Fred, > As a first comment, the document is lacking a discussion of the > implications of having the BR use its anycast address as the source > address for the packets it relays. > > Take for example the case of two BRs A and B that configure the > same IP anycast address, and a CE router C within the 6rd domain. > If BR A forwards packets toward C, but the packets are lost in the SP > network, any resulting ICMPs could just as easily flow back through > BR B instead of A. Then, if the ICMPs don’t contain enough information > for translation, BR B has no way to send a translated message back > to the original source and a black hole can result.
BRs are stateless. it does not matter which one the ICMP comes back to. if the ICMP message doesn't contain enough of the IPv6 packet there is nothing it can do, regardless of which one got the ICMP message. the use of the anycast address doesn't change that. this exact issue shouldn't cause any issues. I've tried to think of any other issue with using the anycast as the source address, but I haven't come up with any. please let us know if you have others! > A solution to this would be to have BR’s use their unicast address as > the source instead of an anycast address. In that case, CE router > C simply needs a way to discover the unicast addresses of all BRs > in the domain that configure the same anycast address. Such discovery > could be via the DHCP option, via DNS resolution of a FQDN, etc. cheers, Ole _______________________________________________ Softwires mailing list [email protected] https://www.ietf.org/mailman/listinfo/softwires
