Re: [core] YANG notification within CoMI

Peter van der Stok <stokcons@bbhmail.nl> Tue, 12 June 2018 12:09 UTC

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Date: Tue, 12 Jun 2018 14:09:42 +0200
From: Peter van der Stok <stokcons@bbhmail.nl>
To: Michel Veillette <Michel.Veillette@trilliant.com>
Cc: consultancy@vanderstok.org, Andy Bierman <andy@yumaworks.com>, Alexander Pelov <a@ackl.io>, "Eric Voit (evoit)" <evoit@cisco.com>, Henk Birkholz <henk.birkholz@sit.fraunhofer.de>, yot@ietf.org, Core <core@ietf.org>
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Subject: Re: [core] YANG notification within CoMI
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I think Carsten and also Michael have started to discuss an approach to
the current implementation short comings and resilience additions.

Peter
Michel Veillette schreef op 2018-06-11 23:12:

> Hi Peter 
> 
> About " I recommend to maintain section 5.5, as is, in the CoMI draft and start looking at the other subjects separately."
> 
> The current 'observe' method might still be useful for some use cases which requires a temporary subscription. For example, this method can be used to temporarily subscribe to the syslog for debug purposes. This method can also be used to wait for the completion of a transaction initiated using the normal CoAP methods. 
> 
> To address the more common event stream use cases (i.e. a something equivalent to SNMP traps), it seem we need to introduce a new mechanism. 
> 
> About how to solution should be packaged (i.e. one of two drafts), we should probably wait for a better understanding of the direction we want to take. 
> 
> Regards, 
> 
> Michel 
> 
> FROM: Peter van der Stok [mailto:stokcons@bbhmail.nl] 
> SENT: Monday, June 11, 2018 3:20 AM
> TO: Michel Veillette <Michel.Veillette@trilliant.com>
> CC: Andy Bierman <andy@yumaworks.com>om>; Alexander Pelov <a@ackl.io>io>; Eric Voit (evoit) <evoit@cisco.com>om>; Henk Birkholz <henk.birkholz@sit.fraunhofer.de>de>; yot@ietf.org; Core <core@ietf.org>
> SUBJECT: Re: YANG notification within CoMI 
> 
> Hi Michel,
> 
> Thanks for the message.
> I think that load balancers, stable storage for messages, californium implementation restrictions are all separate subjects, and merit a solution independent of CoMI.
> 
> I recommend to maintain section 5.5, as is, in the comi draft and start looking at the other subjects separately.
> 
> Peter 
> 
> Michel Veillette schreef op 2018-06-08 20:17:
> 
>> Support the YANG notifications in the current CoMI draft (i.e https://www.ietf.org/id/draft-ietf-core-comi-03.txt [1]) 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
 

Links:
------
[1] https://www.ietf.org/id/draft-ietf-core-comi-03.txt