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Re: [core] Request for clarification of NSTART and concurrent requests

Carsten Bormann <cabo@tzi.org> Tue, 16 August 2022 13:13 UTC

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From: Carsten Bormann <cabo@tzi.org>
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Date: Tue, 16 Aug 2022 15:13:17 +0200
Cc: Bryan Green <bryan@aetheros.com>, core@ietf.org
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To: Achim Kraus <achimkraus@gmx.net>
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Subject: Re: [core] Request for clarification of NSTART and concurrent requests
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Thanks for the quick reply, Achim!

Adding chapter and verse:

> there are two options:
> 
> - 4.29 "Too many requests"

This is described in RFC 8516, which compares 4.29 to 5.03 by stating "However, the 4.29
   code indicates that the too-frequent requests from the requesting
   client are the reason for the overload.”

So, the error is really client-induced and therefore has a 4.xx code.

> - 5.03 "Service unavailable"

This is described in Section 5.9.3.4 of RFC 7252:
5.03 Service Unavailable

> both with a proper value for "Max. Age." (option 14).

Which also explains the use of Max-Age, but RFC 8516 is a bit less terse about the use of that option (and the possible surprise by its default value).

Grüße, Carsten

> 
> best regards
> Achim
> 
> Am 15.08.22 um 22:40 schrieb Bryan Green:
>> What would be the appropriate response to a CON request from a
>> constrained coap server that had reached its limit of concurrent
>> requests from a single client?
>> For example if a server was only capable of handling one CON request per
>> client at a time, and a CON request was received while the prior request
>> was still being processed, should the server silently ignore the packet,
>> or is there an appropriate response code to inform the client of the
>> need to wait?
>> 
>> 
>> On Mon, Aug 15, 2022 at 1:13 PM Bryan Green <bryan@aetheros.com
>> <mailto:bryan@aetheros.com>> wrote:
>> 
>>    Thank you very much for the response.  That answers my question.
>> 
>>    -Bryan
>> 
>> 
>>    On Mon, Aug 15, 2022 at 12:22 PM Carsten Bormann <cabo@tzi.org
>>    <mailto:cabo@tzi.org>> wrote:
>> 
>>        On 15. Aug 2022, at 21:19, Carsten Bormann <cabo@tzi.org
>>        <mailto:cabo@tzi.org>> wrote:
>>         >
>>         > heavily suggested
>> 
>>        heavily CONgested
>> 
>>        Sorry about that surprising auto-correct.
>> 
>>        Grüße, Carsten
>> 
>> 
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>> core@ietf.org
>> https://www.ietf.org/mailman/listinfo/core
> 
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