name resolution

[Xen]

Nils Kassube schreef op 24-11-2017 19:10:
> Xen wrote:
>> Nils Kassube schreef op 24-11-2017 18:37:
>> > So if they decide to assign the
>> > network name you used for a decade+ on your LAN to whatever purpose,
>> > it is up to you to either change the name or live with some things
>> > not working as expected.
>> 
>> Please link this ICANN decision.
> 
> It is a RFC: <https://tools.ietf.org/html/rfc6762>. So maybe ICANN
> wasn't involved.

Well thank you.

You realize it says right in the beginning:

Multicast DNS (mDNS) provides the ability to perform DNS-like
    operations on the local link ___in the absence of any conventional
    Unicast DNS server___.

Emphasis mine?

"Any DNS query for a name ending with ".local." MUST be sent to the
    mDNS IPv4 link-local multicast address 224.0.0.251 (or its IPv6
    equivalent FF02::FB)."

This goes directly against the above statement.

"Implementers MAY choose to look up such names concurrently via other
    mechanisms (e.g., Unicast DNS) and coalesce the results in some
    fashion."

But we have freedom again.

So you see the Ubuntu/Debian/everywhereelse solution is not mandated by 
the RFC ;-).

"Implementers choosing to do this should be aware of the
    potential for user confusion when a given name can produce different
    results depending on external network conditions (such as, but not
    limited to, which name lookup mechanism responds faster)."

However this confusion would not arise if you augment it with a *local* 
DNS server such as embedded in any router or networking device.

"DNS queries for names that do not end with ".local." MAY be sent to
    the mDNS multicast address, if no other conventional DNS server is
    available.  This can allow hosts on the same link to continue
    communicating using each other's globally unique DNS names during
    network outages that disrupt communication with the greater 
Internet."

Does not allude to the possibility of internal DNS servers.

Yes I know installing dnsmasq is extremely technical, however installing 
mdns by default on all computers is no different.

It places the solution in the resolver instead of in the router.

The rest of the document has no relevance to traditional unicast.

So it is clear that the RFC does not mandate an uncompromising attitude.

It only requests that all hosts support mDNS.

It does not say that they cannot also support regular unicast DNS,

either in preference, non-preference, or equal-weight operation.

An implementation may choose...


But you catch the drift.

It says nowhere that .local is to be used exclusively for multicast.

In fact, it says the opposite.

So thank you for that.