dns header doubt

[Mark Andrews]

> hi folks,
> i have some basic doubts regarding dns header.
> as we know there are 2 flags Recursion desired(RD) and Recursion available
> (RA) . RD is used by the client in any dns request and RA is used by the
> server in the response. RD does not make any sense to server and RA for
> client . so why 2 separate flags are used to denote these 2 requirements ?
> couldnt it be managed by only one flag? what is actual reasons for keeping 2
> separate flags instead of only one?
> --
> Raghav.S.N

	Well this is not really the place to discuss protocol changes.
	namedroppers at ops.ietf.org is more appropriate.
	
	RD tells the server what to do.  It is copied to the reply.
	RA tells the client what the server is willing to do.

	Having both come back in a repli means that you can just display
	the reply.  Also if RD w/o RA comes back you are almost always
	talking to the wrong server if you are a stub resolver.

	Mark
--
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark_Andrews at isc.org