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					draft-thaler-ipngwg-multilink-subnets-01.txt

            Dave Thaler
       dthaler@microsoft.com


                IETF 51, IPv6 WG               1
• Presented –00
• Agreed on concepts, motivations
   – A “multilink subnet” is when you have an address
     prefix which spans multiple links, but is routed
     between them at layer three.
• Two models for host view work without changing
  hosts
   – Onlink: hosts use NSs, routers send proxy NAs for
     offlink nodes
   – Offlink: hosts use default routers, routers send
     redirects for onlink nodes
• Presented several possibilities for router
  behavior, many open issues
                       IETF 51, IPv6 WG                  2
• Simple scenarios are simple, complex
  scenarios are complex
  – Should the first spec limit itself to simple
    scenarios? (Complex behavior could take a
    long time)
  – Is it complex to tell the difference?
  – What’s the best way to solve complex
    scenarios?


                    IETF 51, IPv6 WG               3
• How do you handle simultaneous DAD for
  the same address by nodes on different
  links?
• How do you tell the difference between a
  duplicate and a node moving to a different
  link?



                  IETF 51, IPv6 WG             4
• Attempt to classify “simple” vs “complex”
  scenarios, to evaluate solutions
  – Class 1 = single multilink subnet router
  – Class 2 = tree topology
  – Class 3 = arbitrary topology
     • Better(?) classification shortly…
• Moved discussion of router-router
  coordination possibilities to appendix
• Various wording clarifications
                       IETF 51, IPv6 WG        5
• MLSN router has 0 or 1 (or more?) “proxy”
  interfaces, and 1 or more “router”
  interfaces
  – Same scenario as a NAT
  – Same scenario as an IGMP/MLD Proxy
• Does not run any routing protocol
  – Does not support “transit”
  – But does act as an MLD Proxy
• Does simple NS/NA proxying
                  IETF 51, IPv6 WG        6
• On proxy interfaces:
  – Acts like a host with lots of addresses
• On router interfaces:
  – Acts like the (only) default router
  – If it sees an RA from another router, something is
    broken so stop acting as router on this interface
    (either it’s not a simple scenario, or else it was the
    wrong interface type)
• MAY(?): auto-configure which interfaces are
  proxy vs router, based on hearing other RA’s?
                        IETF 51, IPv6 WG                     7
• Single router connecting multiple links in
  an isolated network
  – All interfaces are router-mode interfaces

                    MLSN
                    Router
                R             R
                    R




                     IETF 51, IPv6 WG           8
• Multiple MLSN routers on a shared LAN
  with uplink router(s), with each MLSN
  router having 1+ internal links
  – Proxy-mode on shared LAN
  – Router-mode in private links

               Router            Router


      MLSN              MLSN                MLSN     (NOT TO SCALE)
      Router            Router              Router



                         IETF 51, IPv6 WG                             9
• Internal links sharing same prefix as a
  dialup link

                 Dialup
                 Server




                 MLSN
                 Router



                   IETF 51, IPv6 WG         10
• MLSN router co-exists with others in an arbitrary
  topology
• Must use some router-router coordination
  mechanism
  – Routing protocols or complex proxying rules
• Can co-exist with “simple” MLSN routers
  – Complex box sees simple box as a normal host
  – Simple box sees complex box as a normal router



                      IETF 51, IPv6 WG               11
• Main draft should provide framework for
  both simple and complex, but only specify
  behavior of a simple box
  – Can hopefully get this done quickly
  – Ask that this be a WG document
• Continue work on complex behavior in a
  separate draft


                    IETF 51, IPv6 WG       12
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Description: In order to facilitate expression and identification, IP addresses are expressed in decimal form, such as 210.52.207.2, each expressed as a decimal number can not exceed the maximum 255. IP address consists of two parts, namely, network number (Network ID) and the host number (Host ID). Network number identifies the Internet on a subnet, and host number identifies a subnet of a host. Internet address into two domains, an important advantage to bring: IP data packets from the Internet on a network to another network, select the path can be based on networks rather than hosts. Internet at large, this point was particularly evident advantages, because the routing table instead of only the information stored in the network host information, which can greatly simplify the routing table.