Hi Ole, See inline.
Cheers, Ian >Ian, > >> Sorry to dig this one up again, but although there has been a fair bit >>of discussion around the topic, I don't think that we have so far >>reached an agreement on how to provision sw CPEs with the address of the >>concentrator for MAP-E and lw4o6. We need to get a final answer on this >>as there's a few drafts (softwire-unified-cpe, softwire-map-dhcp, >>softwire-lw4over6) that are relying on it. >> >> To try and summarise what's already out there: >> The Unified CPE & lw4o6 drafts propose the use of DHCPv6 Option 64 (the >>DS-Lite AFTR FQDN option) >> Map-dhcp describes the use of the default mapping rule (DMR) to provide >>the /128 of the BR >> >> I think that it's reasonable to say that both work I.e. They contain >>enough information to provision the client with the /128 of the >>concentrator so that it can send traffic. >> >> Here are the arguments for/against each that I've seen. I've tried to >>list all the ones that I've seen, so if I've missed any, then please add >>them: >> >> DHCPv6 Option 64 >> Pros >> FQDN means that DNS round-robin load balancing could be used > >RFC6334 specifies that only the first AAAA should be used. [ian] Checking 6334 section 5 - "If any DNS response contains more than one IPv6 address, the B4 system picks only one IPv6 address and uses it as a remote tunnel endpoint for the interface being configured in the current message exchange." So you could use Option 64/DNS to provision multiple endpoints. You'd need another mechanism (e.g. The bfd model) to detect failure and take advantage of it, though. > >> Reuse of an existing option >> >> Cons >> Can not be extended with additional sub-options > >the CE needs to deal with DNS TTL and the added complexity of having the >resulting "lifetime" of the >default router be different than the lifetime of the address/mechanism. > >only one BR can be configured > >> map-dhcp DMR >> Pros >> Option has an 'encapsulated options' field, so could be extended with >>additional functionality (although no additional functionality has >>currently been proposed at this stage) >> >> Cons >> Only one DMR /128 can be provisioned to a client, so round robin load >>balancing can't be used > >you can use anycast. [ian] You can. But then, why do you need the list of addresses suggested below? > >> May conflict with the MAP-T (</128 prefix) DMR Could be considered to >>be out of scope for this discussion, but if we are following the >>mechanisms described in Unified CPE so that a CPE can work out which SW >>mode to configure, then a dedicated MAP-T sub-option (not shared by any >>other mode) is needed. This is related to conversations that I've had >>around extending the Unified CPE model for other softwire approaches. >> >> My view: If there is additional functionality required in this option, >>over an above the provisioning of a /128 prefix for the concentrator, >>then the MAP DMR (limited to MAP-E) is the clear choice. However, if no >>such functionality is needed, then we should re-use Option 64. > >does anyone know why a FQDN (with restrictions) was chosen for DS-lite? > >considerations: > - MAP: should BR be inside or outside of the domain. if inside use an >IPv4 address, if outside use an IPv6 address. > (I believe we have agreed on outside, and for LW46 it must always be >outside). [ian] I think it's simpler just to use outside as a single approach. > - should the CE have multiple BRs? and if so, what should it do between >them? load-balance? > the choice in 6rd was to allow for multiple BRs, but not specify how >multiple BRs could be used > >my preference is for a simple list of IPv6 BR addresses. i.e. none of the >two above options. [ian] As long as this is done as a separate option to the DMR, then I think this would work. > >cheers, >Ole _______________________________________________ Softwires mailing list [email protected] https://www.ietf.org/mailman/listinfo/softwires
