Re: [tae] New draft: announcing the supported transports via DNS

[Caitlin Bestler <[e-mail]>]

On Sep 18, 2009, at 11:20 AM, Joe Touch wrote:

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> Dan Wing wrote:
>>
>>
>>> -----Original Message-----
>>> From: [e-mail] [mailto:[e-mail]] On
>>> Behalf Of Joe Touch
>>> Sent: Friday, September 18, 2009 8:23 AM
>>> To: Michael Welzl
>>> Cc: [e-mail]
>>> Subject: Re: [tae] New draft: announcing the supported
>>> transports via DNS
>>>
>>
>>
>> Michael Welzl wrote:
>>>>> Hi all,
>>>>>
>>>>> This discussion reminds me of something else:
>>>>> someone (I think Jana?) mentioned the possibility of negotiating
>>>>> more than just the transport protocol, e.g. even the usage of  
>>>>> IPv6,
>>>>> with a negotiation protocol.
>>>>>
>>>>> I recently talked about this with someone who knows more about
>>>>> IPv6 than me (actually not hard to find such a person!), and that
>>>>> someone said that a standard is already in place for determining
>>>>> whether IPv6 can be used **via DNS**.
>> That presumes two things:
>>
>> a) you know which protocol to use to get to the DNS
>>
>> b) not everybody uses the DNS, at which point you definitely need to
>> know the address format since you need to know the address
>>
>>> Not everybody uses TCP, either.  For example, RTP is commonly
>>> sent over UDP and the IPv4 addresses are commonly signaled in
>>> SDP as IPv4 address literals.  So RTP doesn't use DNS or TCP.
>>
>>> But DNS-less and TCP-less applications or usage are not the
>>> 80% that is the interesting problem.  I can't maintain
>>> host tables for the Internet anymore -- it's too big.  The need
>>> for DNS is more acute with long and awkward IPv6 addresses.
>
> As you note, addresses are sometimes used for non-human purposes, and
> with IPv6 they could be created on the fly - I wouldn't want to have  
> to
> wait to register them in the DNS vs exchanging them in-band.
>


Of course if you have already used application specific mechanisms to  
exchange
IP addresses in-band then you obviously have the means to specify which
transport protocol and options to use as well.

That still leaves discovery via limited DNS, urls with literal IP  
addresses, discovery
by other administrative means and local discovery mechanisms such as  
zeroconf.



Does anyone know what impact DNS caches would have on a DNS based  
solution?
Are the entire set of DNS records for a domain routinely cached?



--
Caitlin Bestler
[e-mail]
http://www.asomi.com/CaitlinBestlerResume.html