use of port 53 is for zone transfers between dns servers and for when dns tries to mux up traffic over tcpmux service on tcp port 1. if one is defining what dns traffic to allow internally trhen in order to prevent a bunch of needless coding include tcp port 53 in your plans else you aewe asking for resolution problem down the road. 4.2.2. TCP usage Messages sent over TCP connections use server port 53 (decimal). The message is prefixed with a two byte length field which gives the message length, excluding the two byte length field. This length field allows the low-level processing to assemble a complete message before beginning to parse it. this is an advantage as this extends the bogus 512 byte limit set by udp. as far as connectivity management, the dns server should not block other activities waiting for TCP data and should support multiple connections, should assume that the client will initiate close a dormant connection to reclaim resources, it wait 120 seconds of idle time before killing the connex. -----Original Message----- From: netfilter-bounces@xxxxxxxxxxxxxxxxxxx [mailto:netfilter-bounces@xxxxxxxxxxxxxxxxxxx]On Behalf Of Mark-Walter@xxxxxxxxxxx Sent: Tuesday, November 09, 2004 11:02 AM To: netfilter@xxxxxxxxxxxxxxxxxxx Subject: RFC 1035 Bind Hi, there's quite a lot to read about open UPD and TCP port for DNS queries. I read an article from a tech guru from microsoft as follow:-) http://certcities.com/editorial/columns/story.asp?EditorialsID=144&page=2 As I understand RFC 1035 answering packet's over TCP are truncated at a limit of 512 bytes but it could be more ... Isn't it the comparing this document the best way while using UDP to DROP TCP packets over port 53 and to allow only UDP port 53 at it does not use the IP protocol ? Ok, I know there could be a problem in the inside of a webserverfarm and you need to allow both protocols and he is refering to this but generally I would like prefer to avoid TCP over port 53 concerning to avoid a man-in-the-middle attack. -- Best Regards, Mark. "Hello, I am brand new to meditation, and I have a frustrating habit of falling asleep in class. I don't know how to stop this. When my teacher tells us to relax our bodies and focus on breathing, my body relaxes, but so does my brain."
