Re: How long can an NS chain be?

[Masataka Ohta <mohta@necom830.hpcl.titech.ac.jp>]

Dan;

> There's no guarantee in the DNS architecture that this chain will ever
> terminate. In fact, there could be a cycle;

Yes. This is a known problem people want to ignore.

> Suppose, however, that the NS chain does terminate. It could have any
> length. Is it okay for people to set up an NS chain of length 5? 10? 30?
> How far does a resolver have to go? How much memory do implementors have
> to dedicate to a single request? Is it okay for a resolver to give up
> after several steps? How many? Can a resolver ignore NS records without
> glue if there are three NS records with glue? Two? What if those two
> servers are unreachable?

RFC 1034 says:

:   1. Bound the amount of work (packets sent, parallel processes
:      started) so that a request can't get into an infinite loop or
:      start off a chain reaction of requests or queries with other
:      implementations EVEN IF SOMEONE HAS INCORRECTLY CONFIGURED
:      SOME DATA.

How many? It depends.

							Masataka Ohta