[Info-vax] Telnet problems

[jbriggs444]

On Feb 17, 11:38 am, Dave <Baxt... at tessco.com> wrote:
> On Feb 17, 8:04 am, Steven Schweda <sms.antin... at gmail.com> wrote:
>
> > Bob Gezelter wrote:
> > > Some important discriminators:
> > > - if the machine is identified by numeric IP address from a different
> > > system, is the delay still there
>
> >    If the problem is a failing _reverse_ DNS look-up of the
> > client by the _server_, then it probably won't matter how the
> > _client_ identifies the server.
>
> >    This suggestion is frequently made, but seldom helps.  It's
> > rare for there to be a big delay in the original DNS look-up
> > of the server by the client (which finally succeeds), but
> > that's what is tested by doing "telnet ip.address" instead of
> > "telnet "name".
>
> Another cause for this kind of delay is that there maybe more than one
> DNS server defined, and the first is non-responsive.     The DNS
> servers are often queried "round-robin" style, with a timeout involved
> between each query.     If the first is unresponsive, the process must
> wait until the timeout expires before the query is sent to the next,
> etc., etc.
>
> Just a thought.
>
> Dave.

Reasonable thought.  And I'd buy it for an intermittent delay in the
2-10 second range.

A consistent delay of one minute and five seconds sounds close to a
cumulative delay of a 2 + 4 + 8 + 16 + 32 = 62 second exponential
backoff scheme.  That'd be pretty standard for a DNS lookup in the
face of a dead server.