On Nov 19, 2014, at 4:05 AM, Phillip Hallam-Baker <[email protected]> wrote:

> On Wed, Nov 19, 2014 at 2:43 AM, 🔓Dan Wing <[email protected]> wrote:
>> 
>> On Nov 13, 2014, at 10:24 AM, Phillip Hallam-Baker <[email protected]> 
>> wrote:
>> 
>>> I see two distinct use cases:
>>> 
>>> 1) Web browsing
>>> 2) Everything else.
>>> 
>>> The challenges for (1) are latency, latency and latency.
>>> 
>>> Shaving 10ms off the response of a browser is very important to the
>>> Web browser team. Folk can argue that it should not be, but that is
>>> the situation.
>>> 
>>> If we are going to do DNS over TLS then looking at the existing Back
>>> to my MAC protocol makes sense. But the caveat is that does not look
>>> like an application where ultra-low latency is a requirement.
>>> 
>>> 
>>> There are two ways to address the latency issue for Web browsing:
>>> 
>>> 1) Design a protocol tuned for ultra low latency with 1 round trip over UDP.
>>> 2) Combine the DNS requests with other data requests that the browser
>>> would make.
>>> 
>>> Private-DNS takes approach 1
>> 
>> (D)TLS 1.3 takes approach 1 with TLS 1.3, which is optimizing for 0 round 
>> trip (for servers previously used) or 1 round trip (for new servers).
> 
> If its 1 round trip then we are talking about DTLS not TLS.
> 
> The thing I didn't like about using DTLS is that I have to profile
> pretty severely to make the code footprint minimal. And once you
> profile you have to rewrite libraries to only use the profile
> features.

Umkay.  It is good you have personally concluded that a completely new library 
and new protocol is better than profiling DTLS, but I don't yet share that 
conclusion.

> TLS has a stateless session resumption option but it would need to be
> mandatory for DNS over TLS to be viable. And it would have to be
> possible to set decent sized timeouts for the negotiated sessions.

Acknowledged.  However, that requirement for how long to retain 0-RTT 
capability is not unique to DTLS's session resumption.

> On the performance side, PRIVATE-DNS is providing better performance
> for the typical approach of doing an A and a AAAA record lookup in
> parallel since these are typically handled in one request/response
> packet rather than two.

If also SRV and arbitrary other resource records invented in the future, that 
sounds compelling.

-d

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