Hi Remi, I think I mis-read Figure 1 in your draft. As I read this, I think the current design will completely rely on dhcp to manage the v4 prefix. Yes, this decouples the v4 and v6 addresses, but this will add additional operation effort on dhcp. Also, if an ISP has many small IPv4 prefixes they want to use in 4rd, it will require to provision all of them to the BR. This may be ok for some operators, but not all operators.
In term of single or multiple 4over6 concentrators, I don't see people will advertise the same PI from two far away concentrators. So the return packet will also go back to the same (or close) concentrator. That said, I agree that stateless is always easier for HA. I have no disagreement on this. In the end, they have pros and cons. Based on the ISP's requirements, it is just a matter of choice. Cheers, /Yiu On 4/6/11 5:19 PM, "Rémi Després" <[email protected]> wrote: >Yiu, > >I am not sure we completely understand each other here. >Please tell me if what I write is insufficiently clear. > >Le 6 avr. 2011 à 21:06, Lee, Yiu a écrit : > >> Hi Remi, >> >> On 4/6/11 10:04 AM, "Rémi Després" <[email protected]> wrote: >> >>> Partially agreed. >>> - If all IPv6 customers are given the same number of IPv4 ports, 4rd >>> doesn't imply anything on Pv6 routing., >>> - If there are several 4over6 concentrators, there are constraints on >>>the >>> IPv6 routing to ensure satisfactory load sharing between them with >>>stable >>> routes. >>> - Furthermore, if these concentrators are far from one another, they >>> imply that the IPv4 backbone ensures symmetric routing so that all >>>return >>> traffic from a concentrator comes back to it. >> >> I think we are on the same page. What I meant is in the case of stateful >> 6to4, IPv6 address won't contain any IPv4 address in the prefix. That >> won't require coupling between the IPv4 and IPv6 prefixes. It may or may >> not be a problem for some operators. > >IPv6 prefixes of 6rd don't contain IPv4 embedded addresses (they differ >in this respect from the stateless A+P described in the aplusp draft). >With 4rd, if all CE's get IPv6 prefixes having the same length, and are >assigned the same number of IPv4 ports, the IPv6 routing is taken as is. >It is only after that that one or a few mapping rules, whose parameters >can be advertised in stateless DHCPv6, define how each CE derives its >shared IPv4 address and port set from its IPv6 prefix. > >> LB is a different issue. It doesn't relate to address coupling. That >>said, >> it isn't so straight forward for stateless approach because it depends >>on >> the placement of the BR and the v6 routing to the anycast address. > >Routing of the IPv6 network can be reconfigured at any time without >breaking connections. >Load balancing can be performed without any concern for packets of each >connection having to go to the same BR, which makes it simpler. > > >> For stateful 4to6, the outgoing and incoming v4 traffic are symmetric >> because all v4 traffic must traverse the concentrator. I don¹t see why >>the >> backbone has to do something special for it. > >If there is only one concentrator, no problem. >But if there are several widely separated concentrators, and they are >reachable at the same PI prefix at the border between the IPv6-only >network and the IPv4 backbone, then there is a return path problem. > >RD > >PS: I may be able to continue tomorrow, but then will be unreachable >until April 25. > > > > _______________________________________________ Softwires mailing list [email protected] https://www.ietf.org/mailman/listinfo/softwires
