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169RE: [bacnet-ip-wg] Asked an IT person about IPv6 multicast

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  • Clifford.H.Copass@jci.com
    Aug 22 9:46 AM

      Actually I am a bit confused also, but I wanted to pass along what was sent to me.

      I think the key issues are:
      1 - IT departments only implement what they have to.  Don't expect anything special for BACnet.
      2 - Expect mixed IPv4 and IPv6 networks, especially where expensive IPv4 switches would have to be replaced to "do it right".

      Cliff Copass

      From:"Coleman Brumley" <bacnet_cb@...>
      Date:08/22/2011 09:50 AM
      Subject:RE: [bacnet-ip-wg] Asked an IT person about IPv6 multicast



      Thank you for doing this research.  


      It seems that the answer, though, didn't really address the multicast issue.  Perhaps I'm missing something?  IPv6 requires all routers to support link-local multicast which is what is used primarily by B/IPv6.  In other cases, organization scope multicast is used.  In the case where multicast is disabled, then a  B/IPv6 BBMD is required.  


      I'm confused by the "worst case scenario" that is listed:


      "Therefore consider the worst case scenario whereby the entire IT managed infrastructure only supports IPv4 routers, DNS (A records only), and NATs."


      That sounds to me like an environment where IPv6 isn't even deployed.  Why would BACnet/IPv6 be rolled out in this environment, then?  


      6to4 tunnels/servers are specialized pieces of equipment which require special configuration in the same way a NAT requires special configuration.  In my mind, and again I might be missing something, this scenario is solved in BACnet by BACnet routing.  In the case where you'd want a B/IPv6 network to communicate with B/IPv4 devices you'd use a B/IPv6 to B/IPv4 router which would get configured the same as, say, an MS/TP to B/IPv4 router.  But, a B/IPv6 site deployed over IPv4 infrastructure doesn't seem like a viable option.  




      From: bacnet-ip-wg@yahoogroups.com [mailto:bacnet-ip-wg@yahoogroups.com] On Behalf Of cliffcopass
      Friday, August 19, 2011 12:12 PM
      [bacnet-ip-wg] Asked an IT person about IPv6 multicast



      I recently asked an IT person about IPv6 multicast related to BACnet and got the following answer:

      The BACnet committee was concerned about whether IT departments would configure their infrastructures such that the IPv6 version of BACnet could utilize multicast messages. These message types allow for 'concentric areas' of reachability among the BACnet hosts.

      Reply from a person with IT and IPv6 experience:
      There is no universal yes/no to this question, since mandates and regional factors play some part in influencing change. IT departments in US government agencies are mandated to enable IPv6 in a push to enable reachability to intelligent devices within government agencies and even down to equipment on the battlefield. Likewise companies in Asia and Europe tend to embrace IPv6 due to the limited access of public IPv4 addresses with those regions of the world.

      At many NA companies, routers are not setup to allow IPv6 link local addresses, but tunneled IPv6 techniques could be deployed (but rarely implemented). It might take years to enable IPv6 in the building routers and add AAAA records to DNS. IT configuration changes require: approval; planning; and commission effort that isn't readily justified. Some companies have run out of uniquely addressable IPv6 address. IT managed PCs may have NATed IPv4 addresses because there were duplicate address conflicts. When devices are NATed there is an even higher likelihood that address duplication can occur - and NATs will tend to block streaming point-to-point applications unless a NAT traversal protocol is applied. NATs also over-complicate the messy IPv4 routing tables that have to be maintained in each router. Larger routing tables mean slower response latencies, consume more memory in the router (and in some cases require router upgrade). For the moment, IT departments in NA are passing the pain onto their network users who typically are aware that their application performance is degrading - but really don't have the skills or time to realize that poor network throughput is the root cause.

      IT departments won't be willing to change anything to support BACnet. Therefore consider the worst case scenario whereby the entire IT managed infrastructure only supports IPv4 routers, DNS (A records only), and NATs. In that case, adding 6to4 tunneling broker at each BBMD/Router (per 135-2004 Addendum o Accommodates remote operator access via Annex J BACnet/IP through NAT firewalls.) would allow IPv6 packet traversal to any and all legacy IPv4 subnets which included this 6to4 tunneling feature.

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