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RE: [bacnet-ip-wg] Internet Protocol Version 6 familiarization

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  • Roland Laird
    Jim and Coleman, The trick in IPv6 is that each adapter has multiple addresses for each scope of addressing. The way I see it, RL-003-10 will work on a B/IPv6
    Message 1 of 7 , Jan 8, 2010
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      Jim and Coleman,

       

      The trick in IPv6 is that each adapter has multiple addresses for each scope of addressing. The way I see it, RL-003-10 will work on a B/IPv6 subnet in the same way as IPv4 works simply by using a local scope multicast. Likewise on a wide-area corporate Intranet organization-local multicast can be used and all will work without the BBMD concept. The BBMD concept is only needed (as currently defined in RL-003) to allow for foreign devices form outside the organization to join the network.

       

      On the reduction of broadcasts issue, I am mostly concerned about it over wide-area networks where routers block them. This is where we need the BBMD to distribute the broadcasts using Forwarded-NPDUs. Although broadcasts on a local subnet cause burdens for every host, I don’t think it is a big problem. Using multicasts in IPv6 will make that problem go away. I would like to see Forwarded-NPDUs go away as well, because with Dynamic hosting the device does not know the “address with which the original node is accessed”.

       

      For reducing broadcasts over wide-area networks I see three separate problems that apply equally to IPv4 and IPv6:

      1.       The Forwarded-NPDUs of APDU broadcasts (like those identified by Jim below)

      -          I think these can be eliminated by not having a BACnet Network span subnets. The ‘special’ BACnet Network joining multiple subnets would not have any devices and would not receive any broadcasts. Routers (that have learned the inter-network) would send directed broadcasts to other routers. Every message across subnet boundaries would be directed.

       

      2.       How does the network layer learn the addresses of remote networks?

      -          Should  support use of domain names

      -          How is this configured?

      -          IP data link does physical binding

      -          IPv6 will then go through VMAC

      -          Some body smarter than me needs to figure this out

       

      3.       How do foreign devices join the internetwork?

       

      Roland

       

       

      From: bacnet-ip-wg@yahoogroups.com [mailto:bacnet-ip-wg@yahoogroups.com] On Behalf Of Coleman Brumley
      Sent: January 8, 2010 11:17 AM
      To: bacnet-ip-wg@yahoogroups.com
      Subject: RE: [bacnet-ip-wg] Internet Protocol Version 6 familiarization

       

       

      Jim,

       

      > My feeling is that trying to come up with a comprehensive solution to BACnet’s broadcast problem might be too much to tackle within the context of your IPv6 proposal.  The working group > should decide whether that is in scope or out of scope.

      Agreed.  And there's no way we'd be able to tackle something of this magnitude in Orlando, anyway.  I in no way am trying to hold up the current proposal.  As Roland points out, it's important to get it in front of a wider audience to get some feedback.  A "ship early" and "increment often" kind of approach. 

       

      However, the problem that I see with not addressing broadcasts early in this whole endeavor is that BACnet broadcasts as they are currently defined may cease to work in IPv6.  To me, it's not "how broadcasts can be reduced" but rather how broadcasts are used in IPv6 at all. 

       

      My hope was that we could discuss this in Orlando and come with a wish list of how to proceed with broadcasts in IPv6.  A list of what is "above the line" and "below the line" for initial IPv6 support in BACnet. 

       

      Coleman

       

      From: bacnet-ip-wg@yahoogroups.com [mailto:bacnet-ip-wg@yahoogroups.com] On Behalf Of James F. Butler
      Sent: Friday, January 08, 2010 2:04 PM
      To: bacnet-ip-wg@yahoogroups.com
      Subject: RE: [bacnet-ip-wg] Internet Protocol Version 6 familiarization

       

       

      Hi Coleman,

       

      We (Cimetrics) have been thinking about how broadcasts could be reduced in BACnet IT.  Consider that the following BACnet application-layer services use (or may use) broadcasts:

       

      Who Is & I Am

      Who Has & I Have

      Unconfirmed COV Notification

      Unconfirmed Event Notification

      Time Synchronization & UTC Time Synchronization

      Unconfirmed Private Transfer

      Unconfirmed Text Message

       

      If we want to maintain the functionality provided by the broadcast forms of all of these services, then we need to develop alternatives to broadcasts for each of them.  The use of multicast is one option that should be seriously considered, but simply replacing broadcasts with multicasts does not address the fundamental scalability problem.

