Re: Microsoft version.binding us now?

[t.kee () F5 COM (Tom Kee)]

                The purpose of the 3-DNS metrics collection software is to measure the path attributes by getting a 
reflection off the requesting end point when a load balancing option is chosen which requires such measurements.   TCP 
half open connection against the requestors port 53 has been a reliable way to garner such a reflection at the expense 
of logging an entry in the messages file.  3-DNS offers administrators several definable and configurable techniques 
which may be used to get a reflection for the purpose of measuring  a round trip time.

>       One such methods is to query the DNS server for its "version.bind". Using version.bind involves a minimal 
> amount of effort for BIND to look up the entry in its' memory tables (for those who wish to refer to the details,  
> look through lines 957-980 in ns_req.c against bind8.2.2pl5 where you'll see that the DNS query is examined for the 
> type TXT, class CHAOS and name "version.bind"). The actual version of BIND returned to a 3-DNS is not examined nor 
> presented to the administrator and no further action is taken. The only importance of this query is the  value 
> collected for  the round trip time. Here somethings you can do.
>
>       To change the version string that is returned by a DNS server, in named.conf add
>
>       options {
>          version "FooBar";
>       };
>
>       To out-right block all replies, in named.conf add
>
>       zone "bind" CHAOS {
>               type master;
>               file "db.bind";
>               allow-query { none; };
>       };
>
>
>       and the actual zone file db.bind
>
>       @       86400   CHAOS   SOA     dns hostmaster.dns.foo.com. (
>                       9 28800 7200 604800 86400 )
>               86400   CHAOS   NS      dns
>       version 86400   CHAOS   TXT     "Anything"
>
>
>
>       The allow-query { none; }; will ensure that no response is returned.
            This   method of round trip time calculation is not pre-configured or a default. Each metrics collection 
method has a       specific timing interval that can be tuned by the administrator to any degree.

                3-DNS does not and will never go beyond the point of it's goal -- to reliably measure network 
performance.

                Regards,

                Tom Kee
                Product Development Manager, 3-DNS
                F5 Networks, Inc.