Why is it slow?

[koancui]

Hi,
I have 2 machines, i configured one of them, such as A, as the
DNS, run named, set B's NS point to A.
When i run telnet B on A, there is obvious delay after
displaying
---------------------------------------
Trying xxx.xxx.xxx.xxx...
Connected to B.
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I had to wait a while here, then got
---------------------------------------
Escape character is '^]'

OS
login:
---------------------------------------

if i set B's NS point a normal DNS, everything is ok.
Can you explain it?
The BIND version is 8.2.2-p5, os is FreeBSD.
Thanx.

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Koan