[afnog] IIS & DNS

[Mark Tinka]

On Tuesday 07 March 2006 19:11, Brian Candler wrote:

> IIS probably calls the Windows resolver library, and
> the resolver library will make a DNS query.

It actually looks like Microsoft SMTP (which IIS uses to 
send e-mail) will only make DNS queries on TCP port 53, 
even though the size of the query response is < 512 
bytes.

> It can use 
> either UDP or TCP port 53. Normally resolvers don't
> choose TCP unless the response to a query is very
> large. However they are quite entitled to use TCP if
> they wish, which means it's not a good idea for your
> firewall to block this usage of DNS.

Okay.

Cheers,

Mark.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 827 bytes
Desc: not available
Url : http://listserv2.cfi.co.ug/pipermail/afnog/attachments/20060308/839e22e0/attachment.bin