Re: A mechanism to encode HTTP version information in DNS

[Amos Jeffries <[e-mail]>]

On 15/02/2013 9:16 a.m., Phillip Hallam-Baker wrote:
> Encoding HTTP version information in DNS is easy if you don't 
> particularly care about using DNS properly or want to do anything more 
> than encode HTTP version information.
>
> Doing it well gets rather more complex. A DNS query costs a round trip 
> so you would ideally like to make it pay. Also the process of 
> deploying DNS records takes some time and it is better to reuse an 
> existing record but only if that will not create ambiguity.
>
> Looking again at the URI record, I think that we could use it to 
> provide a HTTP version flag and other useful features in the DNS. In 
> particular we can use the URI record to effect a HTTP redirect in DNS 
> (a UDP round trip) rather than require a TCP round trip. It also 
> provides for fault tolerance and load balancing and works well with 
> Web Services.

One small note on this assertion:
   FQDN are capable of being anything up to 256 octets long *per-label*. 
When the FQDN is greater than 250 octets or so this will add both a UDP 
round trip plus a TCP round trip, on top of the final connection setup 
round trip. This may not seem a critical point, but we are already 
encountering web sites and services with >64 octet FQDN in public 
traffic which is causing TLS certificate issues.


That asside, I am liking this proposal better than any of the earlier 
DNS proposals. I can forsee support from Squid being implemented if this 
is selected to go ahead.

Amos