cache dns server use tcp to query other dns server

[Alex Tang]

fyi

at the frist time, it should query the mx record of a domain gsncashgames-news.com

-----Original Message-----
From: bind-users-bounce at isc.org [mailto:bind-users-bounce at isc.org]On Behalf Of Alex Tang
Sent: Friday, January 06, 2006 4:53 PM
To: Barry Margolin; comp-protocols-dns-bind at isc.org
Subject: RE: cache dns server use tcp to query other dns server
Importance: High


I use the snoop on my cache dns server and find out follow things

my cache dns server query other dns server ( ns3.texasdns.com) it return 27 answer 

IP:   Source address = 69.56.15.2, ns3.texasdns.com
IP:   Destination address = x.x.x.x, (my cache dns server)
IP:   No options
IP:   
UDP:  ----- UDP Header -----
UDP:  
UDP:  Source port = 53
UDP:  Destination port = 50538 
UDP:  Length = 47 
UDP:  Checksum = 2852 
UDP:  
DNS:  ----- DNS Header -----
DNS:  
DNS:  Response ID = 61365
DNS:  AA (Authoritative Answer) TC (TrunCation) 
DNS:  Response Code: 0 (OK)
DNS:  Reply to 1 question(s)
DNS:      Domain Name: gsncashgames-news.com.
DNS:      Class: 1 (Internet)
DNS:      Type:  15 (Mail Exchange)
DNS:  
DNS:  27 answer(s)

ETHER:  ----- Ether Header -----
ETHER:  
ETHER:  Packet 3 arrived at 15:37:49.98


after that my cache dns server try to use tcp but have some problem


IP:   ----- IP Header -----
IP:   
IP:   Version = 4
IP:   Header length = 20 bytes
IP:   Type of service = 0x00
IP:         xxx. .... = 0 (precedence)
IP:         ...0 .... = normal delay
IP:         .... 0... = normal throughput
IP:         .... .0.. = normal reliability
IP:   Total length = 41 bytes
IP:   Identification = 58703
IP:   Flags = 0x4
IP:         .1.. .... = do not fragment
IP:         ..0. .... = last fragment
IP:   Fragment offset = 0 bytes
IP:   Time to live = 64 seconds/hops
IP:   Protocol = 6 (TCP)
IP:   Header checksum = 33c1
IP:   Source address = x.x.x.x, my cache dns server
IP:   Destination address = 64.202.167.159, ip-64-202-167-159.secureserver.net
IP:   No options
IP:   
TCP:  ----- TCP Header -----
TCP:  
TCP:  Source port = 50931
TCP:  Destination port = 53 (DNS)
TCP:  Sequence number = 858230409
TCP:  Acknowledgement number = 3084354847
TCP:  Data offset = 20 bytes
TCP:  Flags = 0x10
TCP:        ..0. .... = No urgent pointer
TCP:        ...1 .... = Acknowledgement
TCP:        .... 0... = No push
TCP:        .... .0.. = No reset
TCP:        .... ..0. = No Syn
TCP:        .... ...0 = No Fin
TCP:  Window = 25192
TCP:  Checksum = 0x21da
TCP:  Urgent pointer = 0
TCP:  No options
TCP:  
DNS:  ----- DNS:   -----
DNS:  
DNS:  ""
DNS:  

it only try to query DNS:  "". Why ? Is it normal . fyi my firewall only allow our clients ip to query the cache dns server high port. and only established tcp is allowed to come into the segment. 

Do i miss some configuration ?

-----Original Message-----
From: bind-users-bounce at isc.org [mailto:bind-users-bounce at isc.org]On Behalf Of Barry Margolin
Sent: Friday, January 06, 2006 2:24 PM
To: comp-protocols-dns-bind at isc.org
Subject: Re: cache dns server use tcp to query other dns server


In article <dpkon2$ms1$1 at sf1.isc.org>,
 "Alex Tang" <alextang at cms.hkcable.com> wrote:

> or if my cache dns server cannot get answer from other dns server by udp , 
> will my cache dns server change to use tcp to query the no answered other dns 
> server  ?

No, BIND doesn't do that.  It only uses TCP for ordinary queries when 
the UDP attempt returns a truncated response.

-- 
Barry Margolin, barmar at alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***
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