[core] YANG notification within CoMI

Michel Veillette <Michel.Veillette@trilliant.com> Fri, 08 June 2018 18:17 UTC

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From: Michel Veillette <Michel.Veillette@trilliant.com>
To: Peter van der Stok <stokcons@bbhmail.nl>, Andy Bierman <andy@yumaworks.com>, Alexander Pelov <a@ackl.io>, "Eric Voit (evoit)" <evoit@cisco.com>, Henk Birkholz <henk.birkholz@sit.fraunhofer.de>
CC: "yot@ietf.org" <yot@ietf.org>, Core <core@ietf.org>
Thread-Topic: YANG notification within CoMI
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Date: Fri, 8 Jun 2018 18:17:19 +0000
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Subject: [core] YANG notification within CoMI
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Support the YANG notifications in the current CoMI draft (i.e https://www.ietf.org/id/draft-ietf-core-comi-03.txt) is based on the observe option as defined by RFC7641.



This solution has the following issues which make it not practical for the targeted use case.



1) This approach in incompatible with load balancers, notifications are directly returned to the specific server within the cluster which have initiated the observe request.

2) Typical CoAP implementation (e.g. Californium) doesn't support the persistence of the observe context. These contexts can't be recovered after a server restart and can't be shared between servers.

3) Registrations to event streams are not resilient, they can terminate unexpectedly upon transmission error or reception of a Reset message.



I recommend to delete draft-ietf-core-comi section 5.5 and start a specific effort on this topic.

Alignment with the [I-D.ietf-netconf-yang-push] also need to be considered.

Those interested to this topic, please send me a email so I can schedule conference calls or a face to face meeting during the next IETF.



The following diagram shows a typical deployment scenario.



  +---------+  +---------+       +---------+

  | CoMI    |  | CoMI    |  ...  | CoMI    |

  | server  |  | server  |       | server  |

  +---------+  +---------+       +---------+

       |            |                 |

       |            |                 |

       +----------+-+-----------------+

                  |

                  |

   +---------------------------------+

   | CoMI         |                  |

   | client       |                  |

   |         +----------+            |

   |         | Load     |            |

   |         | Balancer |            |

   |         +----------+            |

   |              |                  |

   |        +-----+---------+        |

   |        |               |        |

   |   +---------+     +---------+   |

   |   | Server  | ... | Server  |   |

   |   +---------+     +---------+   |

   |        |               |        |

   |        +-------+-------+        |

   |                |                |

   |           +----------+          |

   |           | Database |          |

   |           +----------+          |

        |                                 |

   +---------------------------------+

Regards,
Michel