DDSI-RTPS 2.0 NO IDEA Avatar
  1. OMG Issue

DDSIRTP2 — Clarify interoperability requirement 8.4.2.3.4

  • Key: DDSIRTP2-8
  • Legacy Issue Number: 11036
  • Status: closed  
  • Source: Real-Time Innovations ( Mr. Kenneth Brophy)
  • Summary:

    Source:
    Real-Time Innovations, Inc. (Ken Brophy, ken@rti.com)
    Summary:
    Requirement 8.4.2.3.4 currently states "Readers can only send an ACKNACK Message in response to a HEARTBEAT message." This implies a reader may not poll for samples by unilaterally NACKing. This is true in general: the frequency and bandwidth of NACKs and associated repair messages is well maintained if controlled only by the writer. However, in the case when a Reader first finds out about a remote writer, before it receives any heartbeats, it may optionally send an ACKNACK to notify the writer. This can expedite communications between the new writer/reader pair, as the arrival time of the first heartbeat may be indeterminate.

    The rationale of writer-only control of NACK and associated repair messages should be incThis optimization should be noted within an implementation note.

    Resolution:
    Clarify requirement 8.4.2.3.4 to include the special case of a Reader first discovering a Writer.
    Revised Text:
    ยท Change the text of Section 8.4.2.3.4 to:

    In steady state, an ACKNACK Message can only be sent as a response to a HEARTBEAT Message from a Writer. ACKNACK Messages can be sent from a Reader when it first discovers a Writer as an optimization. Writers are not required to respond to these pre-emptive ACKNACK Messages.

  • Reported: DDSI-RTPS 2.0b1 — Wed, 23 May 2007 04:00 GMT
  • Disposition: Resolved — DDSI-RTPS 2.0
  • Disposition Summary:

    see above

  • Updated: Fri, 6 Mar 2015 20:58 GMT