Subject: [core] #244: max-age vs. network latency and retransmissions

From: "core issue tracker" <[email-masked]>
Date: Fri, 28 Sep 2012 18:34:44 -0000

#244: max-age vs. network latency and retransmissions

 Cullen Jennings notes (msg03072ai):

 Section 5.7

 Last paragraph of section 5.7. I'm worried about slowly extending the life
 time of the cache by each step not taking into account the network
 latency. So if there is 2 condos of latency on the mesh network and device
 A passed something with a Max-Life to 10 seances to Cache B that later
 caches to cache B, it could end up living for multiple seconds longer than
 it should have.

 Also, Klaus Hartke notes (nits9c):

     Retransmission of a response can significantly extend the
     time the response takes to arrive at the client. Should the
     Max-Age of the response be reduced with each retransmission?
     (See also [msg03072ai])

 The somewhat lame text that has been added to the working version of
 coap-12 is:

         Considering potential network delays on the way from the
         origin server,
         a proxy SHOULD be conservative in the max-age values offered.

 However, we could also add text that recommends (or requires?) proxies to
 update max-age in their retransmissions.  We could also extend this
 recommendation/requirement to origin servers.

 Carsten's view:
 In many cases, this is a quality of implementation issue.
 But it does not hurt to point out the issue.
 So I added text in the definition of the option Max-Age that indicates
 that the value of Max-Age is current at the time of transmission.

-- 
-----------------------------+------------------------------------
 Reporter:  cabo@…           |      Owner:  draft-ietf-core-coap@…
     Type:  other technical  |     Status:  new
 Priority:  minor            |  Milestone:  post-WGLC-1
Component:  coap             |    Version:  coap-09
 Severity:  In WG Last Call  |   Keywords:
-----------------------------+------------------------------------

Ticket URL: <http://trac.tools.ietf.org/wg/core/trac/ticket/244>
core <http://tools.ietf.org/core/>