[LINK] RFI: Telstra DNS outage

[Roger Clarke]

>> On 13 May 2016, at 9:02 AM, Roger Clarke <Roger.Clarke at xamax.com.au> 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
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Visiting Professor in the Faculty of Law            University of N.S.W.
Visiting Professor in Computer Science    Australian National University