>> On 13 May 2016, at 9:02 AM, Roger Clarke <[email protected]> wrote: >> Is the largest provider in the country utterly incompetent? >> Or is there something important about Internet architecture that I fail to >> understand?
At 9:08 +1000 13/5/16, Avi Miller wrote: >It's most likely that Telstra are AnyCasting their DNS servers: >https://en.wikipedia.org/wiki/Anycast >Essentially this means that they have a single IP address that is routed to >the nearest actual DNS server to the requester. And that there can be lots and >lots of backends for this. Thanks for this! However, following through to RFC3258 https://tools.ietf.org/html/rfc3258 it seems that redundancy, and hence accessibility when the primary DNS-server is unreachable, was *not* a motivation for the application of Anycasting to the DNS: "The primary motivation for the development and deployment of these practices is to increase the distribution of Domain Name System (DNS) servers to previously under-served areas of the network topology and to reduce the latency for DNS query responses in those areas" And, as I understand it, the first backbone router, where BGP comes into play, should intercept the packet addressed to the Telstra name-server, and substitute an IP-address based on its internal table. If Anycasting is in use, and the Telstra name-servers were unreachable, then presumably either the BGP tables were polluted, or *all* of the net-near name-servers were out of action. (Or even *all* of the name-servers were out of action, if the process is clever enough to detect that the net-near ones aren't responding and then sends packets to net-distant servers). Either way, it still seems like incompetence on Telstra's part. (And the speed with which it was fixed suggests that there could have been a pre-programmed solution to whatever the underlying cause was, had they bothered to implement it). -- Roger Clarke http://www.rogerclarke.com/ Xamax Consultancy Pty Ltd 78 Sidaway St, Chapman ACT 2611 AUSTRALIA Tel: +61 2 6288 6916 http://about.me/roger.clarke mailto:[email protected] http://www.xamax.com.au/ Visiting Professor in the Faculty of Law University of N.S.W. Visiting Professor in Computer Science Australian National University _______________________________________________ Link mailing list [email protected] http://mailman.anu.edu.au/mailman/listinfo/link
