Subject: [core] Block-wise transfer late negotiation and unrecognized critical options

From: "Valerio Di Gregorio" <[email-masked]>
Date: Thu, 04 Oct 2012 10:34:56 +0200

Dear all,
I want to share with you my problem. Intecs CoAP implementation supports 
resource discovery but it does not support the block-wise transfer. In a 
late negotiation scenario (i.e. GET 
coap://vs0.inf.ethz.ch:5683/.well-known/core) Intecs client fails 
receiving a Block2 (#17) option from the server. It is OK because option 
17 is an unrecognised critical option for the client.

The question is: can the server use the block-wise transfer when it is 
not strictly needed?

In my opinion if the request does not contain a Block2 option, the 
server can not assume block-wise transfer supported by the client and 
avoid it. By the way in some cases (i.e. payload too long, not enough 
resources, security reasons, etc.) a late negotiation attempt is still 
better than an error code. From my point of view late negotiation should 
be a "last resort solution".

BR,
Valerio

-- 

Valerio Di Gregorio
Automotive and Telecommunication Division
Software Engineer

INTECS Informatica e Tecnologia del Software S.p.A.
Via Umberto Forti, 5
Polo di attività di Montacchiello
56121 Ospedaletto, Pisa
Italy

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