Subject: [core] #15: Consolidate maximum sizes (encodings, options table, maximum datagram)

From: "core issue tracker" <[email-masked]>
Date: Wed, 16 Jun 2010 10:32:58 -0000

#15: Consolidate maximum sizes (encodings, options table, maximum datagram)
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 Reporter:  hartke@…            |       Owner:            
     Type:  defect              |      Status:  new       
 Priority:  minor               |   Milestone:  milestone1
Component:  coap                |     Version:  1.0       
 Severity:  Active WG Document  |    Keywords:            
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 According to the option encoding, the maximum length for an option value
 is 1023 bytes ("octets").  According to table 2, a URI can be up to 32768
 [sic] bytes.  This is not necessarily a contradiction, as clearly the
 maximum length is the minimum of the two maxima.  But then, section 4 says
 "When bound to UDP the entire message MUST fit within a single datagram of
 length 1024 octets.", which is another restriction.  The latter
 restriction also makes it impossible to send a payload of 1024 bytes even
 if enough space would be available in the 1280 byte IPv6 MTU.

 We need to agree what would be good upper bounds.

-- 
Ticket URL: <http://trac.tools.ietf.org/wg/core/trac/ticket/15>
core <http://tools.ietf.org/core/>

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From: "core issue tracker" <[email-masked]>
Date: Wed, 30 Jun 2010 10:39:04 -0000

Priority:  minor               |   Milestone:     

Comment(by zach@…):

 - The URI and option length discrepency is being fixed already.

 - Regarding the maximum message size, I propose text like this which is
 similar to that used by other UDP based protocols such as m-DNS:

 "The resulting datagram carrying a CoAP message MUST fit within a single
 MTU of that phsical interface, which is typically 1500 bytes for an
 Ethernet interface and 1280 bytes for a 6LoWPAN interface."

-- 
Ticket URL: <http://trac.tools.ietf.org/wg/core/trac/ticket/15#comment:2>
core <http://tools.ietf.org/core/>