool.
• All CPIM Processors MUST Parse and Process
  Headers. Excellent.
• Some CPIM-Transported Messages are In XML. Neat.
• Headers Have Namespaces, Too (CPIM Model)
• Proposal Use Headers, not XML (IMDN-00)

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Work to Do

• Correct Errata
• Need to do examples
• Example is really schema
• Security Privacy From Notification-To Present
• Forgot to specify report type (over deletion from
  IMDN-00)

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Other Slides

• Not for Presentation, Unless Needed

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Details IMDN vs. im-report

• Explanation (and use case) for globally unique
  Message-ID
• Remove Failure Report Request Only Meaningful
  Report Request is read
• No confusion between REPORT and IMDN
• Content-Disposition
• IMDNs Can Have Message-IDs
• Never get 485, so no similar mechanism do have
  other states, though (processed, expanded,
  denied)
• IMDN Provides Privacy Considerations
• B2BUA Disposition States adds processed,
  expanded, denied
• End-to-End Integrity of Reports
• Reports Get Nested, so S/MIME Can Work
• NO MULTIPLE REPORTS FOR SINGLE TRANSACTION

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List Expansion in im-report

• Cant work as specified
• Recipient-uri needs to explicitly be end target
  URI
• Some might be ltreadgt, others might be something
  else
• No possibility for end-to-end integrity all from
  B2BUA