[dns-operations] dns loop

[william(at)elan.net]

I'm curious if someone would like to make a comment about the output 
below...

Now, when writing my own resolver how fast should I timeout if
it appears to be a loop and should I just detect and not try in
the first place if I'm directed to server that already answered
the query (or should I try another server in the same NS list)?

What kind of error is it appropriate to signal back for caching
resolver in case of a loop?

----------------------------------------------------------------------

$ dig +trace 225.225.225.225.in-addr.arpa

; <<>> DiG 9.2.5 <<>> +trace 225.225.225.225.in-addr.arpa
;; global options:  printcmd
.                       15743   IN      NS      C.ROOT-SERVERS.NET.
.                       15743   IN      NS      D.ROOT-SERVERS.NET.
.                       15743   IN      NS      E.ROOT-SERVERS.NET.
.                       15743   IN      NS      F.ROOT-SERVERS.NET.
.                       15743   IN      NS      G.ROOT-SERVERS.NET.
.                       15743   IN      NS      H.ROOT-SERVERS.NET.
.                       15743   IN      NS      I.ROOT-SERVERS.NET.
.                       15743   IN      NS      J.ROOT-SERVERS.NET.
.                       15743   IN      NS      K.ROOT-SERVERS.NET.
.                       15743   IN      NS      L.ROOT-SERVERS.NET.
.                       15743   IN      NS      M.ROOT-SERVERS.NET.
.                       15743   IN      NS      A.ROOT-SERVERS.NET.
.                       15743   IN      NS      B.ROOT-SERVERS.NET.
;; Received 324 bytes from 216.151.192.1#53(216.151.192.1) in 4 ms
225.in-addr.arpa.       86400   IN      NS      NS.ISI.EDU.
225.in-addr.arpa.       86400   IN      NS      NIC.NEAR.NET.
225.in-addr.arpa.       86400   IN      NS      FLAG.EP.NET.
225.in-addr.arpa.       86400   IN      NS      STRUL.STUPI.SE.
;; Received 178 bytes from 192.33.4.12#53(C.ROOT-SERVERS.NET) in 31 ms
225.in-addr.arpa.       84506   IN      NS      NS.ISI.EDU.
225.in-addr.arpa.       84506   IN      NS      NIC.NEAR.NET.
225.in-addr.arpa.       84506   IN      NS      FLAG.EP.NET.
225.in-addr.arpa.       84506   IN      NS      STRUL.STUPI.SE.
;; Received 282 bytes from 128.9.128.127#53(NS.ISI.EDU) in 92 ms
225.in-addr.arpa.       84506   IN      NS      NS.ISI.EDU.
225.in-addr.arpa.       84506   IN      NS      NIC.NEAR.NET.
225.in-addr.arpa.       84506   IN      NS      FLAG.EP.NET.
225.in-addr.arpa.       84506   IN      NS      STRUL.STUPI.SE.
;; Received 282 bytes from 128.9.128.127#53(NS.ISI.EDU) in 23 ms
225.in-addr.arpa.       84506   IN      NS      NS.ISI.EDU.
225.in-addr.arpa.       84506   IN      NS      NIC.NEAR.NET.
225.in-addr.arpa.       84506   IN      NS      FLAG.EP.NET.
225.in-addr.arpa.       84506   IN      NS      STRUL.STUPI.SE.
;; Received 282 bytes from 128.9.128.127#53(NS.ISI.EDU) in 23 ms
225.in-addr.arpa.       84506   IN      NS      NS.ISI.EDU.
225.in-addr.arpa.       84506   IN      NS      NIC.NEAR.NET.
225.in-addr.arpa.       84506   IN      NS      FLAG.EP.NET.
225.in-addr.arpa.       84506   IN      NS      STRUL.STUPI.SE.

...

;; Received 282 bytes from 128.9.128.127#53(NS.ISI.EDU) in 53 ms
225.in-addr.arpa.       84158   IN      NS      NS.ISI.EDU.
225.in-addr.arpa.       84158   IN      NS      NIC.NEAR.NET.
225.in-addr.arpa.       84158   IN      NS      FLAG.EP.NET.
225.in-addr.arpa.       84158   IN      NS      STRUL.STUPI.SE.
;; Received 282 bytes from 128.9.128.127#53(NS.ISI.EDU) in 23 ms
225.in-addr.arpa.       84158   IN      NS      NS.ISI.EDU.
225.in-addr.arpa.       84158   IN      NS      NIC.NEAR.NET.
225.in-addr.arpa.       84158   IN      NS      FLAG.EP.NET.
225.in-addr.arpa.       84158   IN      NS      STRUL.STUPI.SE.
dig: Too many lookups