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Re: [bacnet-mstpwg] Reactivate 135-2008ad-8 Increase Segmentation Window Size for MS/TP

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  • Clifford.H.Copass@jci.com
    I think the main difference is the 135-2008ad, part 8 proposal would work with existing routers and has no known conflicts with existing devices that would not
    Message 1 of 3 , Jun 16, 2011
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      I think the main difference is the 135-2008ad, part 8 proposal would work with existing routers and has no known conflicts with existing devices that would not understand the larger frame sizes.

      Cliff Copass
      Johnson Controls, Inc.



      From:Kerry Lynn <kerlyn2001@...>
      To:bacnet-mstpwg@yahoogroups.com
      Date:06/16/2011 11:05 AM
      Subject:Re: [bacnet-mstpwg] Reactivate 135-2008ad-8 Increase Segmentation Window Size for MS/TP







      Cliff,


      Is there a need in practice to send datagrams larger than 1497 octets over
      MS/TP?  I ask because there *is* a proposal in the pipeline for sending
      large frames over MS/TP.

      -K-

      On Thu, Jun 16, 2011 at 11:33 AM, cliffcopass <Clifford.H.Copass@...> wrote:
       
      After the first public review of 135-2008ad, part 8 was removed due to a single comment suggesting that an alternate mechanism could be used to accomplish the same result (send segments without expecting a reply).

      After some thought, I am not at all convinced that this alternate approach would be without backward compatibility and inter-operational issues when communicating with some devices (depending on the implementation). It also complicates sending aborts, etc. back to the message originator.

      The original approach is fully backward compatible, does not change the higher level protocol (i.e. how segments are sent) and clears up some of the protocol stack issues in the standard.

      I would like to consider reactivating this proposal given that no one has come forward with a better alternative that is unlikely to cause communication problems in some situations.

      Cliff Copass






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