From: Alan Benjamin (abenjami@cisco.com)
Date: Mon Jun 16 2003 - 12:17:29 GMT-3
>Sorry for post again, as I know many of us very confuse on the ISDN timers
>and would like to know (include me :->):
>
>1) What is the different between "dialer enable timeout" and "isdn
>fast-rollover delay"? it seems both are concerning the interval to make
>another new call after the old call torn down. What will trigger the above
>timer?
The "isdn fast-rollover-delay" is typically used to throttle outbound dial
attempts when "dialer load-threshold" triggers an additional call. I've
only used it when dialing BRI to BRI, in order to force a delay (in
seconds) between dial attempts to overcome an issue with how a certain
telco switch handled NI-1 compatibility.
It is important to remember the process by which new calls are generated.
Using legacy DDR as an example (which is what I was using at the time), you
need to include two "dialer map" statements to accommodate the phone
numbers associated with each B channel at the distant end. However, when
"dialer load-threshold" triggers the second call, the "dialer map"
statements are processed in order. This results in a call to the first B
channel that is already busy--and, due to the legitimate call failure, the
second "dialer map" kicks in. (I believe this behavior still exists, but
haven't checked it in a while.)
In my particular case, the remote telco switch would temporarily disable
access to the second B channel while processing the first call attempt (to
the first B channel where I was already connected). My router would then
process the second call attempt, but it would arrive before the switch
returned the second B channel to idle/available--and I would end up with a
Q931 message to the effect of "no channel available." (It's been a long time.)
I hope this helps to clarify the situation.
Take care,
Alan
__________________________________
Alan Benjamin, CCIE #11771
Systems Engineer (AT&T Channel)
Cisco Systems, Inc.
499 Thornall Street, 8th Floor
Edison, NJ 08837
e-mail: abenjami@cisco.com
office: 732-635-3083 cell: 732-742-2694
pager: 800-365-4578 fax: 732-635-3099
__________________________________
at AT&T Middletown (A2-2D03)
office: 732-420-6394
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