How modern Samba handle krb5?

[Jiří Šašek - Solaris Prague]

Hi Experts,
While sniffing packets I have found "net ads join" and "winbindd" 
handles krb5 by such strange way:

No.	Time	Source	Destination	Protocol	Info
47	38.477244	10.163.87.117	10.163.87.58	KRB5	AS-REQ
48	38.478496	10.163.87.58	10.163.87.117	KRB5	KRB Error: 
KRB5KDC_ERR_PREAUTH_REQUIRED
49	38.479156	10.163.87.117	10.163.87.58	DNS	Standard query 0x439f URI 
_kerberos.SMBSETUP.CZECH.SUN.COM
50	38.479597	10.163.87.58	10.163.87.117	DNS	Standard query response 
0x439f No such name URI _kerberos.SMBSETUP.CZECH.SUN.COM SOA 
win-lqmsb4eue0v.smbsetup.czech.sun.com
51	38.479833	10.163.87.117	10.163.87.58	DNS	Standard query 0x0e56 SRV 
_kerberos-master._udp.SMBSETUP.CZECH.SUN.COM
52	38.480165	10.163.87.58	10.163.87.117	DNS	Standard query response 
0x0e56 No such name SRV _kerberos-master._udp.SMBSETUP.CZECH.SUN.COM SOA 
win-lqmsb4eue0v.smbsetup.czech.sun.com
53	38.480366	10.163.87.117	10.163.87.58	DNS	Standard query 0x50be SRV 
_kerberos-master._tcp.SMBSETUP.CZECH.SUN.COM
54	38.480658	10.163.87.58	10.163.87.117	DNS	Standard query response 
0x50be No such name SRV _kerberos-master._tcp.SMBSETUP.CZECH.SUN.COM SOA 
win-lqmsb4eue0v.smbsetup.czech.sun.com

...where Add-DnsServerResourceRecord do not support URI RR-type and also 
the _kerberos-master is not commonly supported in DC. Can Samba still 
work with Windows/based DC?

Older Samba releases were able to respond on err: preauth.required by 
preauthentication so I am curious why the modern Samba will fall into 
such madness in such case. Is there an option to rail even the modern 
Samba back?

Note: on Solaris I am pushed to use MIT krb5 API where my attempts to 
build Samba with Heimdal to check if it will not work breaks on 
conflicts with system headers.

Many thanks,
Jiri