Darcy Kevin (FCA)
kevin.darcy at fcagroup.com
Sat Aug 13 00:11:26 UTC 2016
True, strictly from a per-hop latency standpoint, there shouldn't be much difference between forwarding a packet or forwarding a DNS query.
Having said that -- and I'm sure the BIND developers could elaborate further on this -- I know that there's big difference between processing *packets*, from, say, a routing standpoint, which customized ASIC-level hardware can do to the tune of millions per second, and processing *queries*, which are much higher-level constructs, with a lot more variation, more levels of parsing, disassembly, re-assembly, validation, etc. When you have multi-hop DNS forwarding, you're using up significant resources on multiple computing devices at once, in ways that don't necessarily lend themselves to optimization in hardware. It ends up being the opposite of parallelism, i.e. using the resources of multiple devices to accomplish something that could, with only configuration changes, be accomplished with the resources of only one device.
At the risk of sounding xenophobic, there seems to be a mindset among certain cultures that forwarding is "natural", and, in contrast, having DNS instances talk to each other directly is somehow "artificial". I've had this conversation many times with many of my European counterparts over the years, and we just seem to view things differently. One could speculate on the difference in world view -- submission to higher authority, perhaps? Hierarchical social organization? I don't know -- I don't claim any expertise whatsoever in sociology, cognitive psychology, or related fields. But for me, and I think most people in my (North American) culture -- possibly because we tend more towards individualism and/or egalitarianism? -- having DNS instances talk *directly* to each other, as "equals" or "peers", is much more natural than one DNS instance relying upon another to handle all of its resolution needs (thus making the first instance subservient, in a sense, to the second), which then relies on another, and to another, and so on, in a daisy chain.
Again, maybe it's just a different mindset/world-view. Or, perhaps I'm over-generalizing a cultural difference from a relatively-small sample of conversations. But, as I touched on in my second paragraph, there may be some objective reasons to eschew forwarding, particularly multi-hop forwarding.
From: bind-users [mailto:bind-users-bounces at lists.isc.org] On Behalf Of Willmann, Robert
Sent: Friday, August 12, 2016 1:33 AM
To: bind-users at lists.isc.org
Subject: RE: Delegation questions
Kevin Darcy wrote:
> In any case, multi-hop forwarding is always the least-preferred option.
I wonder for which reason do you think this.
Of course, any forwarding adds a additional hop and therefore additional delay and an additional possible point of failure.
But this is true for any network-connection.
So, what do you think are the DNS-specific downsides of forwarding?
The only thing that comes to mind if I think about downsides of forwarding is that, if something goes wrong, the client only gets a generic SERVFAIL as errormessage instead of a specific explanation what exactly went wrong.
Do you see other downsides to forwarding?
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