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</o:shapelayout></xml><![endif]--></head><body lang=ZH-CN link=blue vlink=purple style='text-justify-trim:punctuation'><div class=WordSection1><p class=MsoNormal><span lang=EN-US>Hi folks, <o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>I recently notice a issue on source-based DNS policy in dual-stack networks. (Maybe I missed some solution or best practice already existed.)<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>It may be well known that some networks use multiple upstream ISPs to share the load (Universities for example). There are many options to do this. One option is to use DNS resolver to response with different answers to different group of users, which will finally steal the traffic to different ISPs. It works very well in IPv4-only network, because the resolve can implement the load-balance policy based on IPv4 source address. However, in dual-stack environment a client may query A via IPv6 or AAAA via IPv4 which makes this load-balance option difficult. It is become a reason some network administrators become reluctant to upgrade their resolver to dual-stack. <o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>Besides the resolver, authority server who player smart DNS function (response differently according to clients geo-location address) suffers as well. Current RFC7871 give some clue that DNS massages can carry subnet information of end users, but it is fit the scenario from resolver to authority. And the resolver still have no way to know other IPv6(or IPv4 ) addresses of their users when they are speaking different language(I mean IP version).<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>Is it a qualified problem statement? <o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>Best regards,<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>Davey<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p></div></body></html>