using TCP53 for DNS

Wed Apr 27 07:26:44 UTC 2005

On Tue, Apr 26, 2005 at 03:04:25PM -0400,
 Patrick W. Gilmore <patrick at ianai.net> wrote 
 a message of 46 lines which said:

> I am interested in how many name servers - caching or authoritative
> - are filtering incoming and/or outgoing TCP port 53.

For authoritative name servers of TLD, you can browse:

http://www.generic-nic.net/dyn/mon/

And see that incoming TCP is often filtered, even on serious TLD:

w: Server doesn't listen/answer on port 53 for TCP protocol

    * Ref: IETF RFC1035 (p.32 4.2. Transport)

      The DNS assumes that messages will be transmitted as datagrams or in a byte stream carried by a virtual circuit. While virtual circuits can be used for any DNS activity, datagrams are preferred for queries due to their lower overhead and better performance.

    * ns.cnc.ac.cn./159.226.1.1
    * ns.cernet.net./202.112.0.44