       

      My feeling is that trying to come up with a comprehensive solution to BACnet’s broadcast problem might be too much to tackle within the context of your IPv6 proposal.  The working group should decide whether that is in scope or out of scope.

       

      - Jim Butler

       

       

       

       

       


      From: bacnet-ip-wg@yahoogroups.com [mailto:bacnet-ip-wg@yahoogroups.com] On Behalf Of Coleman Brumley
      Sent: Monday, January 04, 2010 5:07 PM
      To: bacnet-ip-wg@yahoogroups.com
      Subject: RE: [bacnet-ip-wg] Internet Protocol Version 6 familiarization

       






      Hi Jim,

       

      I had hoped to add support for the different broadcast types (anycast, multicast, etc.) in this revision of the document and really examine how the use of broadcasting will be affected by the use IPv6. 

       

      However, it doesn't look like we'll have time (for this revision of the proposal) to accomplish that or address any wish list items due to the requirement of getting this out to public review quickly.  See my email on 1-Dec-2009 titled "RE: IPv6 presents an opportunity for elimination of broadcast". 

       

      Do we honestly think we can reach consensus on something as big as broadcasts in 2 hours?

       

      I certainly understand the need to get this out to public review for the Smart Grid work -- and I don't disagree with it.  However, I think we're missing the boat on some other important opportunities here. 

       

      Coleman

       

      From: bacnet-ip-wg@yahoogroups.com [mailto:bacnet-ip-wg@yahoogroups.com] On Behalf Of James F. Butler
      Sent: Monday, January 04, 2010 12:33 PM
      To: bacnet-ip-wg@yahoogroups.com
      Subject: RE: [bacnet-ip-wg] Internet Protocol Version 6 familiarization

       

       

      Hi Roland,

      Will we be discussing an IPv6 proposal in Orlando? If so, I would like
      to see it at least a few days prior to the meeting.

      Thanks,

      - Jim Butler

      -----Original Message-----
      From: bacnet-ip-wg@yahoogroups.com [mailto:bacnet-ip-wg@yahoogroups.com]
      On Behalf Of rolandlus
      Sent: Wednesday, November 25, 2009 12:19 PM
      To: bacnet-ip-wg@yahoogroups.com
      Subject: [bacnet-ip-wg] Internet Protocol Version 6 familiarization

      This is a list of the main IPv6 RFC documents that describe the core
      components of IPv6. It was requested that the IP-WG familiarize
      themselves with IPv6 so that we are equipped to review the next
      proposal. Coleman Brumbley will be providing an update to the current
      RL-003-10. RL-003-10 is in the Files section of this Yahoo Group.

      http://www.ietf.org/rfc.html

      RFC 2460: Internet Protocol, Version 6 (IPv6)
      RFC 4294 : IPv6 Node Requirements
      RFC 4291: IP Version 6 Addressing Architecture
      RFC 4193: Unique Local IPv6 Unicast Addresses
      RFC 3306: Unicast-Prefix-based IPv6 Multicast Addresses
      RFC 3307: Allocation Guidelines for IPv6 Multicast Addresses

      We will be allocated at least two hours in Orlando critically review the
      BACnet/IPv6 proposal. As the Smart Grid is looking to IPv6, it is
      important that we move this proposal out to public review ASAP. Please
      take time before Orlando to study the RFCs and RL-003-10.

      Thanks Roland

       

       





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